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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head profile="http://gmpg.org/xfn/1"> <title>Computational Organic Chemistry » Ozonolysis</title> <meta name="google-site-verification" content="g1Myv4tUVAmqRbwZeBi7IPuSZpP64RWjVJ6itIoouCo"> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <style type="text/css" media="screen">@import url( /blog/wp-content/themes/comporg/style.css);</style> <link rel="stylesheet" id="wp-block-library-css" href="/blog/wp-includes/css/dist/block-library/style.min.css?ver=5.6.1" type="text/css" media="all"> <link rel="canonical" href="/blog/archives/66"> <script type="text/javascript">  </script> </head> <body> <div id="header"> <div id="header_img"></div> </div> <div id="link_section"> <div style="float:left"> <a href="/blog/about">About this Blog</a> | <a href="/">Book Homepage</a> | <a href="http://www.wiley.com/WileyCDA/WileyTitle/productCd-0471713422.html">Purchase the Book</a> </div> </div> <div id="after_links"></div> <div id="content"> <div id="main"> <div class="box"> <h2><a href="/blog/archives/66" rel="bookmark" title="Permanent Link: Ozonolysis">Ozonolysis</a></h2> <div class="post-content"> <p>The composite methods (exemplified by the <i>G</i>aussian-n methods, the <i>W</i>eizmann-n methods and CNS-Q methods) are popularly held to be perhaps the best (if not the most straightforward and mechanical) procedures for obtaining accurate energetics. Errors are generally thought to be in the 1-2 kcal mol<sup>-1</sup> range – quite suitable for comparisons with experiment. The recent study of the 1,3-dipolar cycloaddition of ozone with ethene or ethyne offers serious food for thought about considering these composite methods as simple “black-box” solutions towards obtaining good results.<br> Wheeler, Ess, and Houk have examined the cycloaddition of ozone with ethyne (Reaction 1) and ethane (Reaction 2) with a variety of different computational techniques.<a href="#ozoneRef1"><sup>1</sup></a> Shown in Figure 1 are the CCSD(T)/cc-pVTZ optimized geometries of the pre-complex, transition state and product for both reactions. One of the potential challenges of these reactions is that ozone has appreciable radical character which is also likely to be true in the pre-complex and transition state but the product should have little to no radical character.</p> <table border="0" cellspacing="0" cellpadding="3" align="center"> <tr> <td> <p><img src="/blog/wp-content/ozone1.gif"></p> </td> <td> <p>Reaction 1</p> </td> </tr> <tr> <td> <p><img src="/blog/wp-content/ozone2.gif"></p> </td> <td> <p>Reaction 2</p> </td> </tr> </table> <table border="0" cellspacing="0" cellpadding="3" align="center"> <tr> <td colspan="3"> <p align="center">Reaction 1</p> </td> </tr> <tr> <td> <p></p> <div class="jmol" id="ozc1" align="center"> <a onclick="return false"><br> <img src="/blog/wp-content/ozone-c1.gif" onclick="insertJmol('ozc1',200,200,'ozone-c1.xyz')"></a> </div> <p>Precomplex</p> </td> <td> <p></p> <div class="jmol" id="ozt1" align="center"> <a onclick="return false"><br> <img src="/blog/wp-content/ozone-t1.gif" onclick="insertJmol('ozt1',200,200,'ozone-t1.xyz')"></a> </div> <p>TS</p> </td> <td> <p></p> <div class="jmol" id="ozp1" align="center"> <a onclick="return false"><br> <img src="/blog/wp-content/ozone-p1.gif" onclick="insertJmol('ozp1',200,200,'ozone-p1.xyz')"></a> </div> <p>Product</p> </td> </tr> <tr> <td colspan="3"> <p align="center">Reaction 2</p> </td> </tr> <tr> <td> <p></p> <div