CINXE.COM

<!DOCTYPE html> <html class="client-nojs vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-sticky-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-toc-available" lang="en" dir="ltr"> <head> <meta charset="UTF-8"> <title>Hyperconjugation - Wikipedia</title> <script>(function(){var className="client-js vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-sticky-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-toc-available";var cookie=document.cookie.match(/(?:^|; )enwikimwclientpreferences=([^;]+)/);if(cookie){cookie[1].split('%2C').forEach(function(pref){className=className.replace(new RegExp('(^| )'+pref.replace(/-clientpref-\w+$|[^\w-]+/g,'')+'-clientpref-\\w+( |$)'),'$1'+pref+'$2');});}document.documentElement.className=className;}());RLCONF={"wgBreakFrames":false,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy", "wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"567c71f7-4e47-43ba-81df-5327c5e5857a","wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"Hyperconjugation","wgTitle":"Hyperconjugation","wgCurRevisionId":1221687648,"wgRevisionId":1221687648,"wgArticleId":2729378,"wgIsArticle":true,"wgIsRedirect":false,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["Articles with short description","Short description is different from Wikidata","Physical organic chemistry"],"wgPageViewLanguage":"en","wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"Hyperconjugation","wgRelevantArticleId":2729378,"wgIsProbablyEditable":true,"wgRelevantPageIsProbablyEditable":true,"wgRestrictionEdit":[],"wgRestrictionMove":[],"wgNoticeProject":"wikipedia","wgCiteReferencePreviewsActive":false,"wgFlaggedRevsParams":{"tags":{ "status":{"levels":1}}},"wgMediaViewerOnClick":true,"wgMediaViewerEnabledByDefault":true,"wgPopupsFlags":0,"wgVisualEditor":{"pageLanguageCode":"en","pageLanguageDir":"ltr","pageVariantFallbacks":"en"},"wgMFDisplayWikibaseDescriptions":{"search":true,"watchlist":true,"tagline":false,"nearby":true},"wgWMESchemaEditAttemptStepOversample":false,"wgWMEPageLength":20000,"wgRelatedArticlesCompat":[],"wgCentralAuthMobileDomain":false,"wgEditSubmitButtonLabelPublish":true,"wgULSPosition":"interlanguage","wgULSisCompactLinksEnabled":false,"wgVector2022LanguageInHeader":true,"wgULSisLanguageSelectorEmpty":false,"wgWikibaseItemId":"Q899217","wgCheckUserClientHintsHeadersJsApi":["brands","architecture","bitness","fullVersionList","mobile","model","platform","platformVersion"],"GEHomepageSuggestedEditsEnableTopics":true,"wgGETopicsMatchModeEnabled":false,"wgGEStructuredTaskRejectionReasonTextInputEnabled":false,"wgGELevelingUpEnabledForUser":false};RLSTATE={"ext.globalCssJs.user.styles":"ready", "site.styles":"ready","user.styles":"ready","ext.globalCssJs.user":"ready","user":"ready","user.options":"loading","ext.cite.styles":"ready","skins.vector.search.codex.styles":"ready","skins.vector.styles":"ready","skins.vector.icons":"ready","jquery.makeCollapsible.styles":"ready","ext.wikimediamessages.styles":"ready","ext.visualEditor.desktopArticleTarget.noscript":"ready","ext.uls.interlanguage":"ready","wikibase.client.init":"ready","ext.wikimediaBadges":"ready"};RLPAGEMODULES=["ext.cite.ux-enhancements","mediawiki.page.media","site","mediawiki.page.ready","jquery.makeCollapsible","mediawiki.toc","skins.vector.js","ext.centralNotice.geoIP","ext.centralNotice.startUp","ext.gadget.ReferenceTooltips","ext.gadget.switcher","ext.urlShortener.toolbar","ext.centralauth.centralautologin","mmv.bootstrap","ext.popups","ext.visualEditor.desktopArticleTarget.init","ext.visualEditor.targetLoader","ext.echo.centralauth","ext.eventLogging","ext.wikimediaEvents","ext.navigationTiming", "ext.uls.interface","ext.cx.eventlogging.campaigns","ext.cx.uls.quick.actions","wikibase.client.vector-2022","ext.checkUser.clientHints","ext.growthExperiments.SuggestedEditSession","wikibase.sidebar.tracking"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.impl(function(){return["user.options@12s5i",function($,jQuery,require,module){mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"}); }];});});</script> <link rel="stylesheet" href="/w/load.php?lang=en&modules=ext.cite.styles%7Cext.uls.interlanguage%7Cext.visualEditor.desktopArticleTarget.noscript%7Cext.wikimediaBadges%7Cext.wikimediamessages.styles%7Cjquery.makeCollapsible.styles%7Cskins.vector.icons%2Cstyles%7Cskins.vector.search.codex.styles%7Cwikibase.client.init&only=styles&skin=vector-2022"> <script async="" src="/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector-2022"></script> <meta name="ResourceLoaderDynamicStyles" content=""> <link rel="stylesheet" href="/w/load.php?lang=en&modules=site.styles&only=styles&skin=vector-2022"> <meta name="generator" content="MediaWiki 1.44.0-wmf.4"> <meta name="referrer" content="origin"> <meta name="referrer" content="origin-when-cross-origin"> <meta name="robots" content="max-image-preview:standard"> <meta name="format-detection" content="telephone=no"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/1/11/Alkene-hyperconjugation2.png/1200px-Alkene-hyperconjugation2.png"> <meta property="og:image:width" content="1200"> <meta property="og:image:height" content="581"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/1/11/Alkene-hyperconjugation2.png/800px-Alkene-hyperconjugation2.png"> <meta property="og:image:width" content="800"> <meta property="og:image:height" content="387"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/1/11/Alkene-hyperconjugation2.png/640px-Alkene-hyperconjugation2.png"> <meta property="og:image:width" content="640"> <meta property="og:image:height" content="310"> <meta name="viewport" content="width=1120"> <meta property="og:title" content="Hyperconjugation - Wikipedia"> <meta property="og:type" content="website"> <link rel="preconnect" href="//upload.wikimedia.org"> <link rel="alternate" media="only screen and (max-width: 640px)" href="//en.m.wikipedia.org/wiki/Hyperconjugation"> <link rel="alternate" type="application/x-wiki" title="Edit this page" href="/w/index.php?title=Hyperconjugation&action=edit"> <link rel="apple-touch-icon" href="/static/apple-touch/wikipedia.png"> <link rel="icon" href="/static/favicon/wikipedia.ico"> <link rel="search" type="application/opensearchdescription+xml" href="/w/rest.php/v1/search" title="Wikipedia (en)"> <link rel="EditURI" type="application/rsd+xml" href="//en.wikipedia.org/w/api.php?action=rsd"> <link rel="canonical" href="https://en.wikipedia.org/wiki/Hyperconjugation"> <link rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en"> <link rel="alternate" type="application/atom+xml" title="Wikipedia Atom feed" href="/w/index.php?title=Special:RecentChanges&feed=atom"> <link rel="dns-prefetch" href="//meta.wikimedia.org" /> <link rel="dns-prefetch" href="//login.wikimedia.org"> </head> <body class="skin--responsive skin-vector skin-vector-search-vue mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject mw-editable page-Hyperconjugation rootpage-Hyperconjugation skin-vector-2022 action-view"><a class="mw-jump-link" href="#bodyContent">Jump to content</a> <div class="vector-header-container"> <header class="vector-header mw-header"> <div class="vector-header-start"> <nav class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-dropdown" class="vector-dropdown vector-main-menu-dropdown vector-button-flush-left vector-button-flush-right" > <input type="checkbox" id="vector-main-menu-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-main-menu-dropdown" class="vector-dropdown-checkbox " aria-label="Main menu" > <label id="vector-main-menu-dropdown-label" for="vector-main-menu-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-menu mw-ui-icon-wikimedia-menu"></span> <span class="vector-dropdown-label-text">Main menu</span> </label> <div class="vector-dropdown-content"> <div id="vector-main-menu-unpinned-container" class="vector-unpinned-container"> <div id="vector-main-menu" class="vector-main-menu vector-pinnable-element"> <div class="vector-pinnable-header vector-main-menu-pinnable-header vector-pinnable-header-unpinned" data-feature-name="main-menu-pinned" data-pinnable-element-id="vector-main-menu" data-pinned-container-id="vector-main-menu-pinned-container" data-unpinned-container-id="vector-main-menu-unpinned-container" > <div class="vector-pinnable-header-label">Main menu</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-main-menu.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-main-menu.unpin">hide</button> </div> <div id="p-navigation" class="vector-menu mw-portlet mw-portlet-navigation" > <div class="vector-menu-heading"> Navigation </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-mainpage-description" class="mw-list-item"><a href="/wiki/Main_Page" title="Visit the main page [z]" accesskey="z"><span>Main page</span></a></li><li id="n-contents" class="mw-list-item"><a href="/wiki/Wikipedia:Contents" title="Guides to browsing Wikipedia"><span>Contents</span></a></li><li id="n-currentevents" class="mw-list-item"><a href="/wiki/Portal:Current_events" title="Articles related to current events"><span>Current events</span></a></li><li id="n-randompage" class="mw-list-item"><a href="/wiki/Special:Random" title="Visit a randomly selected article [x]" accesskey="x"><span>Random article</span></a></li><li id="n-aboutsite" class="mw-list-item"><a href="/wiki/Wikipedia:About" title="Learn about Wikipedia and how it works"><span>About Wikipedia</span></a></li><li id="n-contactpage" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us" title="How to contact Wikipedia"><span>Contact us</span></a></li> </ul> </div> </div> <div id="p-interaction" class="vector-menu mw-portlet mw-portlet-interaction" > <div class="vector-menu-heading"> Contribute </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-help" class="mw-list-item"><a href="/wiki/Help:Contents" title="Guidance on how to use and edit Wikipedia"><span>Help</span></a></li><li id="n-introduction" class="mw-list-item"><a href="/wiki/Help:Introduction" title="Learn how to edit Wikipedia"><span>Learn to edit</span></a></li><li id="n-portal" class="mw-list-item"><a href="/wiki/Wikipedia:Community_portal" title="The hub for editors"><span>Community portal</span></a></li><li id="n-recentchanges" class="mw-list-item"><a href="/wiki/Special:RecentChanges" title="A list of recent changes to Wikipedia [r]" accesskey="r"><span>Recent changes</span></a></li><li id="n-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_upload_wizard" title="Add images or other media for use on Wikipedia"><span>Upload file</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> <a href="/wiki/Main_Page" class="mw-logo"> <img class="mw-logo-icon" src="/static/images/icons/wikipedia.png" alt="" aria-hidden="true" height="50" width="50"> <span class="mw-logo-container skin-invert"> <img class="mw-logo-wordmark" alt="Wikipedia" src="/static/images/mobile/copyright/wikipedia-wordmark-en.svg" style="width: 7.5em; height: 1.125em;"> <img