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<ul id="toc-Structural_isomers-sublist" class="vector-toc-list"> <li id="toc-Example:_C3H8O" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Example:_C3H8O"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>Example: <span>C<span><span><sup></sup><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">3</sub></span></span>H<span><span><sup></sup><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">8</sub></span></span>O</span></span> </div> </a> <ul id="toc-Example:_C3H8O-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Example:_C3H4" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Example:_C3H4"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.2</span> <span>Example: <span>C<span><span><sup></sup><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">3</sub></span></span>H<span><span><sup></sup><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">4</sub></span></span></span></span> </div> </a> <ul id="toc-Example:_C3H4-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Tautomers" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Tautomers"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.3</span> <span>Tautomers</span> </div> </a> <ul id="toc-Tautomers-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Stereoisomers" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Stereoisomers"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Stereoisomers</span> </div> </a> <button aria-controls="toc-Stereoisomers-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 Stereoisomers subsection</span> </button> <ul id="toc-Stereoisomers-sublist" class="vector-toc-list"> <li id="toc-Enantiomers" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Enantiomers"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.1</span> <span>Enantiomers</span> </div> </a> <ul id="toc-Enantiomers-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Diastereomers" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Diastereomers"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2</span> <span>Diastereomers</span> </div> </a> <ul id="toc-Diastereomers-sublist" class="vector-toc-list"> <li id="toc-Cis-trans_isomerism" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Cis-trans_isomerism"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.2.1</span> <span>Cis-trans isomerism</span> </div> </a> <ul id="toc-Cis-trans_isomerism-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> </ul> </li> <li id="toc-Isotopes_and_spin" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Isotopes_and_spin"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Isotopes and spin</span> </div> </a> <button aria-controls="toc-Isotopes_and_spin-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 Isotopes and spin subsection</span> </button> <ul id="toc-Isotopes_and_spin-sublist" class="vector-toc-list"> <li id="toc-Isotopomers" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Isotopomers"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Isotopomers</span> </div> </a> <ul id="toc-Isotopomers-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Spin_isomers" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Spin_isomers"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Spin isomers</span> </div> </a> <ul id="toc-Spin_isomers-sublist" class="vector-toc-list"> </ul> </li> </ul> </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">4</span> <span>Applications</span> </div> </a> <ul id="toc-Applications-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-History" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#History"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>History</span> </div> </a> <ul id="toc-History-sublist" class="vector-toc-list"> </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">6</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">7</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">8</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" title="Table of Contents" > <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">Isomer</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 52 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-52" 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">52 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Isomeer" title="Isomeer – Afrikaans" lang="af" hreflang="af" data-title="Isomeer" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%AA%D8%B5%D8%A7%D9%88%D8%BA" title="تصاوغ – Arabic" lang="ar" hreflang="ar" data-title="تصاوغ" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%B8%E0%A6%AE%E0%A6%BE%E0%A6%A3%E0%A7%81" title="সমাণু – Bangla" lang="bn" hreflang="bn" data-title="সমাণু" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Izomeri" title="Izomeri – Bosnian" lang="bs" hreflang="bs" data-title="Izomeri" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Is%C3%B2mer" title="Isòmer – Catalan" lang="ca" hreflang="ca" data-title="Isòmer" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cy mw-list-item"><a href="https://cy.wikipedia.org/wiki/Isomer" title="Isomer – Welsh" lang="cy" hreflang="cy" data-title="Isomer" data-language-autonym="Cymraeg" data-language-local-name="Welsh" class="interlanguage-link-target"><span>Cymraeg</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Isomer" title="Isomer – Danish" lang="da" hreflang="da" data-title="Isomer" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de badge-Q70894304 mw-list-item" title=""><a href="https://de.wikipedia.org/wiki/Isomer" title="Isomer – German" lang="de" hreflang="de" data-title="Isomer" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Isomeerid" title="Isomeerid – Estonian" lang="et" hreflang="et" data-title="Isomeerid" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Isomer%C3%ADa" title="Isomería – Spanish" lang="es" hreflang="es" data-title="Isomería" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Izomero" title="Izomero – Esperanto" lang="eo" hreflang="eo" data-title="Izomero" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Isomero" title="Isomero – Basque" lang="eu" hreflang="eu" data-title="Isomero" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%87%D9%85%D9%BE%D8%A7%D8%B1" title="همپار – Persian" lang="fa" hreflang="fa" data-title="همپار" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr badge-Q70893996 mw-list-item" title=""><a href="https://fr.wikipedia.org/wiki/Isom%C3%A8re" title="Isomère – French" lang="fr" hreflang="fr" data-title="Isomère" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Isim%C3%A9ir" title="Isiméir – Irish" lang="ga" hreflang="ga" data-title="Isiméir" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-gu mw-list-item"><a href="https://gu.wikipedia.org/wiki/%E0%AA%B8%E0%AA%AE%E0%AA%98%E0%AA%9F%E0%AA%95%E0%AA%A4%E0%AA%BE" title="સમઘટકતા – Gujarati" lang="gu" hreflang="gu" data-title="સમઘટકતા" data-language-autonym="ગુજરાતી" data-language-local-name="Gujarati" class="interlanguage-link-target"><span>ગુજરાતી</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EC%9D%B4%EC%84%B1%EC%A7%88%EC%B2%B4" title="이성질체 – Korean" lang="ko" hreflang="ko" data-title="이성질체" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%B8%E0%A4%AE%E0%A4%BE%E0%A4%B5%E0%A4%AF%E0%A4%B5%E0%A5%80" title="समावयवी – Hindi" lang="hi" hreflang="hi" data-title="समावयवी" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Izomer" title="Izomer – Croatian" lang="hr" hreflang="hr" data-title="Izomer" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Isomer" title="Isomer – Indonesian" lang="id" hreflang="id" data-title="Isomer" 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-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%90%D7%99%D7%96%D7%95%D7%9E%D7%A8" title="איזומר – Hebrew" lang="he" hreflang="he" data-title="איזומר" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-kn mw-list-item"><a href="https://kn.wikipedia.org/wiki/%E0%B2%90%E0%B2%B8%E0%B3%8B%E0%B2%AE%E0%B2%B0%E0%B3%8D" title="ಐಸೋಮರ್ – Kannada" lang="kn" hreflang="kn" data-title="ಐಸೋಮರ್" data-language-autonym="ಕನ್ನಡ" data-language-local-name="Kannada" class="interlanguage-link-target"><span>ಕನ್ನಡ</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%98%E1%83%96%E1%83%9D%E1%83%9B%E1%83%94%E1%83%A0%E1%83%98%E1%83%90" title="იზომერია – Georgian" lang="ka" hreflang="ka" data-title="იზომერია" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%98%D0%B7%D0%BE%D0%BC%D0%B5%D1%80%D0%B0%D0%BB%D0%B0%D1%80" title="Изомералар – Kazakh" lang="kk" hreflang="kk" data-title="Изомералар" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-ht mw-list-item"><a href="https://ht.wikipedia.org/wiki/Izom%C3%A8" title="Izomè – Haitian Creole" lang="ht" hreflang="ht" data-title="Izomè" data-language-autonym="Kreyòl ayisyen" data-language-local-name="Haitian Creole" class="interlanguage-link-target"><span>Kreyòl ayisyen</span></a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%98%D0%B7%D0%BE%D0%BC%D0%B5%D1%80%D0%BB%D0%B5%D1%80" title="Изомерлер – Kyrgyz" lang="ky" hreflang="ky" data-title="Изомерлер" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%90%E0%B4%B8%E0%B5%8B%E0%B4%AE%E0%B5%86%E0%B5%BC" title="ഐസോമെർ – Malayalam" lang="ml" hreflang="ml" data-title="ഐസോമെർ" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Isomer" title="Isomer – Malay" lang="ms" hreflang="ms" data-title="Isomer" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Isomeer" title="Isomeer – Dutch" lang="nl" hreflang="nl" data-title="Isomeer" 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/%E7%95%B0%E6%80%A7%E4%BD%93" title="異性体 – Japanese" lang="ja" hreflang="ja" data-title="異性体" 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-frr badge-Q70894304 