{"id":4413,"date":"2011-06-12T15:12:07","date_gmt":"2011-06-12T15:12:07","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=4413"},"modified":"2011-06-12T15:12:07","modified_gmt":"2011-06-12T15:12:07","slug":"buses-and-dyotropic-rearrangements-always-come-in-threes","status":"publish","type":"post","link":"https:\/\/rzepa.net\/blog\/2011\/06\/12\/buses-and-dyotropic-rearrangements-always-come-in-threes\/","title":{"rendered":"Buses (and dyotropic rearrangements) always come in threes."},"content":{"rendered":"<p>The last two posts have played a game of find the electrons. We saw how the dyotropic rearrangement of <a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=4340\" target=\"_blank\">ethane<\/a> borrowed electrons from the C-C bond, and how\u00a0<a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=4375\" target=\"_blank\">1,2,dibromoethane<\/a> went ionic on us. How about this mixed system, in which a hydrogen and a BH<sub>2<\/sub> swap their positions?<\/p>\n<figure id=\"attachment_4414\" aria-describedby=\"caption-attachment-4414\" style=\"width: 258px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyob.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-4414\" title=\"dyob\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyob.jpg\" alt=\"\" width=\"258\" height=\"108\" \/><\/a><figcaption id=\"caption-attachment-4414\" class=\"wp-caption-text\">Dyotropic rearrangement involving boron and hydrogen.<\/figcaption><\/figure>\n<p>It is yet again different. Unlike the ethane system, this C<sub>2v<\/sub>-symmetric system is a true transition state, with no other distorsions. The C-C distance is an unusual 1.729\u00c5, whilst the C-B distances are a more normal 1.61\u00c5.<\/p>\n<table border=\"0\">\n<tbody>\n<tr>\n<td><figure id=\"attachment_4416\" aria-describedby=\"caption-attachment-4416\" style=\"width: 200px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-4416\" title=\"dyob-ts\" onclick=\"jmolInitialize('..\/Jmol\/');jmolSetAppletColor('yellow');jmolApplet([450,450],'load wp-content\/uploads\/2011\/06\/dyob.log; frame 23;connect (atomno=7) (atomno=6) NONE; zoom 100;vectors on;vectors 4;vectors scale 5.0; color vectors green; vibration 20;animation mode loop;measure 6 7;');\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyob-ts.jpg\" alt=\"\" width=\"200\" height=\"171\" \/><figcaption id=\"caption-attachment-4416\" class=\"wp-caption-text\">Transition state for H\/BH2 transposition. Click for 3D.<\/figcaption><\/figure><\/td>\n<td>\n<p><figure id=\"attachment_4422\" aria-describedby=\"caption-attachment-4422\" style=\"width: 200px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/hdl.handle.net\/10042\/to-8590\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-4422\" title=\"dyob-irc\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyob-irc.jpg\" alt=\"\" width=\"200\" height=\"184\" \/><\/a><figcaption id=\"caption-attachment-4422\" class=\"wp-caption-text\">Intrinsic reaction coordinate for the dyotropic rearrangement.<\/figcaption><\/figure><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>The ELF partitioning shows 1.81 electrons in C-B disynaptic basins (red, below), and 1.91 electrons in a trisynaptic\u00a0C-H-C basin (yellow, below), or 5.53 in total. No discrete C-C basin is found, and no evidence either of ionicity as with dibromoethane.<\/p>\n<figure id=\"attachment_4417\" aria-describedby=\"caption-attachment-4417\" style=\"width: 233px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyob-elf.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-4417\" title=\"dyob-elf\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyob-elf.jpg\" alt=\"\" width=\"233\" height=\"258\" \/><\/a><figcaption id=\"caption-attachment-4417\" class=\"wp-caption-text\">ELF analysis.<\/figcaption><\/figure>\n<p>Finally, adding two electrons into the system, as with NH<sub>2<\/sub> replacing BH<sub>2<\/sub>, produces a similar result but now with the\u00a0C&#8230;C region populated with 2.22 electrons (the surprise is that this extra electron pair is NOT associated with the nitrogen). These extra electrons reduces the\u00a0C-C bond length to 1.395\u00c5.<\/p>\n<figure id=\"attachment_4428\" aria-describedby=\"caption-attachment-4428\" style=\"width: 232px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/hdl.handle.net\/10042\/to-8591\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-4428\" title=\"dyon-elf\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyon-elf.jpg\" alt=\"\" width=\"232\" height=\"307\" \/><\/a><figcaption id=\"caption-attachment-4428\" class=\"wp-caption-text\">ELF analysis for NH2\/H transposition.<\/figcaption><\/figure>\n<p>What an adventure. It reminds us never to take for granted where the electrons are in a molecule (or the transition states for its reactions), although to be fair we can normally guess pretty well.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The last two posts have played a game of find the electrons. We saw how the dyotropic rearrangement of ethane borrowed electrons from the C-C bond, and how\u00a01,2,dibromoethane went ionic on us. How about this mixed system, in which a hydrogen and a BH2 swap their positions? It is yet again different. Unlike the ethane [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[847,1884,2489],"class_list":["post-4413","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-dyotropic","tag-pericyclic","tag-tutorial-material"],"_links":{"self":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/posts\/4413","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/comments?post=4413"}],"version-history":[{"count":0,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/posts\/4413\/revisions"}],"wp:attachment":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/media?parent=4413"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/categories?post=4413"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/tags?post=4413"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}