class="mw-logo-tagline" alt="The Free Encyclopedia" src="/static/images/mobile/copyright/wikipedia-tagline-en.svg" width="117" height="13" style="width: 7.3125em; height: 0.8125em;"> </span> </a> </div> <div class="vector-header-end"> <div id="p-search" role="search" class="vector-search-box-vue vector-search-box-collapses vector-search-box-show-thumbnail vector-search-box-auto-expand-width vector-search-box"> <a href="/wiki/Special:Search" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only search-toggle" title="Search Wikipedia [f]" accesskey="f"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </a> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail cdx-typeahead-search--auto-expand-width"> <form action="/w/index.php" id="searchform" class="cdx-search-input cdx-search-input--has-end-button"> <div id="simpleSearch" class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia" aria-label="Search Wikipedia" autocapitalize="sentences" title="Search Wikipedia [f]" accesskey="f" id="searchInput" > <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <nav class="vector-user-links vector-user-links-wide" aria-label="Personal tools"> <div class="vector-user-links-main"> <div id="p-vector-user-menu-preferences" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-userpage" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-dropdown" class="vector-dropdown " title="Change the appearance of the page's font size, width, and color" > <input type="checkbox" id="vector-appearance-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-appearance-dropdown" class="vector-dropdown-checkbox " aria-label="Appearance" > <label id="vector-appearance-dropdown-label" for="vector-appearance-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-appearance mw-ui-icon-wikimedia-appearance"></span> <span class="vector-dropdown-label-text">Appearance</span> </label> <div class="vector-dropdown-content"> <div id="vector-appearance-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div id="p-vector-user-menu-notifications" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-overflow" class="vector-menu mw-portlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en" class=""><span>Donate</span></a> </li> <li id="pt-createaccount-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:CreateAccount&returnto=Hyperconjugation" title="You are encouraged to create an account and log in; however, it is not mandatory" class=""><span>Create account</span></a> </li> <li id="pt-login-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:UserLogin&returnto=Hyperconjugation" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o" class=""><span>Log in</span></a> </li> </ul> </div> </div> </div> <div id="vector-user-links-dropdown" class="vector-dropdown vector-user-menu vector-button-flush-right vector-user-menu-logged-out" title="Log in and more options" > <input type="checkbox" id="vector-user-links-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-user-links-dropdown" class="vector-dropdown-checkbox " aria-label="Personal tools" > <label id="vector-user-links-dropdown-label" for="vector-user-links-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-ellipsis mw-ui-icon-wikimedia-ellipsis"></span> <span class="vector-dropdown-label-text">Personal tools</span> </label> <div class="vector-dropdown-content"> <div id="p-personal" class="vector-menu mw-portlet mw-portlet-personal user-links-collapsible-item" title="User menu" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport" class="user-links-collapsible-item mw-list-item"><a href="https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en"><span>Donate</span></a></li><li id="pt-createaccount" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:CreateAccount&returnto=Hyperconjugation" title="You are encouraged to create an account and log in; however, it is not mandatory"><span class="vector-icon mw-ui-icon-userAdd mw-ui-icon-wikimedia-userAdd"></span> <span>Create account</span></a></li><li id="pt-login" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:UserLogin&returnto=Hyperconjugation" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o"><span class="vector-icon mw-ui-icon-logIn mw-ui-icon-wikimedia-logIn"></span> <span>Log in</span></a></li> </ul> </div> </div> <div id="p-user-menu-anon-editor" class="vector-menu mw-portlet mw-portlet-user-menu-anon-editor" > <div class="vector-menu-heading"> Pages for logged out editors <a href="/wiki/Help:Introduction" aria-label="Learn more about editing"><span>learn more</span></a> </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-anoncontribs" class="mw-list-item"><a href="/wiki/Special:MyContributions" title="A list of edits made from this IP address [y]" accesskey="y"><span>Contributions</span></a></li><li id="pt-anontalk" class="mw-list-item"><a href="/wiki/Special:MyTalk" title="Discussion about edits from this IP address [n]" accesskey="n"><span>Talk</span></a></li> </ul> </div> </div> </div> </div> </nav> </div> </header> </div> <div class="mw-page-container"> <div class="mw-page-container-inner"> <div class="vector-sitenotice-container"> <div id="siteNotice"></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> <div class="vector-sticky-pinned-container"> <nav id="mw-panel-toc" aria-label="Contents" data-event-name="ui.sidebar-toc" class="mw-table-of-contents-container vector-toc-landmark"> <div id="vector-toc-pinned-container" class="vector-pinned-container"> <div id="vector-toc" class="vector-toc vector-pinnable-element"> <div class="vector-pinnable-header vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">Contents</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Applications" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Applications"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Applications</span> </div> </a> <button aria-controls="toc-Applications-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Applications subsection</span> </button> <ul id="toc-Applications-sublist" class="vector-toc-list"> <li id="toc-Effect_on_chemical_properties" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Effect_on_chemical_properties"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>Effect on chemical properties</span> </div> </a> <ul id="toc-Effect_on_chemical_properties-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Hyperconjugation_in_unsaturated_compounds" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Hyperconjugation_in_unsaturated_compounds"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.2</span> <span>Hyperconjugation in unsaturated compounds</span> </div> </a> <ul id="toc-Hyperconjugation_in_unsaturated_compounds-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Stabilization_of_1,3-butadiyne_and_1,3-butadiene" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Stabilization_of_1,3-butadiyne_and_1,3-butadiene"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.3</span> <span>Stabilization of 1,3-butadiyne and 1,3-butadiene</span> </div> </a> <ul id="toc-Stabilization_of_1,3-butadiyne_and_1,3-butadiene-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Trends_in_hyperconjugation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Trends_in_hyperconjugation"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.4</span> <span>Trends in hyperconjugation</span> </div> </a> <ul id="toc-Trends_in_hyperconjugation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Rotational_barrier_of_ethane" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Rotational_barrier_of_ethane"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.5</span> <span>Rotational barrier of ethane</span> </div> </a> <ul id="toc-Rotational_barrier_of_ethane-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Hyperconjugation</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 20 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-20" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">20 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Hyperkonjugace" title="Hyperkonjugace – Czech" lang="cs" hreflang="cs" data-title="Hyperkonjugace" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Hyperkonjugation" title="Hyperkonjugation – German" lang="de" hreflang="de" data-title="Hyperkonjugation" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Hiperconjugaci%C3%B3n" title="Hiperconjugación – Spanish" lang="es" hreflang="es" data-title="Hiperconjugación" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Hiperkonjugazio" title="Hiperkonjugazio – Basque" lang="eu" hreflang="eu" data-title="Hiperkonjugazio" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Hyperconjugaison" title="Hyperconjugaison – French" lang="fr" hreflang="fr" data-title="Hyperconjugaison" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%B9%E0%A4%BE%E0%A4%87%E0%A4%AA%E0%A4%B0%E0%A4%95%E0%A5%89%E0%A4%A8%E0%A5%8D%E0%A4%9C%E0%A5%81%E0%A4%97%E0%A5%87%E0%A4%B6%E0%A4%A8" title="हाइपरकॉन्जुगेशन – Hindi" lang="hi" hreflang="hi" data-title="हाइपरकॉन्जुगेशन" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Hiperkonjugasi" title="Hiperkonjugasi – Indonesian" lang="id" hreflang="id" data-title="Hiperkonjugasi" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Iperconiugazione" title="Iperconiugazione – Italian" lang="it" hreflang="it" data-title="Iperconiugazione" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%94%D7%99%D7%A4%D7%A8%D7%A7%D7%95%D7%A0%D7%99%D7%95%D7%92%D7%A6%D7%99%D7%94" title="היפרקוניוגציה – Hebrew" lang="he" hreflang="he" data-title="היפרקוניוגציה" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%85%E0%B4%A4%E0%B4%BF%E0%B4%B8%E0%B4%82%E0%B4%AF%E0%B5%81%E0%B4%97%E0%B5%8D%E0%B4%AE%E0%B4%A8%E0%B4%82" title="അതിസംയുഗ്മനം – Malayalam" lang="ml" hreflang="ml" data-title="അതിസംയുഗ്മനം" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Hyperconjugatie" title="Hyperconjugatie – Dutch" lang="nl" hreflang="nl" data-title="Hyperconjugatie" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E8%B6%85%E5%85%B1%E5%BD%B9" title="超共役 – Japanese" lang="ja" hreflang="ja" data-title="超共役" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Hiperconjuga%C3%A7%C3%A3o" title="Hiperconjugação – Portuguese" lang="pt" hreflang="pt" data-title="Hiperconjugação" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Hiperconjugare" title="Hiperconjugare – Romanian" lang="ro" hreflang="ro" data-title="Hiperconjugare" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/Hiperkonjugacija" title="Hiperkonjugacija – Serbian" lang="sr" hreflang="sr" data-title="Hiperkonjugacija" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Hiperkonjugacija" title="Hiperkonjugacija – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Hiperkonjugacija" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Hyperkonjugaatio" title="Hyperkonjugaatio – Finnish" lang="fi" hreflang="fi" data-title="Hyperkonjugaatio" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Hyperkonjugation" title="Hyperkonjugation – Swedish" lang="sv" hreflang="sv" data-title="Hyperkonjugation" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%93%D1%96%D0%BF%D0%B5%D1%80%D0%BA%D0%BE%D0%BD%27%D1%8E%D0%B3%D0%B0%D1%86%D1%96%D1%8F" title="Гіперкон'югація – Ukrainian" lang="uk" hreflang="uk" data-title="Гіперкон'югація" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E8%B6%85%E5%85%B1%E8%BD%AD%E6%95%88%E5%BA%94" title="超共轭效应 – Chinese" lang="zh" hreflang="zh" data-title="超共轭效应" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q899217#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Hyperconjugation" title="View the content page [c]" accesskey="c"><span>Article</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/Talk:Hyperconjugation" rel="discussion" title="Discuss improvements to the content page [t]" accesskey="t"><span>Talk</span></a></li> </ul> </div> </div> <div id="vector-variants-dropdown" class="vector-dropdown emptyPortlet" > <input type="checkbox" id="vector-variants-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-variants-dropdown" class="vector-dropdown-checkbox " aria-label="Change language variant" > <label id="vector-variants-dropdown-label" for="vector-variants-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">English</span> </label> <div class="vector-dropdown-content"> <div id="p-variants" class="vector-menu mw-portlet mw-portlet-variants emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> </div> </div> </nav> </div> <div id="right-navigation" class="vector-collapsible"> <nav aria-label="Views"> <div id="p-views" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-views" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-view" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Hyperconjugation"><span>Read</span></a></li><li id="ca-edit" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Hyperconjugation&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-history" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Hyperconjugation&action=history" title="Past revisions of this page [h]" accesskey="h"><span>View history</span></a></li> </ul> </div> </div> </nav> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-dropdown" class="vector-dropdown vector-page-tools-dropdown" > <input type="checkbox" id="vector-page-tools-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-tools-dropdown" class="vector-dropdown-checkbox " aria-label="Tools" > <label id="vector-page-tools-dropdown-label" for="vector-page-tools-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">Tools</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-tools-unpinned-container" class="vector-unpinned-container"> <div id="vector-page-tools" class="vector-page-tools vector-pinnable-element"> <div class="vector-pinnable-header vector-page-tools-pinnable-header vector-pinnable-header-unpinned" data-feature-name="page-tools-pinned" data-pinnable-element-id="vector-page-tools" data-pinned-container-id="vector-page-tools-pinned-container" data-unpinned-container-id="vector-page-tools-unpinned-container" > <div class="vector-pinnable-header-label">Tools</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-page-tools.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-page-tools.unpin">hide</button> </div> <div id="p-cactions" class="vector-menu mw-portlet mw-portlet-cactions emptyPortlet vector-has-collapsible-items" title="More options" > <div class="vector-menu-heading"> Actions </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-more-view" class="selected vector-more-collapsible-item mw-list-item"><a href="/wiki/Hyperconjugation"><span>Read</span></a></li><li id="ca-more-edit" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Hyperconjugation&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-more-history" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Hyperconjugation&action=history"><span>View history</span></a></li> </ul> </div> </div> <div id="p-tb" class="vector-menu mw-portlet mw-portlet-tb" > <div class="vector-menu-heading"> General </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-whatlinkshere" class="mw-list-item"><a href="/wiki/Special:WhatLinksHere/Hyperconjugation" title="List of all English Wikipedia pages containing links to this page [j]" accesskey="j"><span>What links here</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Special:RecentChangesLinked/Hyperconjugation" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k"><span>Related changes</span></a></li><li id="t-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_Upload_Wizard" title="Upload files [u]" accesskey="u"><span>Upload file</span></a></li><li id="t-specialpages" class="mw-list-item"><a href="/wiki/Special:SpecialPages" title="A list of all special pages [q]" accesskey="q"><span>Special pages</span></a></li><li id="t-permalink" class="mw-list-item"><a href="/w/index.php?title=Hyperconjugation&oldid=1221687648" title="Permanent link to this revision of this page"><span>Permanent link</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=Hyperconjugation&action=info" title="More information about this page"><span>Page information</span></a></li><li id="t-cite" class="mw-list-item"><a href="/w/index.php?title=Special:CiteThisPage&page=Hyperconjugation&id=1221687648&wpFormIdentifier=titleform" title="Information on how to cite this page"><span>Cite this page</span></a></li><li id="t-urlshortener" class="mw-list-item"><a href="/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FHyperconjugation"><span>Get shortened URL</span></a></li><li id="t-urlshortener-qrcode" class="mw-list-item"><a href="/w/index.php?title=Special:QrCode&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FHyperconjugation"><span>Download QR code</span></a></li> </ul> </div> </div> <div id="p-coll-print_export" class="vector-menu mw-portlet mw-portlet-coll-print_export" > <div class="vector-menu-heading"> Print/export </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="coll-download-as-rl" class="mw-list-item"><a href="/w/index.php?title=Special:DownloadAsPdf&page=Hyperconjugation&action=show-download-screen" title="Download this page as a PDF file"><span>Download as PDF</span></a></li><li id="t-print" class="mw-list-item"><a href="/w/index.php?title=Hyperconjugation&printable=yes" title="Printable version of this page [p]" accesskey="p"><span>Printable version</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects" > <div class="vector-menu-heading"> In other projects </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q899217" title="Structured data on this page hosted by Wikidata [g]" accesskey="g"><span>Wikidata item</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Concept in organic chemistry</div> <p>In <a href="/wiki/Organic_chemistry" title="Organic chemistry">organic chemistry</a>, <b>hyperconjugation</b> (<b>σ-conjugation</b> or <b>no-bond <a href="/wiki/Resonance_(chemistry)" title="Resonance (chemistry)">resonance</a></b>) refers to the <a href="/wiki/Delocalization" class="mw-redirect" title="Delocalization">delocalization</a> of <a href="/wiki/Electrons" class="mw-redirect" title="Electrons">electrons</a> with the participation of <a href="/wiki/Chemical_bond" title="Chemical bond">bonds</a> of primarily <a href="/wiki/Sigma_bond" title="Sigma bond">σ-character</a>. Usually, hyperconjugation involves the interaction of the electrons in a sigma (σ) orbital (e.g. C–H or C–C) with an adjacent unpopulated non-bonding p or <a href="/wiki/Antibonding" class="mw-redirect" title="Antibonding">antibonding</a> σ* or <a href="/wiki/Pi_bond" title="Pi bond">π* orbitals</a> to give a pair of extended <a href="/wiki/Molecular_orbital" title="Molecular orbital">molecular orbitals</a>. However, sometimes, low-lying antibonding σ* orbitals may also interact with filled orbitals of lone pair character (n) in what is termed <i><a href="/wiki/Negative_hyperconjugation" title="Negative hyperconjugation">negative hyperconjugation</a></i>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Increased electron delocalization associated with hyperconjugation increases the stability of the system.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> In particular, the new orbital with bonding character is stabilized, resulting in an overall stabilization of the molecule.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Only electrons in bonds that are in the <a href="/wiki/Beta_carbon" class="mw-redirect" title="Beta carbon">β position</a> can have this sort of direct stabilizing effect — donating from a sigma bond on an atom to an orbital in another atom directly attached to it. However, extended versions of hyperconjugation (such as double hyperconjugation<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>) can be important as well. The <a href="/wiki/Baker%E2%80%93Nathan_effect" title="Baker–Nathan effect">Baker–Nathan effect</a>, sometimes used synonymously for hyperconjugation,<sup id="cite_ref-Deasy-CR-1945_6-0" class="reference"><a href="#cite_note-Deasy-CR-1945-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> is a specific application of it to certain chemical reactions or types of structures.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Alkene-hyperconjugation2.png" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/1/11/Alkene-hyperconjugation2.png/200px-Alkene-hyperconjugation2.png" decoding="async" width="200" height="97" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/11/Alkene-hyperconjugation2.png/300px-Alkene-hyperconjugation2.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/11/Alkene-hyperconjugation2.png/400px-Alkene-hyperconjugation2.png 2x" data-file-width="4795" data-file-height="2320" /></a><figcaption>Hyperconjugation: orbital overlap between a σ orbital and π* orbital stabilizes alkyl-substituted alkenes. The σ orbital (solid color) is filled, while the π* orbital (grayed) is an unpopulated antibonding orbital. Ref. Clayden, Greeves, Warren</figcaption></figure> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Applications">Applications</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hyperconjugation&action=edit&section=1" title="Edit section: Applications"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Hyperconjugation can be used to rationalize a variety of chemical phenomena, including the <a href="/wiki/Anomeric_effect" title="Anomeric effect">anomeric effect</a>, the <a href="/wiki/Gauche_effect" title="Gauche effect">gauche effect</a>, the <a href="/wiki/Rotational_barrier" class="mw-redirect" title="Rotational barrier">rotational barrier</a> of <a href="/wiki/Ethane" title="Ethane">ethane</a>, the <a href="/wiki/Beta-silicon_effect" class="mw-redirect" title="Beta-silicon effect">beta-silicon effect</a>, the <a href="/wiki/Vibrational_frequency" class="mw-redirect" title="Vibrational frequency">vibrational frequency</a> of <a href="/wiki/Exocyclic" class="mw-redirect" title="Exocyclic">exocyclic</a> <a href="/wiki/Carbonyl" class="mw-redirect" title="Carbonyl">carbonyl</a> groups, and the relative stability of substituted <a href="/wiki/Carbocation" title="Carbocation">carbocations</a> and substituted carbon centred <a href="/wiki/Radical_(chemistry)" title="Radical (chemistry)">radicals</a>, and the thermodynamic <a href="/wiki/Zaitsev%27s_rule" class="mw-redirect" title="Zaitsev's rule">Zaitsev's rule</a> for alkene stability. More controversially, hyperconjugation is proposed by quantum mechanical modeling to be a better explanation for the preference of the <a href="/wiki/Staggered_conformation" title="Staggered conformation">staggered conformation</a> rather than the old textbook notion of <a href="/wiki/Steric_effects" title="Steric effects">steric hindrance</a>.