mw-list-item" title=""><a href="https://frr.wikipedia.org/wiki/Isomeeren" title="Isomeeren – Northern Frisian" lang="frr" hreflang="frr" data-title="Isomeeren" data-language-autonym="Nordfriisk" data-language-local-name="Northern Frisian" class="interlanguage-link-target"><span>Nordfriisk</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Isomer_(isotop)" title="Isomer (isotop) – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Isomer (isotop)" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-om mw-list-item"><a href="https://om.wikipedia.org/wiki/Ayisoomeriizimii" title="Ayisoomeriizimii – Oromo" lang="om" hreflang="om" data-title="Ayisoomeriizimii" data-language-autonym="Oromoo" data-language-local-name="Oromo" class="interlanguage-link-target"><span>Oromoo</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Izomery" title="Izomery – Polish" lang="pl" hreflang="pl" data-title="Izomery" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-ru badge-Q70894304 mw-list-item" title=""><a href="https://ru.wikipedia.org/wiki/%D0%98%D0%B7%D0%BE%D0%BC%D0%B5%D1%80" title="Изомер – Russian" lang="ru" hreflang="ru" data-title="Изомер" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sq mw-list-item"><a href="https://sq.wikipedia.org/wiki/Izomeri" title="Izomeri – Albanian" lang="sq" hreflang="sq" data-title="Izomeri" data-language-autonym="Shqip" data-language-local-name="Albanian" class="interlanguage-link-target"><span>Shqip</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Isomer" title="Isomer – Simple English" lang="en-simple" hreflang="en-simple" data-title="Isomer" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Izomer" title="Izomer – Slovenian" lang="sl" hreflang="sl" data-title="Izomer" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-ckb mw-list-item"><a href="https://ckb.wikipedia.org/wiki/%D8%A6%D8%A7%DB%8C%D8%B2%DB%86%D9%85%DB%95%D8%B1" title="ئایزۆمەر – Central Kurdish" lang="ckb" hreflang="ckb" data-title="ئایزۆمەر" data-language-autonym="کوردی" data-language-local-name="Central Kurdish" class="interlanguage-link-target"><span>کوردی</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%98%D0%B7%D0%BE%D0%BC%D0%B5%D1%80_(%D1%85%D0%B5%D0%BC%D0%B8%D1%98%D1%81%D0%BA%D0%B8)" title="Изомер (хемијски) – Serbian" lang="sr" hreflang="sr" data-title="Изомер (хемијски)" 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/Izomeri" title="Izomeri – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Izomeri" 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-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%9A%E0%AE%AE%E0%AE%AA%E0%AE%95%E0%AF%81%E0%AE%A4%E0%AE%BF%E0%AE%AF%E0%AE%AE%E0%AF%8D" title="சமபகுதியம் – Tamil" lang="ta" hreflang="ta" data-title="சமபகுதியம்" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-tt mw-list-item"><a href="https://tt.wikipedia.org/wiki/%C4%B0zomerlar" title="İzomerlar – Tatar" lang="tt" hreflang="tt" data-title="İzomerlar" data-language-autonym="Татарча / tatarça" data-language-local-name="Tatar" class="interlanguage-link-target"><span>Татарча / tatarça</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B9%84%E0%B8%AD%E0%B9%82%E0%B8%8B%E0%B9%80%E0%B8%A1%E0%B8%AD%E0%B8%A3%E0%B9%8C" title="ไอโซเมอร์ – Thai" lang="th" hreflang="th" data-title="ไอโซเมอร์" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/%C4%B0zomer" title="İzomer – Turkish" lang="tr" hreflang="tr" data-title="İzomer" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk badge-Q70893996 mw-list-item" title=""><a href="https://uk.wikipedia.org/wiki/%D0%86%D0%B7%D0%BE%D0%BC%D0%B5%D1%80%D0%B8" title="Ізомери – Ukrainian" lang="uk" hreflang="uk" data-title="Ізомери" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-ur mw-list-item"><a href="https://ur.wikipedia.org/wiki/%DB%81%D9%85_%D8%AC%D8%B2%D8%A1" title="ہم جزء – Urdu" lang="ur" hreflang="ur" data-title="ہم جزء" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/%C4%90%E1%BB%93ng_ph%C3%A2n" title="Đồng phân – Vietnamese" lang="vi" hreflang="vi" data-title="Đồng phân" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link 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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">Chemical compounds with the same molecular formula but different atomic arrangements</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">This article is about the chemical concept. For "isomerism" of atomic nuclei, see <a href="/wiki/Nuclear_isomer" title="Nuclear isomer">nuclear isomer</a>. For part of the body of the proarticulates, see <a href="/wiki/Isomer_(Proarticulata)" title="Isomer (Proarticulata)">isomer (Proarticulata)</a>.</div> <p class="mw-empty-elt"> </p><p>In <a href="/wiki/Chemistry" title="Chemistry">chemistry</a>, <b>isomers</b> are <a href="/wiki/Molecule" title="Molecule">molecules</a> or <a href="/wiki/Polyatomic_ion" title="Polyatomic ion">polyatomic ions</a> with identical <a href="/wiki/Molecular_formula" class="mw-redirect" title="Molecular formula">molecular formula</a> – that is, the same number of <a href="/wiki/Atom" title="Atom">atoms</a> of each <a href="/wiki/Element_(chemistry)" class="mw-redirect" title="Element (chemistry)">element</a> – but distinct arrangements of atoms in space.<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> <i>Isomerism</i> refers to the existence or possibility of isomers. </p><p>Isomers do not necessarily share similar <a href="/wiki/Chemical_property" title="Chemical property">chemical</a> or <a href="/wiki/Physical_property" title="Physical property">physical properties</a>. Two main forms of isomerism are <a href="/wiki/Structural_isomerism" class="mw-redirect" title="Structural isomerism">structural</a> (or constitutional) isomerism, in which <i><a href="/wiki/Chemical_bond" title="Chemical bond">bonds</a></i> between the atoms differ; and <a href="/wiki/Stereoisomerism" title="Stereoisomerism">stereoisomerism</a> (or spatial isomerism), in which the bonds are the same but the <i>relative positions</i> of the atoms differ. </p><p>Isomeric relationships form a <a href="/wiki/Hierarchy" title="Hierarchy">hierarchy</a>. Two chemicals might be the same constitutional isomer, but upon deeper analysis be stereoisomers of each other. Two molecules that are the same stereoisomer as each other might be in different conformational forms or be different <a href="/wiki/Isotopologue" title="Isotopologue">isotopologues</a>. The depth of analysis depends on the field of study or the chemical and physical properties of interest. </p><p>The English word "isomer" (<span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="/ˈ/: primary stress follows">ˈ</span><span title="/aɪ/: 'i' in 'tide'">aɪ</span><span title="'s' in 'sigh'">s</span><span title="/əm/: 'm' in 'rhythm'">əm</span><span title="/ər/: 'er' in 'letter'">ər</span></span>/</a></span></span>) is a <a href="/wiki/Back-formation" title="Back-formation">back-formation</a> from "isomeric",<sup id="cite_ref-MW.isomer_2-0" class="reference"><a href="#cite_note-MW.isomer-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> which was borrowed through <a href="/wiki/German_language" title="German language">German</a> <i>isomerisch</i><sup id="cite_ref-MW.isomeric_3-0" class="reference"><a href="#cite_note-MW.isomeric-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> from <a href="/wiki/Swedish_language" title="Swedish language">Swedish</a> <span title="Swedish-language text"><i lang="sv">isomerisk</i></span>; which in turn was coined from <a href="/wiki/Greek_language" title="Greek language">Greek</a> ἰσόμερoς <span title="Ancient Greek (to 1453)-language romanization"><i lang="grc-Latn">isómeros</i></span>, with roots <span title="Ancient Greek (to 1453)-language romanization"><i lang="grc-Latn">isos</i></span> = "equal", <span title="Ancient Greek (to 1453)-language romanization"><i lang="grc-Latn">méros</i></span> = "part".<sup id="cite_ref-berz1830_4-0" class="reference"><a href="#cite_note-berz1830-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size mw-halign-center" typeof="mw:File/Thumb"><a href="/wiki/File:IsomerOverview.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4b/IsomerOverview.svg/250px-IsomerOverview.svg.png" decoding="async" width="220" height="110" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4b/IsomerOverview.svg/330px-IsomerOverview.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4b/IsomerOverview.svg/440px-IsomerOverview.svg.png 2x" data-file-width="283" data-file-height="141" /></a><figcaption>Two broad types of isomers</figcaption></figure> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Structural_isomers">Structural isomers</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=1" title="Edit section: Structural isomers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Structural_isomer" title="Structural isomer">Structural isomer</a></div> <p><b>Structural isomers</b> have the same number of atoms of each element (hence the same <a href="/wiki/Molecular_formula" class="mw-redirect" title="Molecular formula">molecular formula</a>), but the atoms are connected in distinct ways.