class="jmol" id="ozc2" align="center"> <a onclick="return false"><br> <img src="/blog/wp-content/ozone-c2.gif" onclick="insertJmol('ozc2',200,200,'ozone-c2.xyz')"></a> </div> <p>Precomplex</p> </td> <td> <p></p> <div class="jmol" id="ozt2" align="center"> <a onclick="return false"><br> <img src="/blog/wp-content/ozone-t2.gif" onclick="insertJmol('ozt2',200,200,'ozone-t2.xyz')"></a> </div> <p>TS</p> </td> <td> <p></p> <div class="jmol" id="ozp2" align="center"> <a onclick="return false"><br> <img src="/blog/wp-content/ozone-p2.gif" onclick="insertJmol('ozp2',200,200,'ozone-p2.xyz')"></a> </div> <p>Product</p> </td> </tr> </table> <p>The relative enthalphies (0K) of the complex, TS and product were computed using a number of different composite methods. The CBS-QB3, G3, G3B3, G3MP2B3 and G4<a href="#ozoneRef2"><sup>2,3</sup></a> results are listed in Table 1 for both reactions. All of these methods claim a small error – perhaps 1-2 kcal mol<sup>-1</sup>. The <i>G</i>aussian-n methods nicely cluster for the reaction energy for both reactions, while CBS-QB3 predicts both reactions are more exothermic. (The same is also true of CBS-APNO.) The <i>G</i>-n methods indicate that the precomplex is essentially unbound. More concerning is the spread in the enthalpy values of the reaction barrier: the <i>G</i>-n methods predict a barrier that ranges over 5 kcal mol<sup>-1</sup>.</p> <p align="center"><b>Table 1</b>. Relative enthalpies (kcal mol<sup>-1</sup>) of the critical points for Reactions 1 and 2.<a href="#ozoneRef1"><sup>1</sup></a></p> <table border="0" cellspacing="0" cellpadding="3" align="center"> <tr> <td colspan="7"> <hr> </td> </tr> <tr> <td> <p> </p> </td> <td colspan="3"> <p align="center">Reaction 1</p> </td> <td colspan="3"> <p align="center">Reaction 2</p> </td> </tr> <tr> <td> <p> </p> </td> <td> <p align="center">precomplex</p> </td> <td> <p align="center">TS</p> </td> <td> <p align="center">product</p> </td> <td> <p align="center">precomplex</p> </td> <td> <p align="center">TS</p> </td> <td> <p align="center">product</p> </td> </tr> <tr> <td> <p>CBS-QB3</p> </td> <td> <p align="center">-1.2</p> </td> <td> <p align="center">4.4</p> </td> <td> <p align="center">-60.8</p> </td> <td> <p align="center">-0.6</p> </td> <td> <p align="center">0.7</p> </td> <td> <p align="center">-54.2</p> </td> </tr> <tr> <td> <p>G3</p> </td> <td> <p align="center">0.3</p> </td> <td> <p align="center">12.7</p> </td> <td> <p align="center">-57.7</p> </td> <td> <p align="center">1.6</p> </td> <td> <p align="center">0.5</p> </td> <td> <p align="center">-50.6</p> </td> </tr> <tr> <td> <p>G3B3</p> </td> <td> <p align="center">-0.8</p> </td> <td> <p align="center">7.8</p> </td> <td> <p align="center">-57.3</p> </td> <td> <p align="center">0.0</p> </td> <td> <p align="center">3.0</p> </td> <td> <p align="center">-50.8</p> </td> </tr> <tr> <td> <p>G3MP2B3</p> </td> <td> <p align="center">-0.7</p> </td> <td> <p align="center">7.3</p> </td> <td> <p align="center">-57.3</p> </td> <td> <p align="center">0.2</p> </td> <td> <p align="center">3.0</p> </td> <td> <p align="center">-50.3</p> </td> </tr> <tr> <td> <p>G4</p> </td> <td> <p align="center">-0.8</p> </td> <td> <p align="center">9.0</p> </td> <td> <p align="center">-57.4</p> </td> <td> <p align="center">-0.3</p> </td> <td> <p align="center">4.6</p> </td> <td> <p align="center">-50.4</p> </td> </tr> <tr> <td> <p>Focal point</p> </td> <td> <p align="center">-1.1</p> </td> <td> <p align="center">9.4</p> </td> <td> <p align="center">-57.9</p> </td> <td> <p align="center">-1.2</p> </td> <td> <p