<sup id="cite_ref-goodman_8-0" class="reference"><a href="#cite_note-goodman-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Effect_on_chemical_properties">Effect on chemical properties</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hyperconjugation&action=edit&section=2" title="Edit section: Effect on chemical properties"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Hyperconjugation affects several properties.<sup id="cite_ref-Deasy-CR-1945_6-1" class="reference"><a href="#cite_note-Deasy-CR-1945-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <ol><li><a href="/wiki/Bond_length" title="Bond length">Bond length</a>: Hyperconjugation is suggested as a key factor in shortening of <a href="/wiki/Sigma_bonds" class="mw-redirect" title="Sigma bonds">sigma bonds</a> (σ bonds). For example, the single C–C bonds in <a href="/wiki/1,3-butadiene" class="mw-redirect" title="1,3-butadiene">1,3-butadiene</a> and <a href="/wiki/Propyne" title="Propyne">propyne</a> are approximately 1.46 Å in length, much less than the value of around 1.54 Å found in saturated <a href="/wiki/Hydrocarbons" class="mw-redirect" title="Hydrocarbons">hydrocarbons</a>. For butadiene, this can be explained as normal conjugation of the two alkenyl parts. But for propyne, it is generally accepted that this is due to hyperconjugation between the alkyl and alkynyl parts.</li> <li><a href="/wiki/Bond_dipole_moment" class="mw-redirect" title="Bond dipole moment">Dipole moments</a>: The large increase in dipole moment of <a href="/wiki/1,1,1-Trichloroethane" title="1,1,1-Trichloroethane">1,1,1-trichloroethane</a> as compared with <a href="/wiki/Chloroform" title="Chloroform">chloroform</a> can be attributed to hyperconjugated structures.</li> <li>The <a href="/wiki/Heat_of_formation" class="mw-redirect" title="Heat of formation">heat of formation</a> of molecules with hyperconjugation are greater than sum of their bond energies and the heats of hydrogenation per double bond are less than the heat of hydrogenation of <a href="/wiki/Ethylene" title="Ethylene">ethylene</a>.</li> <li>Stability of <a href="/wiki/Carbocation" title="Carbocation">carbocations</a>: <dl><dd>(CH<sub>3</sub>)<sub>3</sub>C<sup>+</sup> > (CH<sub>3</sub>)<sub>2</sub>CH<sup>+</sup> > (CH<sub>3</sub>)CH<sub>2</sub><sup>+</sup> > CH<sub>3</sub><sup>+</sup></dd> <dd>The three C–H σ bonds of the methyl group(s) attached to the carbocation can undergo the stabilization interaction but only one of them can be aligned perfectly with the empty p-orbital, depending on the conformation of the carbon–carbon bond. Donation from the two misaligned C–H bonds is weaker.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> The more adjacent methyl groups there are, the larger hyperconjugation stabilization is because of the increased number of adjacent C–H bonds.</dd></dl></li></ol> <div class="mw-heading mw-heading3"><h3 id="Hyperconjugation_in_unsaturated_compounds">Hyperconjugation in unsaturated compounds</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hyperconjugation&action=edit&section=3" title="Edit section: Hyperconjugation in unsaturated compounds"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Hyperconjugation was suggested as the reason for the increased stability of carbon-carbon double bonds as the degree of substitution increases. Early studies in hyperconjugation were performed by in the research group of <a href="/wiki/George_Kistiakowsky" title="George Kistiakowsky">George Kistiakowsky</a>. Their work, first published in 1937, was intended as a preliminary progress report of thermochemical studies of energy changes during <a href="/wiki/Addition_reaction" title="Addition reaction">addition reactions</a> of various <a href="/wiki/Saturated_and_unsaturated_compounds" title="Saturated and unsaturated compounds">unsaturated</a> and cyclic compounds. The importance of hyperconjugation in accounting for this effect has received support from quantum chemical calculations.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> The key interaction is believed to be the donation of electron density from the neighboring C–H σ bond into the π* antibonding orbital of the alkene (σ<sub>C–H</sub>→π*). The effect is almost an order of magnitude weaker than the case of alkyl substitution on carbocations (σ<sub>C–H</sub>→p<sub>C</sub>), since an unfilled p orbital is lower in energy, and, therefore, better energetically matched to a σ bond. When this effect manifests in the formation of the more substituted product in thermodynamically controlled E1 reactions, it is known as <a href="/wiki/Zaitsev%27s_rule" class="mw-redirect" title="Zaitsev's rule">Zaitsev's rule</a>, although in many cases the kinetic product also follows this rule. (<i>See <a href="/wiki/Hofmann%27s_Rule" class="mw-redirect" title="Hofmann's Rule">Hofmann's rule</a> for cases where the kinetic product is the less substituted one.</i>) </p><p>One set of experiments by Kistiakowsky involved collected heats of <a href="/wiki/Hydrogenation" title="Hydrogenation">hydrogenation</a> data during gas-phase reactions of a range of compounds that contained one <a href="/wiki/Alkene" title="Alkene">alkene</a> unit. When comparing a range of mono<a href="/wiki/Alkyl" class="mw-redirect" title="Alkyl">alkyl</a>-substituted alkenes, they found any alkyl group noticeably increased the stability, but that the choice of different specific alkyl groups had little to no effect.<sup id="cite_ref-Kistiakowsky_13-0" class="reference"><a href="#cite_note-Kistiakowsky-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p>A portion of Kistiakowsky's work involved a comparison of other unsaturated compounds in the form of CH<sub>2</sub>=CH(CH<sub>2</sub>)n-CH=CH<sub>2</sub> (n=0,1,2). These experiments revealed an important result; when n=0, there is an effect of conjugation to the molecule where the ΔH value is lowered by 3.5 <a href="/wiki/Kcal" class="mw-redirect" title="Kcal">kcal</a>. This is likened to the addition of two alkyl groups into ethylene. Kistiakowsky also investigated open chain systems, where the largest value of heat liberated was found to be during the addition to a molecule in the 1,4-position. Cyclic molecules proved to be the most problematic, as it was found that the <a href="/wiki/Strain_energy" title="Strain energy">strain</a> of the molecule would have to be considered. The strain of five-membered rings increased with a decrease degree of unsaturation. This was a surprising result that was further investigated in later work with cyclic <a href="/wiki/Acid_anhydride" title="Acid anhydride">acid anhydrides</a> and <a href="/wiki/Lactone" title="Lactone">lactones</a>. Cyclic molecules like <a href="/wiki/Benzene" title="Benzene">benzene</a> and its derivatives were also studied, as their behaviors were different from other unsaturated compounds.<sup id="cite_ref-Kistiakowsky_13-1" class="reference"><a href="#cite_note-Kistiakowsky-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p>Despite the thoroughness of Kistiakowsky's work, it was not complete and needed further evidence to back up his findings. His work was a crucial first step to the beginnings of the ideas of hyperconjugation and conjugation effects. </p> <div class="mw-heading mw-heading3"><h3 id="Stabilization_of_1,3-butadiyne_and_1,3-butadiene"><span id="Stabilization_of_1.2C3-butadiyne_and_1.2C3-butadiene"></span>Stabilization of 1,3-butadiyne and 1,3-butadiene</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hyperconjugation&action=edit&section=4" title="Edit section: Stabilization of 1,3-butadiyne and 1,3-butadiene"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Conjugated_system" title="Conjugated system">conjugation</a> of 1,3-<a href="/wiki/Butadiene" title="Butadiene">butadiene</a> was first evaluated by Kistiakowsky, a conjugative contribution of 3.5 <a href="/wiki/Kcal/mol" class="mw-redirect" title="Kcal/mol">kcal/mol</a> was found based on the energetic comparison of <a href="/wiki/Hydrogenation" title="Hydrogenation">hydrogenation</a> between conjugated species and unconjugated analogues.<sup id="cite_ref-Kistiakowsky_13-2" class="reference"><a href="#cite_note-Kistiakowsky-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> Rogers who used the method first applied by Kistiakowsky, reported that the conjugation stabilization of <a href="/wiki/1,3-butadiyne" class="mw-redirect" title="1,3-butadiyne">1,3-butadiyne</a> was zero, as the difference of Δ<sub>hyd</sub>H between first and second hydrogenation was zero. The heats of hydrogenation (Δ<sub>hyd</sub>H) were obtained by computational G3(MP2) quantum chemistry method.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <dl><dd><span typeof="mw:File"><a href="/wiki/File:Rogers%27s_zero_conjugation_stabilization_of_1,3-butadiyne.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/88/Rogers%27s_zero_conjugation_stabilization_of_1%2C3-butadiyne.png/540px-Rogers%27s_zero_conjugation_stabilization_of_1%2C3-butadiyne.png" decoding="async" width="540" height="45" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/88/Rogers%27s_zero_conjugation_stabilization_of_1%2C3-butadiyne.png/810px-Rogers%27s_zero_conjugation_stabilization_of_1%2C3-butadiyne.