<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> </p> <div class="mw-heading mw-heading3"><h3 id="Example:_C3H8O">Example: <span class="chemf nowrap">C<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">3</sub></span></span>H<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">8</sub></span></span>O</span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=2" title="Edit section: Example: C3H8O"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>For example, there are three distinct compounds with the molecular formula <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {C3H8O}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>8</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>O</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {C3H8O}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8c41f8d557f0a16aa1dd809d618dbbe7cf1729c1" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:7.338ex; height:2.843ex;" alt="{\displaystyle {\ce {C3H8O}}}" /></span>: </p> <figure class="mw-halign-center skin-invert-image" typeof="mw:File"><a href="/wiki/File:Structural_isomers.svg" class="mw-file-description" title="Structural isomers of C 3H 8O: I 1-propanol, II 2-propanol, III ethyl-methyl-ether."><img alt="Structural isomers of C 3H 8O: I 1-propanol, II 2-propanol, III ethyl-methyl-ether." src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Structural_isomers.svg/500px-Structural_isomers.svg.png" decoding="async" width="500" height="158" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Structural_isomers.svg/960px-Structural_isomers.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Structural_isomers.svg/1000px-Structural_isomers.svg.png 2x" data-file-width="1360" data-file-height="430" /></a><figcaption>Structural isomers of <span class="chemf nowrap">C<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">3</sub></span></span>H<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">8</sub></span></span>O</span>: <b>I</b> 1-propanol, <b>II</b> 2-propanol, <b>III</b> ethyl-methyl-ether.</figcaption></figure> <p>The first two isomers shown of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {C3H8O}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>8</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>O</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {C3H8O}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8c41f8d557f0a16aa1dd809d618dbbe7cf1729c1" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:7.338ex; height:2.843ex;" alt="{\displaystyle {\ce {C3H8O}}}" /></span> are <a href="/wiki/Propanol" title="Propanol">propanols</a>, that is, <a href="/wiki/Alcohol_(chemistry)" title="Alcohol (chemistry)">alcohols</a> derived from <a href="/wiki/Propane" title="Propane">propane</a>. Both have a chain of three carbon atoms connected by single bonds, with the remaining carbon <a href="/wiki/Valence_(chemistry)" title="Valence (chemistry)">valences</a> being filled by seven <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a> atoms and by a <a href="/wiki/Hydroxyl" class="mw-redirect" title="Hydroxyl">hydroxyl</a> group <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {-OH}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>OH</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {-OH}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a5328d8e0b5cd0c3639195893ea742237999a572" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:5.359ex; height:2.343ex;" alt="{\displaystyle {\ce {-OH}}}" /></span> comprising the <a href="/wiki/Oxygen" title="Oxygen">oxygen</a> atom bound to a hydrogen atom. These two isomers differ on which carbon the hydroxyl is bound to: either to an extremity of the carbon chain <a href="/wiki/Propan-1-ol" class="mw-redirect" title="Propan-1-ol">propan-1-ol</a> (1-propanol, <i>n</i>-propyl alcohol, <i>n</i>-propanol; <b>I</b>) or to the middle carbon <a href="/wiki/Propan-2-ol" class="mw-redirect" title="Propan-2-ol">propan-2-ol</a> (2-propanol, isopropyl alcohol, isopropanol; <b>II</b>). These can be described by the <a href="/wiki/Structural_formula#Condensed_formula" title="Structural formula">condensed structural formulas</a> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {H3C-CH2-CH2OH}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>OH</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {H3C-CH2-CH2OH}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6d4c1afb5919de9c5e518068570204cfefae7675" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:20.594ex; height:2.843ex;" alt="{\displaystyle {\ce {H3C-CH2-CH2OH}}}" /></span> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {H3C-CH(OH)-CH3}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">(</mo> <mtext>OH</mtext> <mo stretchy="false">)</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {H3C-CH(OH)-CH3}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e6d4babdd48d017f53a22e9db02c770baedd7f1d" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:21.349ex; height:3.009ex;" alt="{\displaystyle {\ce {H3C-CH(OH)-CH3}}}" /></span>. </p><p>The third isomer of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {C3H8O}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>8</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>O</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {C3H8O}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8c41f8d557f0a16aa1dd809d618dbbe7cf1729c1" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:7.338ex; height:2.843ex;" alt="{\displaystyle {\ce {C3H8O}}}" /></span> is the <a href="/wiki/Ether" title="Ether">ether</a> <a href="/wiki/Methoxyethane" title="Methoxyethane">methoxyethane</a> (ethyl-methyl-ether; <b>III</b>). Unlike the other two, it has the oxygen atom connected to two carbons, and all eight hydrogens bonded directly to carbons. It can be described by the condensed formula <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {H3C-CH2-O-CH3}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>O</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {H3C-CH2-O-CH3}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e22802c7812dc66a3f2429a9c666294d15ad9a41" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:20.659ex; height:2.843ex;" alt="{\displaystyle {\ce {H3C-CH2-O-CH3}}}" /></span>. </p><p>The alcohol "3-propanol" is not another isomer, since the difference between it and 1-propanol is not real; it is only the result of an arbitrary choice in the direction of numbering the carbons along the chain. For the same reason, "ethoxymethane" is the same molecule as methoxyethane, not another isomer. </p><p>1-Propanol and 2-propanol are examples of <a href="/wiki/Structural_isomer#Position_isomerism_(regioisomerism)" title="Structural isomer">positional isomers</a>, which differ by the position at which certain features, such as <a href="/wiki/Double_bond" title="Double bond">double bonds</a> or <a href="/wiki/Functional_group" title="Functional group">functional groups</a>, occur on a "parent" molecule (propane, in that case). </p> <div class="mw-heading mw-heading3"><h3 id="Example:_C3H4">Example: <span class="chemf nowrap">C<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">3</sub></span></span>H<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">4</sub></span></span></span></h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=3" title="Edit section: Example: C3H4"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>There are also three structural isomers of the <a href="/wiki/Hydrocarbon" title="Hydrocarbon">hydrocarbon</a> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {C3H4}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {C3H4}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e88ccb88e7aad14abce97dc1efee289f5d17c7fc" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:5.53ex; height:2.843ex;" alt="{\displaystyle {\ce {C3H4}}}" /></span>: </p> <table style="margin-left:auto; margin-right:auto; border:none;" class="skin-invert-image"> <tbody><tr> <td style="padding: 0px 20px 0px;"><span typeof="mw:File"><a href="/wiki/File:Propadiene_structure.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Propadiene_structure.svg/250px-Propadiene_structure.svg.png" decoding="async" width="150" height="93" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Propadiene_structure.svg/300px-Propadiene_structure.svg.png 2x" data-file-width="290" data-file-height="180" /></a></span> </td> <td style="padding: 0px 20px 0px;"><span typeof="mw:File"><a href="/wiki/File:Propyne-2D-flat.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Propyne-2D-flat.png/150px-Propyne-2D-flat.png" decoding="async" width="150" height="90" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Propyne-2D-flat.png/225px-Propyne-2D-flat.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Propyne-2D-flat.png/300px-Propyne-2D-flat.png 2x" data-file-width="1100" data-file-height="663" /></a></span> </td> <td style="padding: 0px 20px 0px;"><span typeof="mw:File"><a href="/wiki/File:Cyclopropene.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/64/Cyclopropene.png/100px-Cyclopropene.png" decoding="async" width="100" height="62" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/64/Cyclopropene.png/150px-Cyclopropene.