align="center">5.3</p> </td> <td> <p align="center">-50.9</p> </td> </tr> <tr> <td colspan="7"> <hr> </td> </tr> </table> <p>So what is the correct barrier height? A focal point extrapolation procedure was then performed. This seeks to extrapolate to infinite basis set and estimate the effects of correlation through CCSDT(Q) and includes corrections for the Born-Oppenheimer approximation and special relativistic effects. The focal point results are also shown in Table 1. The new G4 composite method gives enthalpies in very nice agreement with those obtained with the much more expensive focal point procedure. However, the other composite methods fair much worse, especially for the activation barrier.<br> The convergence of the focal point method for the reaction energy is slow, leading to a large error bar of 2 kcal mol<sup>-1</sup>. This appears to relate to the radical character difference between the reactant and product. The convergence for the activation barrier is much better (an error of only 0.2 kcal mol<sup>-1</sup>) and here the comparison is between reactant and TS which have similar radical character.<br> Perhaps the most discouraging aspect of this study is that the relative energy predicted using the highest computational component of the composite method – so, CCSD(T)/6-31+G* for the CBS-QB3 method and QCISD(T)/6-31G(d) for the G3 methods – are <i>more accurate than the composite method itself</i>. But, the reasonable performance of the new <i>G</i>4 method<a href="#ozoneRef2"><sup>2,3</sup></a> does offer some glimmer of hope here.</p> <h3>References</h3> <p><a name="ozoneRef1"></a></p> <p>(1) Wheeler, S. E.; Ess, D. H.; Houk, K. N., "Thinking<br> Out of the Black Box: Accurate Barrier Heights of 1,3-Dipolar Cycloadditions of Ozone with Acetylene and Ethylene," <i>J. Phys. Chem. A,</i> <b>2008</b>, <i>112</i>, 1798-1807, DOI: <a href="http://dx.doi.org/10.1021/jp710104d">10.1021/jp710104d</a>.</p> <p><a name="ozoneRef2"></a></p> <p>(2) Curtiss, L. A.; Redfern, P. C.; Raghavachari, K., "Gaussian-4 theory," <i>J. Chem. Phys.</i>, <b>2007</b>, <i>126</i>, 084108, DOI: <a href="http://dx.doi.org/10.1063/1.2436888">10.1063/1.2436888</a> </p> <p>(3) Curtiss, L. A.; Redfern, P. C.; Raghavachari, K., "Gaussian-4 theory using<br> reduced order perturbation theory," <i>J. Chem. Phys.</i>, <b>2007</b>, <i>127</i>, 124105-8, DOI: <a href="http://dx.doi.org/10.1063/1.2770701">10.1063/1.2770701</a>.</p> <h3>InChIs</h3> <p><b>Reaction 1 product</b>: <span class="chem:inchi">InChI=1/C2H2O3/c1-2-4-5-3-1/h1-2H</span></p> <p><b>Reaction 2 product</b>: <span class="chem:inchi">InChI=1/C2H4O3/c1-2-4-5-3-1/h1-2H2</span></p>  </div> <p class="bottom"> <span class="cat"><a href="/blog/archives/category/qm-method/g3" rel="category tag">G3</a> &<a href="/blog/archives/category/reactions/ozonolysis" rel="category tag">ozonolysis</a></span> <span class="user">Steven Bachrach</span> <span class="date">23 Apr 2008</span> <span class="comments">No Comments</span> </p> </div>   <p class="nocomments">Comments are closed.