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/88/Rogers%27s_zero_conjugation_stabilization_of_1%2C3-butadiyne.png/1080px-Rogers%27s_zero_conjugation_stabilization_of_1%2C3-butadiyne.png 2x" data-file-width="1693" data-file-height="141" /></a></span></dd></dl> <p>Another group led by Houk<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> suggested the methods employed by Rogers and Kistiakowsky was inappropriate, because that comparisons of heats of hydrogenation evaluate not only conjugation effects but also other structural and electronic differences. They obtained -70.6 kcal/mol and -70.4 kcal/mol for the first and second hydrogenation respectively by <a href="/wiki/Ab_initio" title="Ab initio">ab initio</a> calculation, which confirmed Rogers’ data. However, they interpreted the data differently by taking into account the hyperconjugation stabilization. To quantify hyperconjugation effect, they designed the following <a href="/wiki/Isodesmic_reaction" title="Isodesmic reaction">isodesmic reactions</a> in <a href="/wiki/1-butyne" class="mw-redirect" title="1-butyne">1-butyne</a> and <a href="/wiki/1-butene" class="mw-redirect" title="1-butene">1-butene</a>. </p> <dl><dd><span typeof="mw:File"><a href="/wiki/File:Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/da/Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png/540px-Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png" decoding="async" width="540" height="169" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/da/Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png/810px-Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/da/Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png/1080px-Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png 2x" data-file-width="1471" data-file-height="460" /></a></span></dd></dl> <p>Deleting the hyperconjugative interactions gives virtual states that have energies that are 4.9 and 2.4 kcal/mol higher than those of <a href="/wiki/1-butyne" class="mw-redirect" title="1-butyne">1-butyne</a> and <a href="/wiki/1-butene" class="mw-redirect" title="1-butene">1-butene</a>, respectively. Employment of these virtual states results in a 9.6 kcal/mol conjugative stabilization for 1,3-butadiyne and 8.5 kcal/mol for 1,3-butadiene. </p> <dl><dd><span typeof="mw:File"><a href="/wiki/File:Virtual_states_in_Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/90/Virtual_states_in_Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png/540px-Virtual_states_in_Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png" decoding="async" width="540" height="159" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/90/Virtual_states_in_Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png/810px-Virtual_states_in_Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/90/Virtual_states_in_Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png/1080px-Virtual_states_in_Houk_%26_Schleyer%27s_diyne_conjugative_stabilization.png 2x" data-file-width="1711" data-file-height="503" /></a></span></dd></dl> <div class="mw-heading mw-heading3"><h3 id="Trends_in_hyperconjugation">Trends in hyperconjugation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hyperconjugation&action=edit&section=5" title="Edit section: Trends in hyperconjugation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A relatively recent work (2006) by Fernández and Frenking (2006) summarized the trends in hyperconjugation among various groups of acyclic molecules, using energy decomposition analysis or EDA. Fernández and Frenking define this type of analysis as "...a method that uses only the pi orbitals of the interacting fragments in the geometry of the molecule for estimating pi interactions.<sup id="cite_ref-Frenking_16-0" class="reference"><a href="#cite_note-Frenking-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup>" For this type of analysis, the formation of bonds between various molecular moieties is a combination of three component terms. ΔE<sub>elstat</sub> represents what Fernández and Frenking call a molecule's “quasiclassical electrostatic attractions.<sup id="cite_ref-Frenking_16-1" class="reference"><a href="#cite_note-Frenking-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup>” The second term, ΔE<sub>Pauli</sub>, represents the molecule's Pauli repulsion. ΔE<sub>orb</sub>, the third term, represents stabilizing interactions between orbitals, and is defined as the sum of ΔE<sub>pi</sub> and ΔE<sub>sigma</sub>. The total energy of interaction, ΔE<sub>int</sub>, is the result of the sum of the 3 terms.<sup id="cite_ref-Frenking_16-2" class="reference"><a href="#cite_note-Frenking-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </p><p> A group whose ΔE<sub>pi</sub> values were very thoroughly analyzed were a group of <a href="/wiki/Enone" class="mw-redirect" title="Enone">enones</a> that varied in substituent. </p><figure class="mw-halign-center" typeof="mw:File"><a href="/wiki/File:Enone.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/23/Enone.svg/260px-Enone.svg.png" decoding="async" width="260" height="100" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/23/Enone.svg/390px-Enone.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/23/Enone.svg/520px-Enone.svg.png 2x" data-file-width="725" data-file-height="280" /></a><figcaption></figcaption></figure> <p>Fernández and Frenking reported that the <a href="/wiki/Methyl" class="mw-redirect" title="Methyl">methyl</a>, <a href="/wiki/Hydroxyl" class="mw-redirect" title="Hydroxyl">hydroxyl</a>, and <a href="/wiki/Amino" class="mw-redirect" title="Amino">amino</a> substituents resulted in a decrease in ΔE<sub>pi</sub> from the parent <a href="/wiki/2-propenal" class="mw-redirect" title="2-propenal">2-propenal</a>. Conversely, <a href="/wiki/Halide" title="Halide">halide</a> substituents of increasing atomic mass resulted in increasing ΔE<sub>pi</sub>. Because both the enone study and <a href="/wiki/Hammett_equation" title="Hammett equation">Hammett</a> analysis study substituent effects (although in different species), Fernández and Frenking felt that comparing the two to investigate possible trends might yield significant insight into their own results. They observed a linear relationship between the ΔE<sub>pi</sub> values for the substituted enones and the corresponding Hammett constants. The slope of the graph was found to be -51.67, with a correlation coefficient of -0.97 and a standard deviation of 0.54.<sup id="cite_ref-Frenking_16-3" class="reference"><a href="#cite_note-Frenking-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> Fernández and Frenking conclude from this data that ..."the electronic effects of the substituents R on pi conjugation in homo- and heteroconjugated systems is similar and thus appears to be rather independent of the nature of the conjugating system.".<sup id="cite_ref-Frenking_16-4" class="reference"><a href="#cite_note-Frenking-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Rotational_barrier_of_ethane">Rotational barrier of ethane</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hyperconjugation&action=edit&section=6" title="Edit section: Rotational barrier of ethane"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>An instance where hyperconjugation may be overlooked as a possible chemical explanation is in rationalizing the <a href="/wiki/Rotational_barrier" class="mw-redirect" title="Rotational barrier">rotational barrier</a> of ethane (C<sub>2</sub>H<sub>6</sub>). It had been accepted as early as the 1930s that the <a href="/wiki/Staggered_conformation" title="Staggered conformation">staggered conformations</a> of ethane were more stable than the <a href="/wiki/Eclipsed_conformation" title="Eclipsed conformation">eclipsed conformation</a>. Wilson had proven that the <a href="/wiki/Activation_energy" title="Activation energy">energy barrier</a> between any pair of eclipsed and staggered conformations is approximately 3 kcal/mol, and the generally accepted rationale for this was the unfavorable <a href="/wiki/Steric_hindrance" class="mw-redirect" title="Steric hindrance">steric interactions</a> between hydrogen atoms. </p> <figure class="mw-halign-center" typeof="mw:File/Thumb"><a href="/wiki/File:Staggered_and_eclipsed.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Staggered_and_eclipsed.svg/300px-Staggered_and_eclipsed.svg.png" decoding="async" width="300" height="146" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Staggered_and_eclipsed.svg/450px-Staggered_and_eclipsed.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/2d/Staggered_and_eclipsed.svg/600px-Staggered_and_eclipsed.svg.png 2x" data-file-width="338" data-file-height="164" /></a><figcaption>Newman's Projections:Staggered (left) and eclipsed (right)</figcaption></figure> <p>In their 2001 paper, however, Pophristic and Goodman<sup id="cite_ref-goodman_8-1" class="reference"><a href="#cite_note-goodman-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> revealed that this explanation may be too simplistic.<sup id="cite_ref-Schreiner_18-0" class="reference"><a href="#cite_note-Schreiner-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> Goodman focused on three principal physical factors: hyperconjugative interactions, exchange repulsion defined by the <a href="/wiki/Pauli_exclusion_principle" title="Pauli exclusion principle">Pauli exclusion principle</a>, and electrostatic interactions (<a href="/wiki/Coulomb_repulsion" class="mw-redirect" title="Coulomb repulsion">Coulomb interactions</a>). By comparing a traditional ethane molecule and a hypothetical ethane molecule with all exchange repulsions removed, potential curves were prepared by plotting <a href="/wiki/Torsional_angle" class="mw-redirect" title="Torsional angle">torsional angle</a> versus energy for each molecule. The analysis of the curves determined that the staggered conformation had no connection to the amount of electrostatic repulsions within the molecule. These results demonstrate that Coulombic forces do not explain the favored staggered conformations, despite the fact that central bond stretching decreases electrostatic interactions.<sup id="cite_ref-goodman_8-2" class="reference"><a href="#cite_note-goodman-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>Goodman also conducted studies to determine the contribution of <a href="/wiki/Vicinal_(chemistry)" title="Vicinal (chemistry)">vicinal</a> (between two methyl groups) vs. geminal (between the atoms in a single methyl group) interactions to hyperconjugation. In separate experiments, the geminal and vicinal interactions were removed, and the most stable conformer for each interaction was deduced.<sup id="cite_ref-goodman_8-3" class="reference"><a href="#cite_note-goodman-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p> <table class="wikitable" style="text-align:center"> <caption>Calculated torsional angle of ethane with deleted hyperconjugative effects </caption> <tbody><tr> <th>Deleted interaction</th> <th>Torsional angle</th> <th>Corresponding conformer </th></tr> <tr> <td>None</td> <td>60°</td> <td>Staggered </td></tr> <tr> <td>All hyperconjugation</td> <td>0°</td> <td>Eclipsed </td></tr> <tr> <td>Vicinal hyperconjugation</td> <td>0°</td> <td>Eclipsed </td></tr> <tr> <td>Geminal hyperconjugation</td> <td>60°</td> <td>Staggered </td></tr> </tbody></table> <p>From these experiments, it can be concluded that hyperconjugative effects delocalize charge and stabilize the molecule. Further, it is the vicinal hyperconjugative effects that keep the molecule in the staggered conformation.