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/64/Cyclopropene.png/200px-Cyclopropene.png 2x" data-file-width="1398" data-file-height="864" /></a></span> </td></tr> <tr> <td style="text-align:center;padding-left=20px;"><b>I</b> Propadiene </td> <td style="text-align:center;padding-left=20px;"><b>II</b> Propyne </td> <td style="text-align:center;padding-left=20px;"><b>III</b> Cyclopropene </td></tr> </tbody></table> <p>In two of the isomers, the three carbon atoms are connected in an open chain, but in one of them (<a href="/wiki/Propadiene" title="Propadiene">propadiene</a> or allene; <b>I</b>) the carbons are connected by two <a href="/wiki/Double_bond" title="Double bond">double bonds</a>, while in the other (<a href="/wiki/Propyne" title="Propyne">propyne</a> or methylacetylene; <b>II</b>) they are connected by a single bond and a <a href="/wiki/Triple_bond" title="Triple bond">triple bond</a>. In the third isomer (<a href="/wiki/Cyclopropene" title="Cyclopropene">cyclopropene</a>; <b>III</b>) the three carbons are connected into a ring by two single bonds and a double bond. In all three, the remaining valences of the carbon atoms are satisfied by the four hydrogens. </p><p>Again, note that there is only one structural isomer with a triple bond, because the other possible placement of that bond is just drawing the three carbons in a different order. For the same reason, there is only one cyclopropene, not three. </p> <div class="mw-heading mw-heading3"><h3 id="Tautomers">Tautomers</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=4" title="Edit section: Tautomers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Tautomer" title="Tautomer">Tautomers</a> are structural isomers which readily interconvert, so that two or more species co-exist in equilibrium such as </p><p><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {H-X-Y=Z <=> X=Y-Z-H}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>X</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>Y</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>=</mo> </mrow> <mtext>Z</mtext> <mrow class="MJX-TeXAtom-REL"> <mover> <mrow class="MJX-TeXAtom-OP MJX-fixedlimits"> <mrow class="MJX-TeXAtom-ORD"> <mpadded height="0" depth="0"> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">↽</mo> </mrow> <mspace width="negativethinmathspace"></mspace> <mspace width="negativethinmathspace"></mspace> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> </mpadded> </mrow> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mspace width="negativethinmathspace"></mspace> <mspace width="negativethinmathspace"></mspace> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">⇀</mo> </mrow> </mrow> </mstyle> </mrow> </mover> </mrow> <mtext>X</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>=</mo> </mrow> <mtext>Y</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>Z</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>H</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {H-X-Y=Z <=> X=Y-Z-H}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f84bf46bee770ff40f7e46fe32c448c792b30ad1" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:28.796ex; height:2.843ex;" alt="{\displaystyle {\ce {H-X-Y=Z <=> X=Y-Z-H}}}" /></span>.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>Important examples are <a href="/wiki/Keto-enol_tautomerism" class="mw-redirect" title="Keto-enol tautomerism">keto-enol tautomerism</a> and the equilibrium between neutral and <a href="/wiki/Zwitterionic" class="mw-redirect" title="Zwitterionic">zwitterionic</a> forms of an <a href="/wiki/Amino_acid" title="Amino acid">amino acid</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Stereoisomers">Stereoisomers</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=5" title="Edit section: Stereoisomers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-center" typeof="mw:File/Thumb"><a href="/wiki/File:Stereoisomer_are_of_two_types,_enantiomers_vs_diastereomers.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e2/Stereoisomer_are_of_two_types%2C_enantiomers_vs_diastereomers.svg/200px-Stereoisomer_are_of_two_types%2C_enantiomers_vs_diastereomers.svg.png" decoding="async" width="200" height="79" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e2/Stereoisomer_are_of_two_types%2C_enantiomers_vs_diastereomers.svg/300px-Stereoisomer_are_of_two_types%2C_enantiomers_vs_diastereomers.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e2/Stereoisomer_are_of_two_types%2C_enantiomers_vs_diastereomers.svg/400px-Stereoisomer_are_of_two_types%2C_enantiomers_vs_diastereomers.svg.png 2x" data-file-width="283" data-file-height="112" /></a><figcaption>Two kinds of stereoisomers</figcaption></figure> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Stereoisomerism" title="Stereoisomerism">Stereoisomerism</a></div> <p>Stereoisomers have the same atoms or isotopes connected by bonds of the same type, but differ in the relative positions of those atoms in space. Two broad types of stereoisomers exist, enantiomers and diastereomers. Enantiomers have identical physical properties but diastereomers do not.<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> <div class="mw-heading mw-heading3"><h3 id="Enantiomers">Enantiomers</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=6" title="Edit section: Enantiomers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Two compounds are said to be <a href="/wiki/Enantiomer" title="Enantiomer">enantiomers</a> if their molecules are mirror images of each other and cannot be made to coincide only by rotations or translations – like a left hand and a right hand. The two shapes are said to be <a href="/wiki/Chirality" title="Chirality">chiral</a>. </p><p>A classic example is <a href="/wiki/Bromochlorofluoromethane" title="Bromochlorofluoromethane">bromochlorofluoromethane</a> (<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {CHFClBr}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>CHFClBr</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {CHFClBr}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/836fe1a0a1bf88f5b2fcb2374e190ffeb6055ff5" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:9.821ex; height:2.176ex;" alt="{\displaystyle {\ce {CHFClBr}}}" /></span>). The two enantiomers can be distinguished, for example, by whether the path <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {F->Cl->Br}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>F</mtext> <mo stretchy="false">⟶</mo> <mtext>Cl</mtext> <mo stretchy="false">⟶</mo> <mtext>Br</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {F->Cl->Br}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0aa83ad6ddea2ec268330f7a7af229bb109f9d39" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:16.592ex; height:2.176ex;" alt="{\displaystyle {\ce {F->Cl->Br}}}" /></span> turns clockwise or counterclockwise as seen from the hydrogen atom. In order to change one conformation to the other, at some point those four atoms would have to lie on the same plane – which would require severely straining or breaking their bonds to the carbon atom. The corresponding energy barrier between the two conformations is so high that there is practically no conversion between them at room temperature, and they can be regarded as different configurations. </p><p>The compound <a href="/wiki/Chlorofluoromethane" title="Chlorofluoromethane">chlorofluoromethane</a> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {CH2ClF}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>ClF</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {CH2ClF}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c2ca770cb7e661151541f802b072d03d313d86fe" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:8.318ex; height:2.843ex;" alt="{\displaystyle {\ce {CH2ClF}}}" /></span>, in contrast, is not chiral; the mirror image of its molecule is also obtained by a half-turn about a suitable axis. </p><p>Another example of a chiral compound is <a href="/wiki/Pentadiene" title="Pentadiene">2,3-pentadiene</a> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {H3C-CH=C=CH-CH3}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>=</mo> </mrow> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>=</mo> </mrow> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {H3C-CH=C=CH-CH3}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0b64d5144149f29e3b17437b9bc92d844ad2729e" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:24.704ex; height:2.843ex;" alt="{\displaystyle {\ce {H3C-CH=C=CH-CH3}}}" /></span>, a hydrocarbon that contains two overlapping double bonds. The double bonds are such that the three middle carbons are in a straight line, while the first three and last three lie on perpendicular planes. The molecule and its mirror image are not superimposable, even though the molecule has an axis of symmetry. The two enantiomers can be distinguished, for example, by the <a href="/wiki/Right-hand_rule" title="Right-hand rule">right-hand rule</a>. This type of isomerism is called <a href="/w/index.php?title=Axial_isomer&action=edit&redlink=1" class="new" title="Axial isomer (page does not exist)">axial isomerism</a>. </p><p>Enantiomers behave identically in chemical reactions, except when reacting with chiral compounds or in the presence of chiral <a href="/wiki/Catalysts" class="mw-redirect" title="Catalysts">catalysts</a>, such as most <a href="/wiki/Enzyme" title="Enzyme">enzymes</a>. For this latter reason, the two enantiomers of most chiral compounds usually have markedly different effects and roles in living organisms. In <a href="/wiki/Biochemistry" title="Biochemistry">biochemistry</a> and <a href="/wiki/Food_science" title="Food science">food science</a>, the two enantiomers of a chiral molecule – such as <a href="/wiki/Glucose" title="Glucose">glucose</a> – are usually identified and treated as very different substances. </p><p>Each enantiomer of a chiral compound typically rotates the plane of <a href="/wiki/Polarized_light" class="mw-redirect" title="Polarized light">polarized light</a> that passes through it. The rotation has the same magnitude but opposite senses for the two isomers, and can be a useful way of distinguishing and measuring their concentration in a solution. For this reason, enantiomers were formerly called "optical isomers".<sup id="cite_ref-FOOTNOTEPetrucciHarwoodHerring2002996–997_8-0" class="reference"><a href="#cite_note-FOOTNOTEPetrucciHarwoodHerring2002996–997-8"><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> However, this term is ambiguous and is discouraged by the <a href="/wiki/IUPAC" class="mw-redirect" title="IUPAC">IUPAC</a>.