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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 » 2013 » February</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"> <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"> <h2 class="post-title">Archive for February, 2013</h2> <div class="box"> <h2><a href="/blog/archives/2629" rel="bookmark" title="Permanent Link: Musings about C<sub>2</sub>">Musings about C<sub>2</sub></a></h2> <div class="post-content"> <p>A short note here mainly to call to the reader’s attention a fascinating “trialogue” on the C<sub>2</sub> molecule.<a href="#trialogueR1"><sup>1</sup></a> Shaik, Danovich, Wu, Su, Rzepa, and Hiberty<a href="#trialogueR2"><sup>2</sup></a> recently presented a full CI study of C<sub>2</sub> and concluded that the molecule contains a quadruple bond (see my <a href="/blog/archives/2204">previous post on this paper</a>). This work was inspired in part by a <a href="http://www.ch.imperial.ac.uk/rzepa/blog/?p=3065">blog post</a> by Henry Rzepa.</p> <p>The trialogue<a href="#trialogueR1"><sup>1</sup></a> is a conversation between Sason Shaik, Henry Rzepa and Roald Hoffmann about the nature of C<sub>2</sub>, its 4<sup>th</sup> bond, its diradical character, and some historical detours to see how some of our theoretical chemistry ancestors came close to proposing a quadruple bond. The discussion weaves together simple MO pictures, simple VB models, and the need for much more sophisticated analysis to ultimately approach the truth. Very much worth pointing out is the careful analysis of trying to tease out bond dissociation energies, especially analyzing the assumptions made here – including the possibility of errors in the experiments and not just errors in the computations! This is a very enjoyable read, following these three theoreticians as they traipse about the complex C<sub>2</sub> landscape!</p> <h3>References</h3> <p><a name="trialogueR1"></a></p> <p>(1) Shaik, S.; Rzepa, H. S.; Hoffmann, R. "One Molecule, Two Atoms, Three Views, Four Bonds?," <i>Angew. Chem. Int. Ed.</i> <b>2013</b>, <i>52</i>, 3020-3033, DOI: <a href="http://dx.doi.org/10.1002/anie.201208206">10.1002/anie.201208206</a>.</p> <p><a name="trialogueR2"></a></p> <p>(2) Shaik, S.; Danovich, D.; Wu, W.; Su, P.; Rzepa, H. S.; Hiberty, P. C. "Quadruple bonding in C2 and analogous eight-valence electron species," <i>Nat. Chem.</i> <b>2012</b>, <i>4</i>, 195-200, DOI: <a href="http://dx.doi.org/10.1038/nchem.1263">10.1038/nchem.1263</a>.</p>  </div> <p class="bottom"> <span class="cat"><a href="/blog/archives/category/bond-dissociation-energy" rel="category tag">Bond Dissociation Energy</a></span> <span class="user">Steven Bachrach</span> <span class="date">28 Feb 2013</span> <span class="comments"><a href="/blog/archives/2629#comments">2 Comments</a></span> </p> </div> <div class="box"> <h2><a href="/blog/archives/2557" rel="bookmark" title="Permanent Link: Large water clusters and DFT performance">Large water clusters and DFT performance</a></h2> <div class="post-content"> <p>Truhlar has made a comparison of binding energies and relative energies of five (H<sub>2</sub>O)<sub>16</sub> clusters.<a href="#16waterRef1"><sup>1</sup></a> While technically not organic chemistry, this paper is of interest to the readership of this blog as it compares a very large collection of density functionals on a problem that involves extensive hydrogen bonding, a problem of interest to computational organic chemists.</p> <p>The CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ energies of clusters <b>1-5</b> (shown in Figure 1) were obtained by Yoo.