<sup id="cite_ref-goodman_8-4" class="reference"><a href="#cite_note-goodman-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> Thanks to this work, the following model of the stabilization of the staggered conformation of ethane is now more accepted: </p> <figure class="mw-halign-center" typeof="mw:File"><a href="/wiki/File:Schreiner_hyperconjugation.svg" class="mw-file-description" title="Based on a figure in Schreiner (2002)"><img alt="Based on a figure in Schreiner (2002)" src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Schreiner_hyperconjugation.svg/470px-Schreiner_hyperconjugation.svg.png" decoding="async" width="470" height="106" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Schreiner_hyperconjugation.svg/705px-Schreiner_hyperconjugation.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Schreiner_hyperconjugation.svg/940px-Schreiner_hyperconjugation.svg.png 2x" data-file-width="491" data-file-height="111" /></a><figcaption>Based on a figure in Schreiner (2002)</figcaption></figure> <p>Hyperconjugation can also explain several other phenomena whose explanations may also not be as intuitive as that for the rotational barrier of ethane.<sup id="cite_ref-Schreiner_18-1" class="reference"><a href="#cite_note-Schreiner-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p><p>The matter of the rotational barrier of ethane is not settled within the scientific community. An analysis within quantitative <a href="/wiki/Molecular_orbital_theory" title="Molecular orbital theory">molecular orbital theory</a> shows that 2-orbital-4-electron (steric) repulsions are dominant over hyperconjugation.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> A <a href="/wiki/Valence_bond_theory" title="Valence bond theory">valence bond theory</a> study also emphasizes the importance of steric effects.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hyperconjugation&action=edit&section=7" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Conjugated_system" title="Conjugated system">Conjugated system</a></li> <li><a href="/wiki/Negative_hyperconjugation" title="Negative hyperconjugation">Negative hyperconjugation</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hyperconjugation&action=edit&section=8" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><a href="/wiki/International_Union_of_Pure_and_Applied_Chemistry" title="International Union of Pure and Applied Chemistry">IUPAC</a>, <i><a href="/wiki/IUPAC_books#Gold_Book" class="mw-redirect" title="IUPAC books">Compendium of Chemical Terminology</a></i>, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "<a rel="nofollow" class="external text" href="https://goldbook.iupac.org/terms/view/H02924.html">hyperconjugation</a>". <style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1351%2Fgoldbook.H02924">10.1351/goldbook.H02924</a></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text">John McMurry. <i>Organic chemistry</i>, 2nd edition. <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-534-07968-7" title="Special:BookSources/0-534-07968-7">0-534-07968-7</a></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAlabuginGilmorePeterson2011" class="citation journal cs1">Alabugin, I.V.; Gilmore, K.; Peterson, P. (2011). "Hyperconjugation". <i>WIREs Comput Mol Sci</i>. <b>1</b>: 109–141. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2Fwcms.6">10.1002/wcms.6</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:222197582">222197582</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=WIREs+Comput+Mol+Sci&rft.atitle=Hyperconjugation&rft.volume=1&rft.pages=109-141&rft.date=2011&rft_id=info%3Adoi%2F10.1002%2Fwcms.6&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A222197582%23id-name%3DS2CID&rft.aulast=Alabugin&rft.aufirst=I.V.&rft.au=Gilmore%2C+K.&rft.au=Peterson%2C+P.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text">The mixed orbital of antibonding character is, in fact, raised in energy compared to the original antibonding orbital. However, since the antibonding orbital remains unpopulated in most cases, this does not usually affect the energy of the system.</span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text">Alabugin, I. V. (2016) Remote Stereoelectronic Effects, in Stereoelectronic Effects: A Bridge Between Structure and Reactivity, John Wiley & Sons, Ltd, Chichester, UK. <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2F9781118906378.ch8">10.1002/9781118906378.ch8</a></span> </li> <li id="cite_note-Deasy-CR-1945-6"><span class="mw-cite-backlink">^ <a href="#cite_ref-Deasy-CR-1945_6-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Deasy-CR-1945_6-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDeasy1945" class="citation journal cs1">Deasy, C.L. (1945). "Hyperconjugation". <i><a href="/wiki/Chem._Rev." class="mw-redirect" title="Chem. Rev.">Chem. Rev.</a></i> <b>36</b> (2): 145–155. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fcr60114a001">10.1021/cr60114a001</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Chem.+Rev.&rft.atitle=Hyperconjugation&rft.volume=36&rft.issue=2&rft.pages=145-155&rft.date=1945&rft_id=info%3Adoi%2F10.1021%2Fcr60114a001&rft.aulast=Deasy&rft.aufirst=C.L.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMadan2013" class="citation book cs1">Madan, R.L. (2013). "4.14: Hyperconjugation or No-bond Resonance". <i>Organic Chemistry</i>. Tata McGraw–Hill. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9789332901070" title="Special:BookSources/9789332901070"><bdi>9789332901070</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=4.14%3A+Hyperconjugation+or+No-bond+Resonance&rft.btitle=Organic+Chemistry&rft.pub=Tata+McGraw%E2%80%93Hill&rft.date=2013&rft.isbn=9789332901070&rft.aulast=Madan&rft.aufirst=R.L.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-goodman-8"><span class="mw-cite-backlink">^ <a href="#cite_ref-goodman_8-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-goodman_8-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-goodman_8-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-goodman_8-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-goodman_8-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPophristicGoodman2001" class="citation journal cs1">Pophristic, V.; Goodman, L. (2001). "Hyperconjugation not steric repulsion leads to the staggered structure of ethane". <i><a href="/wiki/Nature_(journal)" title="Nature (journal)">Nature</a></i>. <b>411</b> (6837): 565–8. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2001Natur.411..565P">2001Natur.411..565P</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F35079036">10.1038/35079036</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/11385566">11385566</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:205017635">205017635</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=Hyperconjugation+not+steric+repulsion+leads+to+the+staggered+structure+of+ethane.&rft.volume=411&rft.issue=6837&rft.pages=565-8&rft.date=2001&rft_id=info%3Adoi%2F10.1038%2F35079036&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A205017635%23id-name%3DS2CID&rft_id=info%3Apmid%2F11385566&rft_id=info%3Abibcode%2F2001Natur.411..565P&rft.aulast=Pophristic&rft.aufirst=V.&rft.au=Goodman%2C+L.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWeinhold2001" class="citation journal cs1">Weinhold, Frank (2001). "Chemistry. A new twist on molecular shape". <i><a href="/wiki/Nature_(journal)" title="Nature (journal)">Nature</a></i>. <b>411</b> (6837): 539–41. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2001Natur.411..539W">2001Natur.411..539W</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F35079225">10.1038/35079225</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/11385553">11385553</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:9812878">9812878</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=Chemistry.+A+new+twist+on+molecular+shape.&rft.volume=411&rft.issue=6837&rft.pages=539-41&rft.date=2001&rft_id=info%3Adoi%2F10.1038%2F35079225&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A9812878%23id-name%3DS2CID&rft_id=info%3Apmid%2F11385553&rft_id=info%3Abibcode%2F2001Natur.411..539W&rft.aulast=Weinhold&rft.aufirst=Frank&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSchmeising1959" class="citation journal cs1">Schmeising, H.N.; et al. (1959). "A Re-Evaluation of Conjugation and Hyperconjugation: The Effects of Changes in Hybridisation on Carbon Bonds". <i><a href="/wiki/Tetrahedron_(journal)" title="Tetrahedron (journal)">Tetrahedron</a></i>. <b>5</b> (2–3): 166–178. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2F0040-4020%2859%2980102-2">10.1016/0040-4020(59)80102-2</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Tetrahedron&rft.atitle=A+Re-Evaluation+of+Conjugation+and+Hyperconjugation%3A+The+Effects+of+Changes+in+Hybridisation+on+Carbon+Bonds&rft.volume=5&rft.issue=2%E2%80%933&rft.pages=166-178&rft.date=1959&rft_id=info%3Adoi%2F10.1016%2F0040-4020%2859%2980102-2&rft.aulast=Schmeising&rft.aufirst=H.N.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAlabuginBreschdos_Passos_Gomes2014" class="citation journal cs1">Alabugin, Igor V.; Bresch, Stefan; dos Passos Gomes, Gabriel (2014). "Orbital hybridization: a key electronic factor in control of structure and reactivity". <i>Journal of Physical Organic Chemistry</i>. <b>28</b> (2): 147–162. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2Fpoc.3382">10.1002/poc.3382</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Physical+Organic+Chemistry&rft.atitle=Orbital+hybridization%3A+a+key+electronic+factor+in+control+of+structure+and+reactivity&rft.volume=28&rft.issue=2&rft.pages=147-162&rft.date=2014&rft_id=info%3Adoi%2F10.1002%2Fpoc.3382&rft.aulast=Alabugin&rft.aufirst=Igor+V.&rft.au=Bresch%2C+Stefan&rft.au=dos+Passos+Gomes%2C+Gabriel&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBraidaPranaHiberty2009" class="citation journal cs1">Braida, Benoit; Prana, Vinca; Hiberty, Philippe C. (2009). "The Physical Origin of Saytzeff's Rule". <i>Angewandte Chemie International Edition</i>. <b>48</b> (31): 5724–5728. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2Fanie.200901923">10.1002/anie.200901923</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1521-3773">1521-3773</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/19562814">19562814</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Angewandte+Chemie+International+Edition&rft.atitle=The+Physical+Origin+of+Saytzeff%27s+Rule&rft.volume=48&rft.issue=31&rft.pages=5724-5728&rft.date=2009&rft.issn=1521-3773&rft_id=info%3Apmid%2F19562814&rft_id=info%3Adoi%2F10.1002%2Fanie.200901923&rft.aulast=Braida&rft.aufirst=Benoit&rft.au=Prana%2C+Vinca&rft.au=Hiberty%2C+Philippe+C.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-Kistiakowsky-13"><span class="mw-cite-backlink">^ <a href="#cite_ref-Kistiakowsky_13-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Kistiakowsky_13-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Kistiakowsky_13-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKistiakowsky1937" class="citation journal cs1">Kistiakowsky, G. B.; et al. (1937). "Energy Changes Involved in the Addition Reactions of Unsaturated Hydrocarbons". <i><a href="/wiki/Chem._Rev." class="mw-redirect" title="Chem. Rev.">Chem. Rev.