<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><sup id="cite_ref-Eliel2_11-0" class="reference"><a href="#cite_note-Eliel2-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p><p>Some enantiomer pairs (such as those of <a href="/wiki/Trans-Cyclooctene" title="Trans-Cyclooctene"><i>trans</i>-cyclooctene</a>) can be interconverted by internal motions that change bond lengths and angles only slightly. Other pairs (such as CHFClBr) cannot be interconverted without breaking bonds, and therefore are different configurations. </p> <div class="mw-heading mw-heading3"><h3 id="Diastereomers">Diastereomers</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=7" title="Edit section: Diastereomers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Stereoisomers that are not enantiomers are called <a href="/wiki/Diastereomer" title="Diastereomer">diastereomers</a>. Some diastereomers may contain <a href="/wiki/Chiral_center" class="mw-redirect" title="Chiral center">chiral centers</a>, and some may not.<sup id="cite_ref-Eliel_12-0" class="reference"><a href="#cite_note-Eliel-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Cis-trans_isomerism">Cis-trans isomerism</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=8" title="Edit section: Cis-trans isomerism"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A double bond between two carbon atoms forces the remaining four bonds (if they are single) to lie on the same plane, perpendicular to the plane of the bond as defined by its <a href="/wiki/%CE%A0_bond" class="mw-redirect" title="Π bond">π orbital</a>. If the two bonds on each carbon connect to different atoms, two distinct conformations are possible that differ from each other by a twist of 180 degrees of one of the carbons about the double bond. </p><p>The classical example is dichloroethene <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {C2H2Cl2}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>Cl</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {C2H2Cl2}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/367dd6b1bb00f7135a2a4ce25db1f3b87474e138" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:8.909ex; height:2.843ex;" alt="{\displaystyle {\ce {C2H2Cl2}}}" /></span>, specifically the structural isomer <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {Cl-HC=CH-Cl}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>Cl</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>HC</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>=</mo> </mrow> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>Cl</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {Cl-HC=CH-Cl}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7e1d7d32bdb46b333c1cbef980af8ef605e6dd03" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:16.917ex; height:2.343ex;" alt="{\displaystyle {\ce {Cl-HC=CH-Cl}}}" /></span> that has one chlorine bonded to each carbon. It has two conformational isomers, with the two chlorines on the same side or on opposite sides of the double bond's plane. They are traditionally called <i>cis</i> (from Latin meaning "on this side of") and <i>trans</i> ("on the other side of"), respectively, or <i>Z</i> and <i>E</i> in the <a href="/wiki/IUPAC" class="mw-redirect" title="IUPAC">IUPAC</a> recommended nomenclature. Conversion between these two forms usually requires temporarily breaking bonds (or turning the double bond into a single bond), so the two are considered different configurations of the molecule. </p><p>More generally, <a href="/wiki/Cis%E2%80%93trans_isomerism" title="Cis–trans isomerism"><i>cis</i>–<i>trans</i> isomerism</a> (formerly called "geometric isomerism") occurs in molecules where the relative orientation of two distinguishable functional groups is restricted by a somewhat rigid framework of other atoms.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p>For example, in the cyclic alcohol <a href="/wiki/Inositol" title="Inositol">inositol</a> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {(CHOH)6}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">(</mo> <mtext>CHOH</mtext> <mo stretchy="false">)</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>6</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {(CHOH)6}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d8ed84eecaa77b0cdea3c27a7c3f4383126708e6" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:9.836ex; height:3.009ex;" alt="{\displaystyle {\ce {(CHOH)6}}}" /></span> (a six-fold alcohol of cyclohexane), the six-carbon cyclic backbone largely prevents the hydroxyl <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {-OH}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>OH</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {-OH}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a5328d8e0b5cd0c3639195893ea742237999a572" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:5.359ex; height:2.343ex;" alt="{\displaystyle {\ce {-OH}}}" /></span> and the hydrogen <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {-H}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mtext>H</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {-H}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/51fae9b82d7452dc1dbace378bf553606055c9a5" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.505ex; width:3.551ex; height:2.343ex;" alt="{\displaystyle {\ce {-H}}}" /></span> on each carbon from switching places. Therefore, one has different configurational isomers depending on whether each hydroxyl is on "this side" or "the other side" of the ring's mean plane. Discounting isomers that are equivalent under rotations, there are nine isomers that differ by this criterion, and behave as different stable substances (two of them being enantiomers of each other). The most common one in nature (<i>myo</i>-inositol) has the hydroxyls on carbons 1, 2, 3 and 5 on the same side of that plane, and can therefore be called <i>cis</i>-1,2,3,5-<i>trans</i>-4,6-cyclohexanehexol. And each of these <i>cis</i>-<i>trans</i> isomers can possibly have stable "chair" or "boat" conformations (although the barriers between these are significantly lower than those between different <i>cis</i>-<i>trans</i> isomers). </p> <figure class="mw-halign-right skin-invert-image" typeof="mw:File/Thumb"><a href="/wiki/File:Cisplatin_and_transplatin.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/5/57/Cisplatin_and_transplatin.svg/320px-Cisplatin_and_transplatin.svg.png" decoding="async" width="320" height="144" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/57/Cisplatin_and_transplatin.svg/480px-Cisplatin_and_transplatin.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/5/57/Cisplatin_and_transplatin.svg/640px-Cisplatin_and_transplatin.svg.png 2x" data-file-width="275" data-file-height="124" /></a><figcaption>The two isomeric complexes, <a href="/wiki/Cisplatin" title="Cisplatin">cisplatin</a> and <a href="/wiki/Transplatin" title="Transplatin">transplatin</a>, are examples of square planar MX<sub>2</sub>Y<sub>2</sub> molecules with M = Pt.</figcaption></figure> <p><a href="/wiki/Coordination_complex#Cis–trans_isomerism_and_facial–meridional_isomerism" title="Coordination complex"><i>Cis</i> and <i>trans</i> isomers</a> also occur in inorganic <a href="/wiki/Coordination_compound" class="mw-redirect" title="Coordination compound">coordination compounds</a>, such as <a href="/wiki/Square_planar_molecular_geometry" title="Square planar molecular geometry">square planar</a> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {MX2Y2}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>MX</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>Y</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {MX2Y2}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/89d6b04beb0aff0255d060dcfe82b94e7eb17930" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:7.726ex; height:2.843ex;" alt="{\displaystyle {\ce {MX2Y2}}}" /></span> complexes and <a href="/wiki/Octahedral_molecular_geometry" title="Octahedral molecular geometry">octahedral</a> <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {MX4Y2}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>MX</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>Y</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {MX4Y2}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/fbc05157241b10a16716bf12ad33392324c6de05" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:7.726ex; height:2.843ex;" alt="{\displaystyle {\ce {MX4Y2}}}" /></span> complexes. </p><p>For more complex organic molecules, the <i>cis</i> and <i>trans</i> labels can be ambiguous. In such cases, a more precise labeling scheme is employed based on the <a href="/wiki/Cahn-Ingold-Prelog_priority_rules" class="mw-redirect" title="Cahn-Ingold-Prelog priority rules">Cahn-Ingold-Prelog priority rules</a>.