</p> <p align="center"></p> </div> <div id="sidebar"> <ul> <li class="box"> <h2> Categories </h2> <ul> <li class="cat-item cat-item-25"> <a href="/blog/archives/category/acidity">Acidity</a> (12) </li> <li class="cat-item cat-item-3"> <a 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</li> <li class="cat-item cat-item-38"> <a href="/blog/archives/category/reactions/pseudopericyclic">pseudopericyclic</a> (4) </li> <li class="cat-item cat-item-63"> <a href="/blog/archives/category/reactions/strecker">Strecker</a> (1) </li> <li class="cat-item cat-item-24"> <a href="/blog/archives/category/reactions/substitution">Substitution</a> (6) </li> <li class="cat-item cat-item-93"> <a href="/blog/archives/category/reactions/wittig">Wittig</a> (1) </li> </ul> </li> <li class="cat-item cat-item-87"> <a href="/blog/archives/category/second-edition">Second Edition</a> (3) </li> <li class="cat-item cat-item-11"> <a href="/blog/archives/category/solvation">Solvation</a> (17) </li> <li class="cat-item cat-item-77"> <a href="/blog/archives/category/stereochemistry">Stereochemistry</a> (2) </li> <li class="cat-item cat-item-68"> <a href="/blog/archives/category/stereoinduction">stereoinduction</a> (4) </li> <li class="cat-item cat-item-71"> <a href="/blog/archives/category/tunneling">Tunneling</a> (26) </li> <li class="cat-item cat-item-1"> <a href="/blog/archives/category/uncategorized">Uncategorized</a> (57) </li> <li class="cat-item cat-item-82"> <a href="/blog/archives/category/vibrational-frequencies">vibrational frequencies</a> (3) </li> </ul> </li> <li class="box"> <h2> Monthly </h2> <ul> <li><a href="/blog/archives/date/2019/06">June 2019</a></li> <li><a href="/blog/archives/date/2019/04">April 2019</a></li> <li><a href="/blog/archives/date/2019/03">March 2019</a></li> <li><a href="/blog/archives/date/2019/02">February 2019</a></li> <li><a href="/blog/archives/date/2019/01">January 2019</a></li> <li><a href="/blog/archives/date/2018/12">December 2018</a></li> <li><a href="/blog/archives/date/2018/11">November 2018</a></li> <li><a href="/blog/archives/date/2018/10">October 2018</a></li> <li><a href="/blog/archives/date/2018/09">September 2018</a></li> <li><a href="/blog/archives/date/2018/08">August 2018</a></li> <li><a href="/blog/archives/date/2018/07">July 2018</a></li> <li><a href="/blog/archives/date/2018/06">June 2018</a></li> <li><a href="/blog/archives/date/2018/05">May 2018</a></li> <li><a href="/blog/archives/date/2018/04">April 2018</a></li> <li><a href="/blog/archives/date/2018/03">March 2018</a></li> <li><a href="/blog/archives/date/2018/02">February 2018</a></li> <li><a href="/blog/archives/date/2018/01">January 2018</a></li> <li><a href="/blog/archives/date/2017/12">December 2017</a></li> <li><a href="/blog/archives/date/2017/11">November 2017</a></li> <li><a href="/blog/archives/date/2017/10">October 2017</a></li> <li><a href="/blog/archives/date/2017/09">September 2017</a></li> <li><a href="/blog/archives/date/2017/08">August 2017</a></li> <li><a href="/blog/archives/date/2017/07">July 2017</a></li> <li><a href="/blog/archives/date/2017/06">June 2017</a></li> <li><a href="/blog/archives/date/2017/05">May 2017</a></li> <li><a href="/blog/archives/date/2017/04">April 2017</a></li> <li><a href="/blog/archives/date/2017/03">March 2017</a></li> <li><a href="/blog/archives/date/2017/02">February 2017</a></li> <li><a href="/blog/archives/date/2017/01">January 2017</a></li> <li><a href="/blog/archives/date/2016/12">December 2016</a></li> <li><a href="/blog/archives/date/2016/11">November 2016</a></li> <li><a href="/blog/archives/date/2016/10">October 2016</a></li> <li><a href="/blog/archives/date/2016/09">September 2016</a></li> <li><a href="/blog/archives/date/2016/08">August 2016</a></li> <li><a href="/blog/archives/date/2016/07">July 2016</a></li> <li><a href="/blog/archives/date/2016/06">June 2016</a></li> <li><a href="/blog/archives/date/2016/05">May 2016</a></li> <li><a href="/blog/archives/date/2016/04">April 2016</a></li> <li><a