</a></i> <b>20</b> (2): 181–194. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fcr60066a002">10.1021/cr60066a002</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Chem.+Rev.&rft.atitle=Energy+Changes+Involved+in+the+Addition+Reactions+of+Unsaturated+Hydrocarbons&rft.volume=20&rft.issue=2&rft.pages=181-194&rft.date=1937&rft_id=info%3Adoi%2F10.1021%2Fcr60066a002&rft.aulast=Kistiakowsky&rft.aufirst=G.+B.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFRogers2003" class="citation journal cs1">Rogers, D. W.; et al. (2003). "The Conjugation Stabilization of 1,3-Butadiyne is Zero". <i><a href="/wiki/Org._Lett." class="mw-redirect" title="Org. Lett.">Org. Lett.</a></i> <b>5</b> (14): 2373–5. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fol030019h">10.1021/ol030019h</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/12841733">12841733</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Org.+Lett.&rft.atitle=The+Conjugation+Stabilization+of+1%2C3-Butadiyne+is+Zero&rft.volume=5&rft.issue=14&rft.pages=2373-5&rft.date=2003&rft_id=info%3Adoi%2F10.1021%2Fol030019h&rft_id=info%3Apmid%2F12841733&rft.aulast=Rogers&rft.aufirst=D.+W.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFHouk2004" class="citation journal cs1">Houk, K.N.; et al. (2004). "How Large is the Conjugative Stabilization of Diynes?". <i><a href="/wiki/J._Am._Chem._Soc." class="mw-redirect" title="J. Am. Chem. Soc.">J. Am. Chem. Soc.</a></i> <b>126</b> (46): 15036–7. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fja046432h">10.1021/ja046432h</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/15547994">15547994</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=J.+Am.+Chem.+Soc.&rft.atitle=How+Large+is+the+Conjugative+Stabilization+of+Diynes%3F&rft.volume=126&rft.issue=46&rft.pages=15036-7&rft.date=2004&rft_id=info%3Adoi%2F10.1021%2Fja046432h&rft_id=info%3Apmid%2F15547994&rft.aulast=Houk&rft.aufirst=K.N.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-Frenking-16"><span class="mw-cite-backlink">^ <a href="#cite_ref-Frenking_16-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Frenking_16-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Frenking_16-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Frenking_16-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Frenking_16-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFernandezFrenking2006" class="citation journal cs1">Fernandez, I.; Frenking, G. (2006). "Direct Estimate of the Strength of Conjugation and Hyperconjugation by the Energy Decomposition Analysis Method". <i><a href="/wiki/Chem._Eur._J." class="mw-redirect" title="Chem. Eur. J.">Chem. Eur. J.</a></i> <b>12</b> (13): 3617–29. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2Fchem.200501405">10.1002/chem.200501405</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/16502455">16502455</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Chem.+Eur.+J.&rft.atitle=Direct+Estimate+of+the+Strength+of+Conjugation+and+Hyperconjugation+by+the+Energy+Decomposition+Analysis+Method&rft.volume=12&rft.issue=13&rft.pages=3617-29&rft.date=2006&rft_id=info%3Adoi%2F10.1002%2Fchem.200501405&rft_id=info%3Apmid%2F16502455&rft.aulast=Fernandez&rft.aufirst=I.&rft.au=Frenking%2C+G.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text">Refer to Reference 12 for the graph and its full analysis</span> </li> <li id="cite_note-Schreiner-18"><span class="mw-cite-backlink">^ <a href="#cite_ref-Schreiner_18-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Schreiner_18-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSchreiner2002" class="citation journal cs1">Schreiner, P. (2002). "Teaching the Right Reasons: Lessons from the Mistaken Origin of the Rotational Barrier in Ethane". <i><a href="/wiki/Angew._Chem._Int._Ed." class="mw-redirect" title="Angew. Chem. Int. Ed.">Angew. Chem. Int. Ed.</a></i> <b>41</b> (19): 3579–81, 3513. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2F1521-3773%2820021004%2941%3A19%3C3579%3A%3AAID-ANIE3579%3E3.0.CO%3B2-S">10.1002/1521-3773(20021004)41:19<3579::AID-ANIE3579>3.0.CO;2-S</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/12370897">12370897</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Angew.+Chem.+Int.+Ed.&rft.atitle=Teaching+the+Right+Reasons%3A+Lessons+from+the+Mistaken+Origin+of+the+Rotational+Barrier+in+Ethane&rft.volume=41&rft.issue=19&rft.pages=3579-81%2C+3513&rft.date=2002&rft_id=info%3Adoi%2F10.1002%2F1521-3773%2820021004%2941%3A19%3C3579%3A%3AAID-ANIE3579%3E3.0.CO%3B2-S&rft_id=info%3Apmid%2F12370897&rft.aulast=Schreiner&rft.aufirst=P.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBickelhauptBaerends2003" class="citation journal cs1">Bickelhaupt, F.M.; Baerends (2003). "The case for steric repulsion causing the staggered conformation of ethane". <i>Angew. Chem. Int. Ed</i>. <b>42</b> (35): 4183–4188. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2Fanie.200350947">10.1002/anie.200350947</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/14502731">14502731</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Angew.+Chem.+Int.+Ed.&rft.atitle=The+case+for+steric+repulsion+causing+the+staggered+conformation+of+ethane.&rft.volume=42&rft.issue=35&rft.pages=4183-4188&rft.date=2003&rft_id=info%3Adoi%2F10.1002%2Fanie.200350947&rft_id=info%3Apmid%2F14502731&rft.aulast=Bickelhaupt&rft.aufirst=F.M.&rft.au=Baerends&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMo2004" class="citation journal cs1">Mo, Y.R.; et al. (2004). "The magnitude of hyperconjugation in ethane: A perspective from ab initio valence bond theory". <i>Angew. Chem. Int. Ed</i>. <b>43</b> (15): 1986–1990. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2Fanie.200352931">10.1002/anie.200352931</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/15065281">15065281</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Angew.+Chem.+Int.+Ed.&rft.atitle=The+magnitude+of+hyperconjugation+in+ethane%3A+A+perspective+from+ab+initio+valence+bond+theory&rft.volume=43&rft.issue=15&rft.pages=1986-1990&rft.date=2004&rft_id=info%3Adoi%2F10.1002%2Fanie.200352931&rft_id=info%3Apmid%2F15065281&rft.aulast=Mo&rft.aufirst=Y.R.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AHyperconjugation" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Hyperconjugation&action=edit&section=9" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20151025181644/https://www.princeton.edu/chemistry/macmillan/group-meetings/hyperconjugation.pdf">Advanced hyperconjugation</a></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · ";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output .hlist dt:last-child::after,.mw-parser-output .hlist li:last-child::after{content:none}.mw-parser-output .hlist dd dd:first-child::before,.mw-parser-output .hlist dd dt:first-child::before,.mw-parser-output .hlist dd li:first-child::before,.mw-parser-output .hlist dt dd:first-child::before,.mw-parser-output .hlist dt dt:first-child::before,.mw-parser-output .hlist dt li:first-child::before,.mw-parser-output .hlist li dd:first-child::before,.mw-parser-output .hlist li dt:first-child::before,.mw-parser-output .hlist li li:first-child::before{content:" (";font-weight:normal}.mw-parser-output .hlist dd dd:last-child::after,.mw-parser-output .hlist dd dt:last-child::after,.mw-parser-output .hlist dd li:last-child::after,.mw-parser-output .hlist dt dd:last-child::after,.mw-parser-output .hlist dt dt:last-child::after,.mw-parser-output .hlist dt li:last-child::after,.mw-parser-output .hlist li dd:last-child::after,.mw-parser-output .hlist li dt:last-child::after,.mw-parser-output .hlist li li:last-child::after{content:")";font-weight:normal}.mw-parser-output .hlist ol{counter-reset:listitem}.mw-parser-output .hlist ol>li{counter-increment:listitem}.mw-parser-output .hlist ol>li::before{content:" "counter(listitem)"\a0 "}.mw-parser-output .hlist dd ol>li:first-child::before,.mw-parser-output .hlist dt ol>li:first-child::before,.mw-parser-output .hlist li ol>li:first-child::before{content:" ("counter(listitem)"\a0 "}</style><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output .navbox-group{white-space:nowrap;text-align:right}.mw-parser-output .navbox,.mw-parser-output .navbox-subgroup{background-color:#fdfdfd}.mw-parser-output .navbox-list{line-height:1.5em;border-color:#fdfdfd}.mw-parser-output .navbox-list-with-group{text-align:left;border-left-width:2px;border-left-style:solid}.mw-parser-output tr+tr>.navbox-abovebelow,.mw-parser-output tr+tr>.navbox-group,.mw-parser-output tr+tr>.navbox-image,.mw-parser-output tr+tr>.navbox-list{border-top:2px solid #fdfdfd}.mw-parser-output .navbox-title{background-color:#ccf}.mw-parser-output .navbox-abovebelow,.mw-parser-output .navbox-group,.mw-parser-output .navbox-subgroup .navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Chemical_bonds" style="padding:3px"><table class="nowraplinks mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="3"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Chemical_bonds" title="Template:Chemical bonds"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Chemical_bonds" title="Template talk:Chemical bonds"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Chemical_bonds" title="Special:EditPage/Template:Chemical bonds"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Chemical_bonds" style="font-size:114%;margin:0 4em"><a href="/wiki/Chemical_bond" title="Chemical bond">Chemical bonds</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Intramolecular_force" title="Intramolecular force">Intramolecular</a><br />(strong)</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Covalent_bond" title="Covalent bond">Covalent</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Electron_deficiency" title="Electron deficiency">Electron deficiency</a> <ul><li><a href="/wiki/Three-center_two-electron_bond" title="Three-center two-electron bond">3c–2e</a></li> <li><a href="/wiki/Four-center_two-electron_bond" title="Four-center two-electron bond">4c–2e</a></li> <li><a href="/wiki/Eight-center_two-electron_bond" class="mw-redirect" title="Eight-center two-electron bond">8c–2e</a></li></ul></li> <li><a href="/wiki/Hypervalent_molecule" title="Hypervalent molecule">Hypervalence</a> <ul><li><a href="/wiki/Three-center_four-electron_bond" title="Three-center four-electron bond">3c–4e</a></li></ul></li> <li><a href="/wiki/Agostic_interaction" title="Agostic interaction">Agostic</a></li> <li><a href="/wiki/Bent_bond" title="Bent bond">Bent</a></li> <li><a href="/wiki/Coordinate_covalent_bond" title="Coordinate covalent bond">Coordinate (dipolar)</a></li> <li><a href="/wiki/Pi_backbonding" title="Pi backbonding">Pi backbond</a></li> <li><a href="/wiki/Metal%E2%80%93ligand_multiple_bond" title="Metal–ligand multiple bond">Metal–ligand multiple bond</a></li> <li><a href="/wiki/Charge-shift_bond" title="Charge-shift bond">Charge-shift</a></li> <li><a href="/wiki/Hapticity" title="Hapticity">Hapticity</a></li> <li><a href="/wiki/Conjugated_system" title="Conjugated system">Conjugation</a></li> <li><a class="mw-selflink selflink">Hyperconjugation</a></li> <li><a href="/wiki/Aromaticity" title="Aromaticity">Aromaticity</a> <ul><li><a href="/wiki/Homoaromaticity" title="Homoaromaticity">homo</a></li> <li><a href="/wiki/Bicycloaromaticity" title="Bicycloaromaticity">bicyclo</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Metallic_bonding" title="Metallic bonding">Metallic</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Metal_aromaticity" title="Metal aromaticity">Metal aromaticity</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Ionic_bonding" title="Ionic bonding">Ionic</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li class="mw-empty-elt"></li></ul> </div></td></tr></tbody></table><div></div></td><td class="noviewer navbox-image" rowspan="4" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"><a href="/wiki/File:Ligatio-covalens.