<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><sup id="cite_ref-Eliel_12-1" class="reference"><a href="#cite_note-Eliel-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p><p><br /> </p> <div class="mw-heading mw-heading2"><h2 id="Isotopes_and_spin">Isotopes and spin</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=9" title="Edit section: Isotopes and spin"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Isotopomers">Isotopomers</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=10" title="Edit section: Isotopomers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Different isotopes of the same element can be considered as different kinds of atoms when enumerating isomers of a molecule or ion. The replacement of one or more atoms by their isotopes can create multiple structural isomers and/or stereoisomers from a single isomer. </p><p>For example, replacing two atoms of common <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a> (<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {^1 H}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mmultiscripts> <mtext>H</mtext> <none></none> <none></none> <mprescripts></mprescripts> <none></none> <mn>1</mn> </mmultiscripts> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {^1 H}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f14898bb2934c97f9d6fb37be91eeef9160dde7d" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.739ex; height:2.676ex;" alt="{\displaystyle {\ce {^1 H}}}" /></span>) by <a href="/wiki/Deuterium" title="Deuterium">deuterium</a> (<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {^2 H}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mmultiscripts> <mtext>H</mtext> <none></none> <none></none> <mprescripts></mprescripts> <none></none> <mn>2</mn> </mmultiscripts> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {^2 H}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/059d80356842d64716ca8b5dded6cb0574a06b5f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.739ex; height:2.676ex;" alt="{\displaystyle {\ce {^2 H}}}" /></span>, or <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {D}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>D</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {D}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a4e215677e3f79b142b9b46e9d2f5d5a153b3b69" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.776ex; height:2.176ex;" alt="{\displaystyle {\ce {D}}}" /></span>) on an <a href="/wiki/Ethane" title="Ethane">ethane</a> molecule yields two distinct structural isomers, depending on whether the substitutions are both on the same carbon (1,1-dideuteroethane, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {HD2C-CH3}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>HD</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {HD2C-CH3}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c7155c920e0b89388c5fff3b60b12cbc315f54fc" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:12.535ex; height:2.843ex;" alt="{\displaystyle {\ce {HD2C-CH3}}}" /></span>) or one on each carbon (1,2-dideuteroethane, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {DH2C-CDH2}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>DH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <msubsup> <mtext>CDH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {DH2C-CDH2}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6c0c0b067ab6aec66bd5efd83f67805e7819b749" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:14.31ex; height:2.843ex;" alt="{\displaystyle {\ce {DH2C-CDH2}}}" /></span>); as if the substituent was <a href="/wiki/Chlorine" title="Chlorine">chlorine</a> instead of deuterium. The two molecules do not interconvert easily and have different properties, such as their <a href="/wiki/Microwave_spectroscopy" title="Microwave spectroscopy">microwave spectrum</a>.<sup id="cite_ref-hiro2012_15-0" class="reference"><a href="#cite_note-hiro2012-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p><p>Another example would be substituting one atom of deuterium for one of the hydrogens in <a href="/wiki/Chlorofluoromethane" title="Chlorofluoromethane">chlorofluoromethane</a> (<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {CH2ClF}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>ClF</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {CH2ClF}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c2ca770cb7e661151541f802b072d03d313d86fe" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:8.318ex; height:2.843ex;" alt="{\displaystyle {\ce {CH2ClF}}}" /></span>). While the original molecule is not chiral and has a single isomer, the substitution creates a pair of chiral enantiomers of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {CHDClF}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>CHDClF</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {CHDClF}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/adfaf0f8f4fd3e9d99965c41d84c19725ab5063e" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:9.04ex; height:2.176ex;" alt="{\displaystyle {\ce {CHDClF}}}" /></span>, which could be distinguished (at least in theory) by their optical activity.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </p><p>When two isomers would be identical if all isotopes of each element were replaced by a single isotope, they are described as <a href="/wiki/Isotopomer" title="Isotopomer">isotopomers</a> or isotopic isomers.<sup id="cite_ref-Seeman_17-0" class="reference"><a href="#cite_note-Seeman-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> In the above two examples if all <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {D}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>D</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {D}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a4e215677e3f79b142b9b46e9d2f5d5a153b3b69" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.776ex; height:2.176ex;" alt="{\displaystyle {\ce {D}}}" /></span> were replaced by <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {H}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>H</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {H}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/651c6a42285fecf133dd3f1671440f813e2ecd6f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.743ex; height:2.176ex;" alt="{\displaystyle {\ce {H}}}" /></span>, the two dideuteroethanes would both become ethane and the two deuterochlorofluoromethanes would both become <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {CH2ClF}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>ClF</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {CH2ClF}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c2ca770cb7e661151541f802b072d03d313d86fe" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:8.318ex; height:2.843ex;" alt="{\displaystyle {\ce {CH2ClF}}}" /></span>. </p><p>The concept of isotopomers is different from <a href="/wiki/Isotopologue" title="Isotopologue">isotopologs</a> or isotopic homologs, which differ in their isotopic composition.<sup id="cite_ref-Seeman_17-1" class="reference"><a href="#cite_note-Seeman-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> For example, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {C2H5D}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>5</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>D</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {C2H5D}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/34c47a66e1c562f92821def524cf617c65ec3692" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:7.305ex; height:2.843ex;" alt="{\displaystyle {\ce {C2H5D}}}" /></span> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {C2H4D2}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>D</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {C2H4D2}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3a063eb275e2950a611768d688ced2e3caa86fed" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:8.36ex; height:2.843ex;" alt="{\displaystyle {\ce {C2H4D2}}}" /></span> are isotopologues and not isotopomers, and are therefore not isomers of each other. </p> <div class="mw-heading mw-heading3"><h3 id="Spin_isomers">Spin isomers</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=11" title="Edit section: Spin isomers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Another type of isomerism based on nuclear properties is <a href="/wiki/Spin_isomers_of_hydrogen" title="Spin isomers of hydrogen">spin isomerism</a>, where molecules differ only in the relative <a href="/wiki/Spin_quantum_number" title="Spin quantum number">spin magnetic quantum numbers</a> m<sub>s</sub> of the constituent atomic nuclei. This phenomenon is significant for molecular hydrogen, which can be partially separated into two long-lived states described as spin isomers<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> or nuclear spin isomers:<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> parahydrogen, with the spins of the two nuclei pointing in opposite directions, and orthohydrogen, where the spins point in the same direction. </p> <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=Isomer&action=edit&section=12" title="Edit section: Applications"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Isomers having distinct biological properties are common; for example, the placement of <a href="/wiki/Methyl_group" title="Methyl group">methyl groups</a>. In substituted <a href="/wiki/Xanthine" title="Xanthine">xanthines</a>, <a href="/wiki/Theobromine" title="Theobromine">theobromine</a>, found in chocolate, is a <a href="/wiki/Vasodilator" class="mw-redirect" title="Vasodilator">vasodilator</a> with some effects in common with <a href="/wiki/Caffeine" title="Caffeine">caffeine</a>; but, if one of the two methyl groups is moved to a different position on the two-ring core, the isomer is <a href="/wiki/Theophylline" title="Theophylline">theophylline</a>, which has a variety of effects, including <a href="/wiki/Bronchodilator" title="Bronchodilator">bronchodilation</a> and <a href="/wiki/Anti-inflammatory" title="Anti-inflammatory">anti-inflammatory</a> action. Another example of this occurs in the <a href="/wiki/Phenethylamine" title="Phenethylamine">phenethylamine</a>-based stimulant drugs. <a href="/wiki/Phentermine" title="Phentermine">Phentermine</a> is a <a href="/wiki/Chirality_(chemistry)" title="Chirality (chemistry)">non-chiral</a> compound with a weaker effect than that of <a href="/wiki/Amphetamine" title="Amphetamine">amphetamine</a>. It is used as an appetite-reducing medication