href="/blog/archives/date/2016/03">March 2016</a></li> <li><a href="/blog/archives/date/2016/02">February 2016</a></li> <li><a href="/blog/archives/date/2016/01">January 2016</a></li> <li><a href="/blog/archives/date/2015/12">December 2015</a></li> <li><a href="/blog/archives/date/2015/11">November 2015</a></li> <li><a href="/blog/archives/date/2015/10">October 2015</a></li> <li><a href="/blog/archives/date/2015/09">September 2015</a></li> <li><a href="/blog/archives/date/2015/08">August 2015</a></li> <li><a href="/blog/archives/date/2015/07">July 2015</a></li> <li><a href="/blog/archives/date/2015/06">June 2015</a></li> <li><a href="/blog/archives/date/2015/05">May 2015</a></li> <li><a href="/blog/archives/date/2015/04">April 2015</a></li> <li><a href="/blog/archives/date/2015/03">March 2015</a></li> <li><a href="/blog/archives/date/2015/02">February 2015</a></li> <li><a href="/blog/archives/date/2015/01">January 2015</a></li> <li><a href="/blog/archives/date/2014/12">December 2014</a></li> <li><a href="/blog/archives/date/2014/11">November 2014</a></li> <li><a href="/blog/archives/date/2014/10">October 2014</a></li> <li><a href="/blog/archives/date/2014/09">September 2014</a></li> <li><a href="/blog/archives/date/2014/08">August 2014</a></li> <li><a href="/blog/archives/date/2014/07">July 2014</a></li> <li><a href="/blog/archives/date/2014/06">June 2014</a></li> <li><a href="/blog/archives/date/2014/05">May 2014</a></li> <li><a href="/blog/archives/date/2014/04">April 2014</a></li> <li><a href="/blog/archives/date/2014/03">March 2014</a></li> <li><a href="/blog/archives/date/2014/02">February 2014</a></li> <li><a href="/blog/archives/date/2014/01">January 2014</a></li> <li><a href="/blog/archives/date/2013/12">December 2013</a></li> <li><a href="/blog/archives/date/2013/11">November 2013</a></li> <li><a href="/blog/archives/date/2013/10">October 2013</a></li> <li><a href="/blog/archives/date/2013/09">September 2013</a></li> <li><a href="/blog/archives/date/2013/08">August 2013</a></li> <li><a href="/blog/archives/date/2013/07">July 2013</a></li> <li><a href="/blog/archives/date/2013/06">June 2013</a></li> <li><a href="/blog/archives/date/2013/05">May 2013</a></li> <li><a href="/blog/archives/date/2013/04">April 2013</a></li> <li><a href="/blog/archives/date/2013/03">March 2013</a></li> <li><a href="/blog/archives/date/2013/02">February 2013</a></li> <li><a href="/blog/archives/date/2013/01">January 2013</a></li> <li><a href="/blog/archives/date/2012/12">December 2012</a></li> <li><a href="/blog/archives/date/2012/11">November 2012</a></li> <li><a href="/blog/archives/date/2012/10">October 2012</a></li> <li><a href="/blog/archives/date/2012/09">September 2012</a></li> <li><a href="/blog/archives/date/2012/08">August 2012</a></li> <li><a href="/blog/archives/date/2012/07">July 2012</a></li> <li><a href="/blog/archives/date/2012/06">June 2012</a></li> <li><a href="/blog/archives/date/2012/05">May 2012</a></li> <li><a href="/blog/archives/date/2012/04">April 2012</a></li> <li><a href="/blog/archives/date/2012/03">March 2012</a></li> <li><a href="/blog/archives/date/2012/02">February 2012</a></li> <li><a href="/blog/archives/date/2012/01">January 2012</a></li> <li><a href="/blog/archives/date/2011/12">December 2011</a></li> <li><a href="/blog/archives/date/2011/11">November 2011</a></li> <li><a href="/blog/archives/date/2011/10">October 2011</a></li> <li><a href="/blog/archives/date/2011/09">September 2011</a></li> <li><a href="/blog/archives/date/2011/08">August 2011</a></li> <li><a