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/21/Ligatio-covalens.svg/200px-Ligatio-covalens.svg.png" decoding="async" width="200" height="89" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/21/Ligatio-covalens.svg/300px-Ligatio-covalens.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/21/Ligatio-covalens.svg/400px-Ligatio-covalens.svg.png 2x" data-file-width="597" data-file-height="265" /></a></span><br /><span typeof="mw:File"><a href="/wiki/File:Chemfm_carbon_monoxide_3_1.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/77/Chemfm_carbon_monoxide_3_1.svg/200px-Chemfm_carbon_monoxide_3_1.svg.png" decoding="async" width="200" height="113" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/77/Chemfm_carbon_monoxide_3_1.svg/300px-Chemfm_carbon_monoxide_3_1.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/77/Chemfm_carbon_monoxide_3_1.svg/400px-Chemfm_carbon_monoxide_3_1.svg.png 2x" data-file-width="99" data-file-height="56" /></a></span><br /><span typeof="mw:File"><a href="/wiki/File:Pi-Bond.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Pi-Bond.svg/200px-Pi-Bond.svg.png" decoding="async" width="200" height="113" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Pi-Bond.svg/300px-Pi-Bond.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/70/Pi-Bond.svg/400px-Pi-Bond.svg.png 2x" data-file-width="1920" data-file-height="1080" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Intermolecular_force" title="Intermolecular force">Intermolecular</a><br />(weak)</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Van_der_Waals_force" title="Van der Waals force">Van der Waals<br />forces</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/London_dispersion_force" title="London dispersion force">London dispersion</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Hydrogen_bond" title="Hydrogen bond">Hydrogen</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Low-barrier_hydrogen_bond" title="Low-barrier hydrogen bond">Low-barrier</a></li> <li><a href="/wiki/Resonance-assisted_hydrogen_bond" class="mw-redirect" title="Resonance-assisted hydrogen bond">Resonance-assisted</a></li> <li><a href="/wiki/Symmetric_hydrogen_bond" title="Symmetric hydrogen bond">Symmetric</a></li> <li><a href="/wiki/Dihydrogen_bond" title="Dihydrogen bond">Dihydrogen bonds</a></li> <li><a href="/wiki/C%E2%80%93H%C2%B7%C2%B7%C2%B7O_interaction" title="C–H···O interaction">C–H···O interaction</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Non-covalent_interactions" class="mw-redirect" title="Non-covalent interactions">Noncovalent</a><br />other</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Mechanically_interlocked_molecular_architectures" title="Mechanically interlocked molecular architectures">Mechanical</a></li> <li><a href="/wiki/Halogen_bond" title="Halogen bond">Halogen</a></li> <li><a href="/wiki/Chalcogen_bond" title="Chalcogen bond">Chalcogen</a></li> <li><a href="/wiki/Metallophilic_interaction" title="Metallophilic interaction">Metallophilic</a> (<a href="/wiki/Aurophilicity" title="Aurophilicity">aurophilic</a>)</li> <li><a href="/wiki/Intercalation_(chemistry)" title="Intercalation (chemistry)">Intercalation</a></li> <li><a href="/wiki/Stacking_(chemistry)" title="Stacking (chemistry)">Stacking</a></li> <li><a href="/wiki/Cation%E2%80%93pi_interaction" class="mw-redirect" title="Cation–pi interaction">Cation–pi</a></li> <li><a href="/wiki/Cation%E2%80%93pi_interaction#Anion–π_interaction" class="mw-redirect" title="Cation–pi interaction">Anion–pi</a></li> <li><a href="/wiki/Salt_bridge_(protein_and_supramolecular)" title="Salt bridge (protein and supramolecular)">Salt bridge</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Bond_cleavage" title="Bond cleavage">Bond cleavage</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Heterolysis_(chemistry)" title="Heterolysis (chemistry)">Heterolysis</a></li> <li><a href="/wiki/Homolysis_(chemistry)" title="Homolysis (chemistry)">Homolysis</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Electron_counting" title="Electron counting">Electron counting</a> rules</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aromaticity" title="Aromaticity">Aromaticity</a> <ul><li><a href="/wiki/H%C3%BCckel%27s_rule" title="Hückel's rule">Hückel's rule</a></li> <li><a href="/wiki/Baird%27s_rule" title="Baird's rule">Baird's rule</a></li> <li><a href="/wiki/M%C3%B6bius_aromaticity" title="Möbius aromaticity">Möbius</a></li> <li><a href="/wiki/Spherical_aromaticity" title="Spherical aromaticity">spherical</a></li></ul></li> <li><a href="/wiki/Polyhedral_skeletal_electron_pair_theory" title="Polyhedral skeletal electron pair theory">Polyhedral skeletal electron pair theory</a></li> <li><a href="/wiki/Jemmis_mno_rules" title="Jemmis mno rules">Jemmis mno rules</a></li></ul> </div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Hyperconjugation&oldid=1221687648">https://en.wikipedia.org/w/index.php?title=Hyperconjugation&oldid=1221687648</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Category</a>: <ul><li><a href="/wiki/Category:Physical_organic_chemistry" title="Category:Physical organic chemistry">Physical organic chemistry</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_is_different_from_Wikidata" title="Category:Short description is different from Wikidata">Short description is different from Wikidata</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 1 May 2024, at 12:04<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. By using this site, you agree to the <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Terms_of_Use" class="extiw" title="foundation:Special:MyLanguage/Policy:Terms of Use">Terms of Use</a> and <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy" class="extiw" title="foundation:Special:MyLanguage/Policy:Privacy policy">Privacy Policy</a>. Wikipedia® is a registered trademark of the <a rel="nofollow" class="external text" href="https://wikimediafoundation.org/">Wikimedia Foundation, Inc.</a>, a non-profit organization.</li> </ul> <ul id="footer-places"> <li id="footer-places-privacy"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/wiki/Wikipedia:About">About Wikipedia</a></li> <li id="footer-places-disclaimers"><a href="/wiki/Wikipedia:General_disclaimer">Disclaimers</a></li> <li id="footer-places-contact"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact Wikipedia</a></li> <li id="footer-places-wm-codeofconduct"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Universal_Code_of_Conduct">Code of Conduct</a></li> <li id="footer-places-developers"><a href="https://developer.wikimedia.org">Developers</a></li> <li id="footer-places-statslink"><a href="https://stats.wikimedia.org/#/en.wikipedia.org">Statistics</a></li> <li id="footer-places-cookiestatement"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Cookie_statement">Cookie statement</a></li> <li id="footer-places-mobileview"><a href="//en.m.wikipedia.org/w/index.php?title=Hyperconjugation&mobileaction=toggle_view_mobile" class="noprint stopMobileRedirectToggle">Mobile view</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"><a href="https://wikimediafoundation.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/static/images/footer/wikimedia-button.svg" width="84" height="29" alt="Wikimedia Foundation" loading="lazy"></a></li> <li id="footer-poweredbyico"><a href="https://www.mediawiki.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><img src="/w/resources/assets/poweredby_mediawiki.svg" alt="Powered by MediaWiki" width="88" height="31" loading="lazy"></a></li> </ul> </footer> </div> </div> </div> <div class="vector-settings" id="p-dock-bottom"> <ul></ul> </div><script>(RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgHostname":"mw-web.codfw.main-f69cdc8f6-7dxkw","wgBackendResponseTime":142,"wgPageParseReport":{"limitreport":{"cputime":"0.393","walltime":"0.520","ppvisitednodes":{"value":1617,"limit":1000000},"postexpandincludesize":{"value":53763,"limit":2097152},"templateargumentsize":{"value":711,"limit":2097152},"expansiondepth":{"value":16,"limit":100},"expensivefunctioncount":{"value":1,"limit":500},"unstrip-depth":{"value":1,"limit":20},"unstrip-size":{"value":75460,"limit":5000000},"entityaccesscount":{"value":0,"limit":400},"timingprofile":["100.00% 411.368 1 -total"," 51.82% 213.154 1 Template:Reflist"," 27.67% 113.822 14 Template:Cite_journal"," 26.95% 110.843 3 Template:Navbox"," 26.77% 110.119 1 Template:Chemical_bonds"," 17.93% 73.765 1 Template:Short_description"," 12.50% 51.419 1 Template:GoldBookRef"," 11.16% 45.899 2 Template:Doi"," 10.84% 44.586 2 Template:Pagetype"," 10.22% 42.054 3 Template:Catalog_lookup_link"]},"scribunto":{"limitreport-timeusage":{"value":"0.227","limit":"10.000"},"limitreport-memusage":{"value":5664453,"limit":52428800}},"cachereport":{"origin":"mw-web.codfw.main-f69cdc8f6-xvj4r","timestamp":"20241122141517","ttl":2592000,"transientcontent":false}}});});</script> <script type="application/ld+json">{"@context":"https:\/\/schema.org","@type":"Article","name":"Hyperconjugation","url":"https:\/\/en.wikipedia.org\/wiki\/Hyperconjugation","sameAs":"http:\/\/www.wikidata.org\/entity\/Q899217","mainEntity":"http:\/\/www.wikidata.org\/entity\/Q899217","author":{"@type":"Organization","name":"Contributors to Wikimedia projects"},"publisher":{"@type":"Organization","name":"Wikimedia Foundation, Inc.","logo":{"@type":"ImageObject","url":"https:\/\/www.wikimedia.org\/static\/images\/wmf-hor-googpub.png"}},"datePublished":"2005-09-22T06:16:41Z","dateModified":"2024-05-01T12:04:32Z","image":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/1\/11\/Alkene-hyperconjugation2.png","headline":"interaction of the electrons in a sigma bond with an adjacent empty (or partially filled) non-bonding p-orbital, antibonding \u03c3 or \u03c0 orbital, or filled \u03c0 orbital, to give an extended molecular orbital that increases the stability of the system"}</script> </body> </html>