<a href="#16waterRef2"><sup>2</sup></a> These clusters are notable not just for their size but also that they involve multiple water molecules involved in four hydrogen bonds. Truhlar has used these geometries to compute the energies using 73 different density functionals with the jun-cc-pVTZ basis set (see this <a href="/blog/archives/1943">post for a definition of the ‘jun’ basis sets</a>). Binding energies (relative to 16 isolated water molecules) were computed along with the 10 relative energies amongst the 5 different clusters. Combining the results of both types of energies, Truhlar finds that the best overall performance relative to CCSD(T) is obtained with ωB97X-D, a hybrid GGA method with a dispersion correction. The next two best performing functionals are LC-ωPBE-D3 and M05-2x. The best non-hybrid performance is with revPBE-D3 and B97-D.</p> <table align="center" border="0" cellspacing="0" cellpadding="4"> <tr align="center" valign="middle"> <td> <p></p> <div class="jmol" id="16water1"> <a onclick="return false"><br> <img src="/blog/wp-content/16water1.jpg" onclick="insertJmol('16water1',300,300,'16water1.xyz')"><br> </a> </div> <p><b>1</b> (0.0)</p> </td> <td> <p></p> <div class="jmol" id="16water2"> <a onclick="return false"><br> <img src="/blog/wp-content/16water2.jpg" onclick="insertJmol('16water2',300,300,'16water2.xyz')"><br> </a> </div> <p><b>2</b> (0.25)</p> </td> </tr> <tr align="center" valign="middle"> <td> <p></p> <div class="jmol" id="16water3"> <a onclick="return false"><br> <img src="/blog/wp-content/16water3.jpg" onclick="insertJmol('16water3',300,300,'16water3.xyz')"><br> </a> </div> <p><b>3</b> (0.42)</p> </td> <td> <p></p> <div class="jmol" id="16water4"> <a onclick="return false"><br> <img src="/blog/wp-content/16water4.jpg" onclick="insertJmol('16water4',300,300,'16water4.xyz')"><br> </a> </div> <p><b>4</b> (0.51)</p> </td> </tr> <tr align="center" valign="middle"> <td colspan="2"> <p></p> <div class="jmol" id="16water5"> <a onclick="return false"><br> <img src="/blog/wp-content/16water5.jpg" onclick="insertJmol('16water5',300,300,'16water5.xyz')"><br> </a> </div> <p><b>5</b> (0.54)</p> </td> </tr> </table> <p><b>Figure 1</b>. MP2/aug-cc-pVTZ optimized geometries and relative CCSD(T) energies (kcal mol<sup>-1</sup>) of (water)<sub>16</sub> clusters <b>1-5</b>. (<b>Don’t forget to click on any of these molecules above to launch <i>Jmol</i> to interactively view the 3-D structure.</b> This feature is true for all molecular structures displayed in all of my blog posts.)</p> <p>While this study can help guide selection of a functional, two words of caution. First, Truhlar notes that the best performing methods for the five (H<sub>2</sub>O)<sub>16</sub> clusters do not do a particularly great job in getting the binding and relative energies of water hexamers, suggesting that no single functional really stands out as best. Second, a better study would also involve geometry optimization using that particular functional. Since this was not done, one can garner little here about what method might be best for use in a typical study where a geometry optimization must also be carried out.</p> <h3>References</h3> <p><a name="16waterRef1"></a></p> <p>(1) Leverentz, H. R.; Qi, H. W.; Truhlar, D. G. "Assessing the Accuracy of Density<br> Functional and Semiempirical Wave Function Methods for Water Nanoparticles: Comparing Binding and Relative Energies of (H<sub>2</sub>O)<sub>16</sub> and (H<sub>2</sub>O)<sub>17</sub> to CCSD(T) Results," <i>J. Chem. Theor. Comput.