and has mild or no stimulant properties. However, an alternate atomic arrangement gives <a href="/wiki/Dextromethamphetamine" class="mw-redirect" title="Dextromethamphetamine">dextromethamphetamine</a>, which is a stronger stimulant than amphetamine. </p><p>In <a href="/wiki/Medicinal_chemistry" title="Medicinal chemistry">medicinal chemistry</a> and biochemistry, <a href="/wiki/Enantiomer" title="Enantiomer">enantiomers</a> are a special concern because they may possess distinct <a href="/wiki/Biological_activity" title="Biological activity">biological activity</a>. Many preparative procedures afford a mixture of equal amounts of both enantiomeric forms. In some cases, the enantiomers are separated by <a href="/wiki/Chromatography" title="Chromatography">chromatography</a> using chiral stationary phases. They may also be separated through the formation of <a href="/wiki/Diastereomeric_crystallization" class="mw-redirect" title="Diastereomeric crystallization">diastereomeric salts</a>. In other cases, <a href="/wiki/Enantioselective_synthesis" title="Enantioselective synthesis">enantioselective synthesis</a> have been developed. </p><p>As an inorganic example, <a href="/wiki/Cisplatin" title="Cisplatin">cisplatin</a> (see structure above) is an important drug used in cancer chemotherapy, whereas the trans isomer (transplatin) has no useful pharmacological activity. </p> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Isomer&action=edit&section=13" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Isomerism was first observed in 1827, when <a href="/wiki/Friedrich_W%C3%B6hler" title="Friedrich Wöhler">Friedrich Wöhler</a> prepared <a href="/wiki/Silver_cyanate" title="Silver cyanate">silver cyanate</a> and discovered that, although its elemental composition of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {AgCNO}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>AgCNO</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {AgCNO}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/1eb8fad7c6026fbf4b6d49e450e0e474b4db2a3a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:8.135ex; height:2.509ex;" alt="{\displaystyle {\ce {AgCNO}}}" /></span> was identical to <a href="/wiki/Silver_fulminate" title="Silver fulminate">silver fulminate</a> (prepared by <a href="/wiki/Justus_von_Liebig" title="Justus von Liebig">Justus von Liebig</a> the previous year),<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> its properties were distinct. This finding challenged the prevailing chemical understanding of the time, which held that <a href="/wiki/Chemical_compound" title="Chemical compound">chemical compounds</a> could be distinct only when their elemental compositions differ. (We now know that the bonding structures of <a href="/wiki/Fulminate" title="Fulminate">fulminate</a> and <a href="/wiki/Cyanate" title="Cyanate">cyanate</a> can be approximately described as <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {O- N+}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msup> <mtext>O</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> </msup> <msup> <mtext>N</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>+</mo> </mrow> </msup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {O- N+}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/585139f3255f720fd32a4df98b5e6819285b68c7" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:6.573ex; height:2.509ex;" alt="{\displaystyle {\ce {O- N+}}}" /></span>≡<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {C-}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> </msup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {C-}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2dea6afbf24ec5264cf0caa2b7d9fdd8f40b0ccb" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:3.189ex; height:2.509ex;" alt="{\displaystyle {\ce {C-}}}" /></span> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {O=C=N-}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>O</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>=</mo> </mrow> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>=</mo> </mrow> <msup> <mtext>N</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> </msup> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {O=C=N-}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d31a198841e77120b4a09ee505f2b87b4d03aa98" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:10.356ex; height:2.509ex;" alt="{\displaystyle {\ce {O=C=N-}}}" /></span>, respectively.) </p><p>Additional examples were found in succeeding years, such as Wöhler's 1828 discovery that <a href="/wiki/Urea" title="Urea">urea</a> has the same atomic composition (<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {CH4N2O}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mtext>CH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <msubsup> <mtext>N</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>O</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {CH4N2O}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/94148b7489da7e1cf51c51c2ef5b47cc11444208" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:9.081ex; height:2.843ex;" alt="{\displaystyle {\ce {CH4N2O}}}" /></span>) as the chemically distinct <a href="/wiki/Ammonium_cyanate" title="Ammonium cyanate">ammonium cyanate</a>. (Their structures are now known to be <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {(H2N-)2C=O}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msubsup> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">(</mo> <msubsup> <mtext>H</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>N</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> <mo stretchy="false">)</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mspace width="0pt" height="0pt" depth=".2em"></mspace> </mrow> </msubsup> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>=</mo> </mrow> <mtext>O</mtext> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {(H2N-)2C=O}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/4855aa3ee05f54745c3fe82fb3139e4d8a447fcc" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:14.506ex; height:3.009ex;" alt="{\displaystyle {\ce {(H2N-)2C=O}}}" /></span> and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\ce {[NH+4][O=C=N^{-}]}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">[</mo> <msubsup> <mtext>NH</mtext> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>+</mo> </mrow> </msubsup> <mo stretchy="false">]</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">[</mo> <mtext>O</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>=</mo> </mrow> <mtext>C</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>=</mo> </mrow> <msup> <mtext>N</mtext> <mrow class="MJX-TeXAtom-ORD"> <mo>−</mo> </mrow> </msup> <mo stretchy="false">]</mo> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\ce {[NH+4][O=C=N^{-}]}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6d88ac58af5dbab726d06cd37724e55e9cac30ba" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:17.941ex; height:3.176ex;" alt="{\displaystyle {\ce {[NH+4][O=C=N^{-}]}}}" /></span>, respectively.) In 1830 <a href="/wiki/J%C3%B6ns_Jacob_Berzelius" title="Jöns Jacob Berzelius">Jöns Jacob Berzelius</a> introduced the term <i>isomerism</i> to describe the phenomenon.<sup id="cite_ref-berz1830_4-1" class="reference"><a href="#cite_note-berz1830-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-berz1831a_21-0" class="reference"><a href="#cite_note-berz1831a-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-berz1831b_22-0" class="reference"><a href="#cite_note-berz1831b-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p><p>In 1848, <a href="/wiki/Louis_Pasteur" title="Louis Pasteur">Louis Pasteur</a> observed that <a href="/wiki/Tartaric_acid" title="Tartaric acid">tartaric acid</a> crystals came into two kinds of shapes that were mirror images of each other. Separating the crystals by hand, he obtained two version of tartaric acid, each of which would crystallize in only one of the two shapes, and rotated the plane of polarized light to the same degree but in opposite directions.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> In 1860, Pasteur explicitly hypothesized that the molecules of isomers might have the same composition but different arrangements of their atoms.<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<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=Isomer&action=edit&section=14" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 30em;"> <ul><li><a href="/wiki/Allotropy" title="Allotropy">Allotropy</a> (of elements)</li> <li><a href="/wiki/Chirality_(chemistry)" title="Chirality (chemistry)">Chirality (chemistry)</a></li> <li><a href="/wiki/Cis-trans_isomerism" class="mw-redirect" title="Cis-trans isomerism">Cis-trans isomerism</a></li> <li><a href="/wiki/Cyclohexane_conformation" title="Cyclohexane conformation">Cyclohexane conformation</a></li> <li><a href="/wiki/Descriptor_(chemistry)" title="Descriptor (chemistry)">Descriptor (chemistry)</a></li> <li><a href="/wiki/Electromerism" title="Electromerism">Electromerism</a></li> <li><a href="/wiki/Isomerization" title="Isomerization">Isomerization</a></li> <li><a href="/wiki/Merosity" title="Merosity">Isomery (botany)</a></li> <li><a href="/wiki/Ligand_isomerism" title="Ligand isomerism">Ligand isomerism</a></li> <li><a href="/wiki/Nuclear_isomer" title="Nuclear isomer">Nuclear isomer</a></li> <li><a href="/wiki/Stereocenter" title="Stereocenter">Stereocenter</a></li> <li><a href="/wiki/Structural_isomerism" class="mw-redirect" title="Structural isomerism">Structural isomerism</a></li> <li><a href="/wiki/Tautomer" title="Tautomer">Tautomer</a></li> <li><a href="/wiki/Vitamer" title="Vitamer">Vitamer</a></li></ul> </div> <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=Isomer&action=edit&section=15" 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"><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><cite id="CITEREFPetrucciHarwoodHerring2002" class="citation book cs1">Petrucci, Ralph H.; Harwood, William S.; Herring, F. Geoffrey (2002). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/generalchemistry00hill"><i>General chemistry: principles and modern applications</i></a></span> (8th ed.). Upper Saddle River, N.J: Prentice Hall. p. 91]. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-13-014329-7" title="Special:BookSources/978-0-13-014329-7"><bdi>978-0-13-014329-7</bdi></a>. <a href="/wiki/LCCN_(identifier)" class="mw-redirect" title="LCCN (identifier)">LCCN</a> <a rel="nofollow" class="external text" href="https://lccn.loc.gov/2001032331">2001032331</a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/46872308">46872308</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=General+chemistry%3A+principles+and+modern+applications&rft.place=Upper+Saddle+River%2C+N.J&rft.pages=91&rft.edition=8th&rft.pub=Prentice+Hall&rft.date=2002&rft_id=info%3Aoclcnum%2F46872308&rft_id=info%3Alccn%2F2001032331&rft.isbn=978-0-13-014329-7&rft.aulast=Petrucci&rft.aufirst=Ralph+H.&rft.au=Harwood%2C+William+S.&rft.au=Herring%2C+F.+Geoffrey&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fgeneralchemistry00hill&rfr_id=info%3Asid%2Fen.wikipedia.org%3AIsomer" class="Z3988"></span></span> </li> <li id="cite_note-MW.isomer-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-MW.isomer_2-0">^</a></b></span> <span class="reference-text">Merriam-Webster: <a rel="nofollow" class="external text" href="https://www.merriam-webster.com/dictionary/isomer">"isomer"</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20201021040204/https://www.merriam-webster.com/dictionary/isomer">Archived</a> 21 October 2020 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> online dictionary entry. Accessed on 2020-08-26</span> </li> <li id="cite_note-MW.isomeric-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-MW.isomeric_3-0">^</a></b></span> <span class="reference-text">Merriam-Webster: <a rel="nofollow" class="external text" href="https://www.merriam-webster.com/dictionary/isomeric">"isomeric"</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20201026100040/https://www.merriam-webster.com/dictionary/isomeric">Archived</a> 26 October 2020 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a> online dictionary entry. Accessed on 2020-08-26</span> </li> <li id="cite_note-berz1830-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-berz1830_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-berz1830_4-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Jac. Berzelius (1830): "<a rel="nofollow" class="external text" href="https://books.google.com/books?id=2OY4AAAAMAAJ&pg=RA1-PA70">Om sammansättningen af vinsyra och drufsyra (John's säure aus den Voghesen), om blyoxidens atomvigt, samt allmänna anmärkningar om sådana kroppar som hafva lika sammansättning, men skiljaktiga egenskaper</a>" ("On the composition of tartaric acid and racemic acid (John's acid of the Vosges), on the molecular weight of lead oxide, together with general observations on those bodies that have the same composition but distinct properties"). <i>Kongliga Svenska Vetenskaps Academiens Handling</i> (<i>Transactions of the Royal Swedish Science Academy</i>), volume 49, pages 49–80</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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSmith2010" class="citation book cs1">Smith, Janice Gorzynski (2010). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=oGz9XwAACAAJ&pg=PA450"><i>General, Organic and Biological Chemistry</i></a> (1st ed.). McGraw-Hill. p. 450. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-07-302657-2" title="Special:BookSources/978-0-07-302657-2"><bdi>978-0-07-302657-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=General%2C+Organic+and+Biological+Chemistry&rft.pages=450&rft.edition=1st&rft.pub=McGraw-Hill&rft.date=2010&rft.isbn=978-0-07-302657-2&rft.aulast=Smith&rft.aufirst=Janice+Gorzynski&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DoGz9XwAACAAJ%26pg%3DPA450&rfr_id=info%3Asid%2Fen.wikipedia.org%3AIsomer" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation journal cs1"><a rel="nofollow" class="external text" href="http://goldbook.iupac.org/html/T/T06252.html">"tautomerism"</a>. <i>IUPAC Gold Book</i>. IUPAC. 2014. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1351%2Fgoldbook.T06252">10.1351/goldbook.T06252</a></span>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20190406145801/http://goldbook.iupac.org/html/T/T06252.html">Archived</a> from the original on 6 April 2019<span class="reference-accessdate">. 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Berzelius (1831): "<a rel="nofollow" class="external text" href="https://books.google.com/books?id=mOQ3AAAAMAAJ&pg=PA136">Composition de l'acide tartarique et de l'acide racémique (traubensäure); poids atomique de l'oxide de plomb, et remarques générals sur les corps qui ont la même composition, et possèdent des proprietés différentes</a>". <i>Annales de Chimie et de Physique</i>, volume 46, pages 113–147.</span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFEsteban,_Soledad2008" class="citation journal cs1">Esteban, Soledad (2008). <a rel="nofollow" class="external text" href="http://jchemed.chem.wisc.edu/Journal/Issues/2008/Sep/abs1201.html">"Liebig–Wöhler Controversy and the Concept of Isomerism"</a>. <i>J. Chem. Educ</i>. <b>85</b> (9): 1201. <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/2008JChEd..85.1201E">2008JChEd..85.1201E</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1021%2Fed085p1201">10.1021/ed085p1201</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20080823172737/http://jchemed.chem.wisc.edu/Journal/Issues/2008/Sep/abs1201.html">Archived</a> from the original on 23 August 2008<span class="reference-accessdate">. Retrieved <span class="nowrap">9 September</span> 2008</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=J.+Chem.+Educ.&rft.atitle=Liebig%E2%80%93W%C3%B6hler+Controversy+and+the+Concept+of+Isomerism&rft.volume=85&rft.issue=9&rft.pages=1201&rft.date=2008&rft_id=info%3Adoi%2F10.1021%2Fed085p1201&rft_id=info%3Abibcode%2F2008JChEd..85.1201E&rft.au=Esteban%2C+Soledad&rft_id=http%3A%2F%2Fjchemed.chem.wisc.edu%2FJournal%2FIssues%2F2008%2FSep%2Fabs1201.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AIsomer" class="Z3988"></span></span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text">L. Pasteur (1848) "Mémoire sur la relation qui peut exister entre la forme cristalline et la composition chimique, et sur la cause de la polarisation rotatoire" (Memoir on the relationship which can exist between crystalline form and chemical composition, and on the cause of rotary polarization)," <i>Comptes rendus de l'Académie des sciences</i> (Paris), vol. 26, pages 535–538.</span> </li> <li id="cite_note-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-25">^</a></b></span> <span class="reference-text">L. Pasteur (1848) <a rel="nofollow" class="external text" href="https://books.google.com/books?id=gJ45AAAAcAAJ&pg=PA442">"Sur les relations qui peuvent exister entre la forme cristalline, la composition chimique et le sens de la polarisation rotatoire"</a> ("On the relations that can exist between crystalline form, chemical composition, and the sense of rotary polarization"), <i>Annales de Chimie et de Physique</i>, 3rd series, volume 24, issue 6, pages 442–459.</span> </li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text"><a href="#refPullman1998">Pullman (1998). <i>The Atom in the History of Human Thought</i>, p. 230</a></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=Isomer&action=edit&section=16" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Wikiquote-logo.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikiquote-logo.svg/34px-Wikiquote-logo.svg.png" decoding="async" width="34" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikiquote-logo.svg/51px-Wikiquote-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Wikiquote-logo.svg/68px-Wikiquote-logo.svg.png 2x" data-file-width="300" data-file-height="355" /></a></span></div> <div class="side-box-text plainlist">Wikiquote has quotations related to <i><b><a href="https://en.wikiquote.org/wiki/Special:Search/Isomer" class="extiw" title="q:Special:Search/Isomer">Isomer</a></b></i>.</div></div> </div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1235681985" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1237033735" /><div class="side-box side-box-right plainlinks sistersitebox"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1126788409" /> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Commons-logo.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/40px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/60px-Commons-logo.svg.png 1.5x" data-file-width="1024" data-file-height="1376" /></a></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; 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Inc.","logo":{"@type":"ImageObject","url":"https:\/\/www.wikimedia.org\/static\/images\/wmf-hor-googpub.png"}},"datePublished":"2001-09-01T22:56:42Z","dateModified":"2025-02-26T10:52:44Z","image":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/4\/4b\/IsomerOverview.svg","headline":"molecule with identical atomic composition as another, but with different structures or orientations"}</script> </body> </html>