href="/blog/archives/date/2011/07">July 2011</a></li> <li><a href="/blog/archives/date/2011/06">June 2011</a></li> <li><a href="/blog/archives/date/2011/05">May 2011</a></li> <li><a href="/blog/archives/date/2011/04">April 2011</a></li> <li><a href="/blog/archives/date/2011/03">March 2011</a></li> <li><a href="/blog/archives/date/2011/02">February 2011</a></li> <li><a href="/blog/archives/date/2011/01">January 2011</a></li> <li><a href="/blog/archives/date/2010/12">December 2010</a></li> <li><a href="/blog/archives/date/2010/11">November 2010</a></li> <li><a href="/blog/archives/date/2010/10">October 2010</a></li> <li><a href="/blog/archives/date/2010/09">September 2010</a></li> <li><a href="/blog/archives/date/2010/08">August 2010</a></li> <li><a href="/blog/archives/date/2010/07">July 2010</a></li> <li><a href="/blog/archives/date/2010/06">June 2010</a></li> <li><a href="/blog/archives/date/2010/05">May 2010</a></li> <li><a href="/blog/archives/date/2010/04">April 2010</a></li> <li><a href="/blog/archives/date/2010/03">March 2010</a></li> <li><a href="/blog/archives/date/2010/02">February 2010</a></li> <li><a href="/blog/archives/date/2010/01">January 2010</a></li> <li><a href="/blog/archives/date/2009/12">December 2009</a></li> <li><a href="/blog/archives/date/2009/11">November 2009</a></li> <li><a href="/blog/archives/date/2009/10">October 2009</a></li> <li><a href="/blog/archives/date/2009/09">September 2009</a></li> <li><a href="/blog/archives/date/2009/08">August 2009</a></li> <li><a href="/blog/archives/date/2009/07">July 2009</a></li> <li><a href="/blog/archives/date/2009/06">June 2009</a></li> <li><a href="/blog/archives/date/2009/05">May 2009</a></li> <li><a href="/blog/archives/date/2009/04">April 2009</a></li> <li><a href="/blog/archives/date/2009/03">March 2009</a></li> <li><a href="/blog/archives/date/2009/02">February 2009</a></li> <li><a href="/blog/archives/date/2009/01">January 2009</a></li> <li><a href="/blog/archives/date/2008/12">December 2008</a></li> <li><a href="/blog/archives/date/2008/11">November 2008</a></li> <li><a href="/blog/archives/date/2008/10">October 2008</a></li> <li><a href="/blog/archives/date/2008/09">September 2008</a></li> <li><a href="/blog/archives/date/2008/08">August 2008</a></li> <li><a href="/blog/archives/date/2008/07">July 2008</a></li> <li><a href="/blog/archives/date/2008/06">June 2008</a></li> <li><a href="/blog/archives/date/2008/05">May 2008</a></li> <li><a href="/blog/archives/date/2008/04">April 2008</a></li> <li><a href="/blog/archives/date/2008/03">March 2008</a></li> <li><a href="/blog/archives/date/2008/02">February 2008</a></li> <li><a href="/blog/archives/date/2008/01">January 2008</a></li> <li><a href="/blog/archives/date/2007/12">December 2007</a></li> <li><a href="/blog/archives/date/2007/11">November 2007</a></li> <li><a href="/blog/archives/date/2007/10">October 2007</a></li> <li><a href="/blog/archives/date/2007/09">September 2007</a></li> <li><a href="/blog/archives/date/2007/08">August 2007</a></li> <li><a href="/blog/archives/date/2007/07">July 2007</a></li> </ul> </li> </ul> <a rel="license" href="https://creativecommons.org/licenses/by-nd/3.0/"> <img alt="Creative Commons License" style="border-width:0" src="https://i.creativecommons.org/l/by-nd/3.0/88x31.png"> </a> <br>This work is licensed under a <a rel="license" href="https://creativecommons.org/licenses/by-nd/3.0/">Creative Commons Attribution-No Derivative Works 3.0 Unported License</a>. </div>  <div class="clear"></div> 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