</i> <b>2013</b>, ASAP, DOI: <a href="http://dx.doi.org/10.1021/ct300848z">10.1021/ct300848z</a>.</p> <p><a name="16waterRef2"></a></p> <p>(2) Yoo, S.; Aprà, E.; Zeng, X. C.; Xantheas, S. S. "High-Level Ab Initio Electronic Structure Calculations of Water Clusters (H<sub>2</sub>O)<sub>16</sub> and (H<sub>2</sub>O)<sub>17</sub>: A New Global Minimum for (H<sub>2</sub>O)<sub>16</sub>," <i>J. Phys. Chem. Lett.</i> <b>2010</b>, <i>1</i>, 3122-3127, DOI: <a href="http://dx.doi.org/10.1021/jz101245s">10.1021/jz101245s</a>.</p>  </div> <p class="bottom"> <span class="cat"><a href="/blog/archives/category/qm-method/dft" rel="category tag">DFT</a> &<a href="/blog/archives/category/hydrogen-bond" rel="category tag">Hydrogen bond</a> &<a href="/blog/archives/category/authors/truhlar" rel="category tag">Truhlar</a></span> <span class="user">Steven Bachrach</span> <span class="date">25 Feb 2013</span> <span class="comments"><a href="/blog/archives/2557#comments">1 Comment</a></span> </p> </div> <div class="box"> <h2><a href="/blog/archives/2545" rel="bookmark" title="Permanent Link: Bowls derived from C<sub>70</sub>">Bowls derived from C<sub>70</sub></a></h2> <div class="post-content"> <p>I have discussed a few bowl-shaped aromatics in this blog (see for example <a href="/blog/archives/2396">this</a> and <a href="/blog/archives/2246">this</a>). Kuo and Wu now report on a few bowls derived from C<sub>70</sub>-fullerenes.<a href="/blog/archives/date/2013/c70ref"><sup>1</sup></a> The bowl <b>1</b> was synthesized (along with a couple of other derivatives) and its x-ray structure obtained. As anticipated this polyclic aromatic is not planar, but rather a definite bowl, with a bowl depth of 2.28 Å. This is less curved than when the fragment is present in C<sub>70</sub>-fullerene.</p> <table align="center" border01 cellspacing="0" cellpadding="0"> <tr align="center"> <td> <p><img src="/blog/wp-content/C70bowlImage.png"><br><b>1</b></p> </td> </tr> </table> <p>Interestingly, this bowl does not invert through a planar transition state. The fully planar structure <b>1pl</b>, shown in Figure 1, is 116 kcal mol<sup>-1</sup> above the ground state bowl structure, computed at B3LYP/cc-pVDZ. Rather, the molecule inverts through a twisted S-shaped structure <b>1TS</b>, also shown in Figure 1. The activation barrier through <b>1TS</b> is 80 kcal mol<sup>-1</sup>. This suggests that <b>1</b> is static at room temperature, unlike corranulene which has an inversion barrier, through a <i>planar</i> transition state, of only 11 kcal mol<sup>-1</sup>. The much more concave structure of <b>1</b> than corranulene leads to the greatly increased strain in its all-planar TS. This implies that properly substituted analogues of <b>1</b> will be chiral and configurationally stable. Not remarked upon is that the inversion pathway, which will interchange enantiomers when <b>1</b> is properly substituted, follows a fully chiral path, as discussed in this <a href="/blog/archives/1849">post</a>.</p> <table align="center" border="0" cellspacing="0" cellpadding="4"> <tr align="center"> <td colspan="2"> <p></p> <div class="jmol" id="C70"> <a onclick="return false"><br> <img src="/blog/wp-content/C70bowl.jpg" onclick="insertJmol('C70',300,300,'C70bowl.xyz')"><br> </a> </div> <p><b>1</b></p> </td> </tr> <tr align="center" valign="middle"> <td> <p></p> <div class="jmol" id="C70TS"> <a onclick="return false"><br> <img src="/blog/wp-content/C70bowlTS.jpg" onclick="insertJmol('C70TS',300,300,'C70bowlTS.xyz')"><br> </a> </div> <p><b>1TS</b></p> </td> <td> <p></p> <div class="jmol" id="C70Planar"> <a onclick="return false"><br> <img src="/blog/wp-content/C70bowlPlanar.jpg" onclick="insertJmol('C70Planar',300,300,'C70bowlPlanar.xyz')"><br> </a> </div> <p><b>1pl</b></p> </td> </tr> </table> <p align="center"><b>Figure 1</b>. B3LYP/cc-pVDZ optimized geometries of <b>1</b>, <b>1TS</b>, and <b>1pl</b>.</p> <h3>Reference</h3> <p><a name="c70ref"></a></p> <p>(1) Wu, T.-C.; Chen, M.-K.; Lee, Y.-W.; Kuo, M.-Y.; Wu, Y.-T. "Bowl-Shaped Fragments of C<sub>70</sub> or Higher Fullerenes: Synthesis, Structural Analysis, and Inversion Dynamics," <i>Angew. Chem. Int. Ed.</i> <b>2013</b>, <i>52</i>, 1289-1293, DOI: <a href="http://dx.doi.org/10.1002/anie.201208200">10.1002/anie.201208200</a>.</p> <h3>InChIs</h3> <p><b>1</b>: InChI=1S/C38H14/c1-3-17-21-11-7-15-9-13-23-19-5-2-6-20-24-14-10-16-8-12-22-18(4-1)27(17)33-35-29(21)25(15)31(23)37(35)34(28(19)20)38-32(24)26(16)30(22)36(33)38/h1-14H<br> InChIKey=KLCLRPVBVWXTPN-UHFFFAOYSA-N</p>  </div> <p class="bottom"> <span class="cat"><a href="/blog/archives/category/aromaticity" rel="category tag">Aromaticity</a></span> <span class="user">Steven Bachrach</span> <span class="date">06 Feb 2013</span> <span class="comments"><a href="/blog/archives/2545#respond">No Comments</a></span> </p> </div> <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 href="/blog/archives/category/aromaticity">Aromaticity</a> (91) </li> <li 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class="cat-item cat-item-13"> <a href="/blog/archives/category/reactions/12-addition">1,2-addition</a> (1) </li> <li class="cat-item cat-item-35"> <a href="/blog/archives/category/reactions/aldol">aldol</a> (4) </li> <li class="cat-item cat-item-32"> <a href="/blog/archives/category/reactions/bergman-cyclization">Bergman cyclization</a> (6) </li> <li class="cat-item cat-item-44"> <a href="/blog/archives/category/reactions/claisen-rearrangement">Claisen rearrangement</a> (2) </li> <li class="cat-item cat-item-10"> <a href="/blog/archives/category/reactions/cope-rearrangement">Cope Rearrangement</a> (5) </li> <li class="cat-item cat-item-69"> <a href="/blog/archives/category/reactions/cycloadditions">cycloadditions</a> (12) </li> <li class="cat-item cat-item-23"> <a href="/blog/archives/category/reactions/diels-alder">Diels-Alder</a> (26) </li> <li class="cat-item cat-item-47"> <a href="/blog/archives/category/reactions/electrocyclization">electrocyclization</a> (11) </li> <li class="cat-item cat-item-76"> <a href="/blog/archives/category/reactions/electrophilic-aromatic-substitution">electrophilic aromatic substitution</a> (1) </li> <li class="cat-item cat-item-5"> <a href="/blog/archives/category/reactions/ene-reaction">ene reaction</a> (1) </li> <li class="cat-item cat-item-52"> <a href="/blog/archives/category/reactions/hajos-parrish-reaction">Hajos-Parrish Reaction</a> (1) </li> <li class="cat-item cat-item-61"> <a href="/blog/archives/category/reactions/mannich">Mannich</a> (2) </li> <li class="cat-item cat-item-64"> <a href="/blog/archives/category/reactions/michael-addition">Michael addition</a> (5) </li> <li class="cat-item cat-item-40"> <a href="/blog/archives/category/reactions/ozonolysis">ozonolysis</a> (1) </li> <li class="cat-item cat-item-43"> <a href="/blog/archives/category/reactions/proton-transfer">proton transfer</a> (1) </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" aria-current="page">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> 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