{"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":"2011-11-28T13:16:25","modified_gmt":"2011-11-28T13:16:25","slug":"buses-and-dyotropic-rearrangements-always-come-in-threes","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413","title":{"rendered":"Buses (and dyotropic rearrangements) always come in threes."},"content":{"rendered":"
\n

The last two posts have played a game of find the electrons. We saw how the dyotropic rearrangement of ethane<\/a> borrowed electrons from the C-C bond, and how\u00a01,2,dibromoethane<\/a> went ionic on us. How about this mixed system, in which a hydrogen and a BH2<\/sub> swap their positions?<\/p>\n

\"\"<\/a>

Dyotropic rearrangement involving boron and hydrogen.<\/p><\/div>\n

It is yet again different. Unlike the ethane system, this C2v<\/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\n\n\n
\"\"

Transition state for H\/BH2 transposition. Click for 3D.<\/p><\/div><\/td>\n

\n

\"\"<\/a>

Intrinsic reaction coordinate for the dyotropic rearrangement.<\/p><\/div><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

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

\"\"<\/a>

ELF analysis.<\/p><\/div>\n

Finally, adding two electrons into the system, as with NH2<\/sub> replacing BH2<\/sub>, produces a similar result but now with the\u00a0C…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

\"\"<\/a>

ELF analysis for NH2\/H transposition.<\/p><\/div>\n

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\n<\/div> ","protected":false},"excerpt":{"rendered":"

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 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":5,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[],"tags":[560,2650,373],"ppma_author":[2661],"class_list":["post-4413","post","type-post","status-publish","format-standard","hentry","tag-dyotropic","tag-pericyclic","tag-tutorial-material"],"yoast_head":"\nBuses (and dyotropic rearrangements) always come in threes. - Henry Rzepa's Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Buses (and dyotropic rearrangements) always come in threes. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"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 […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2011-06-12T15:12:07+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2011-11-28T13:16:25+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyob.jpg\" \/>\n<meta name=\"author\" content=\"Henry Rzepa\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Henry Rzepa\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Buses (and dyotropic rearrangements) always come in threes. - Henry Rzepa's Blog","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413","og_locale":"en_GB","og_type":"article","og_title":"Buses (and dyotropic rearrangements) always come in threes. - Henry Rzepa's Blog","og_description":"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 […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413","og_site_name":"Henry Rzepa's Blog","article_published_time":"2011-06-12T15:12:07+00:00","article_modified_time":"2011-11-28T13:16:25+00:00","og_image":[{"url":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyob.jpg","type":"","width":"","height":""}],"author":"Henry Rzepa","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Henry Rzepa","Estimated reading time":"1 minute"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"Buses (and dyotropic rearrangements) always come in threes.","datePublished":"2011-06-12T15:12:07+00:00","dateModified":"2011-11-28T13:16:25+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413"},"wordCount":284,"commentCount":1,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyob.jpg","keywords":["dyotropic","pericyclic","Tutorial material"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4413","name":"Buses (and dyotropic rearrangements) always come in threes. - 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Take ethane. Is there anything left which has not been said about it already? Well, consider the reaction below,\u2026","rel":"","context":"In \"animation\"","block_context":{"text":"animation","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=animation"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/c2h6.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":4375,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4375","url_meta":{"origin":4413,"position":1},"title":"More is more: the dyotropic rearrangement of 1,2-dibromoethane.","author":"Henry Rzepa","date":"June 12, 2011","format":false,"excerpt":"In the previous post, \u00a0I discussed what we could learn from ethane by forcing it into a pericyclic dyotropic rearrangement. We saw how it voraciously scavenged two electrons from the \u00a0C-C bond to achieve this. What if we give it more electrons? Thus 1,2-dibromoethane undergoing the same reaction. Subjected to\u2026","rel":"","context":"In \"dibromoethane\"","block_context":{"text":"dibromoethane","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=dibromoethane"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyobr.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":18856,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18856","url_meta":{"origin":4413,"position":2},"title":"Dyotropic Ring Expansion: more mechanistic reality checks.","author":"Henry Rzepa","date":"October 1, 2017","format":false,"excerpt":"I noted in my WATOC conference report\u00a0a presentation describing the use of calculated reaction barriers (and derived rate constants) as mechanistic reality checks. Computations, it was claimed, have now reached a level of accuracy whereby a barrier calculated as being 6 kcal\/mol too high can start ringing mechanistic alarm bells.\u2026","rel":"","context":"In "pericyclic"","block_context":{"text":"pericyclic","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=559"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/09\/dyotropic.jpeg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":10706,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=10706","url_meta":{"origin":4413,"position":3},"title":"Mechanistic arrow pushing. A proposed addition to its rules.","author":"Henry Rzepa","date":"June 12, 2013","format":false,"excerpt":"A little while ago, I set out some interpretations of how to push curly arrows. I also appreciate that some theoretically oriented colleagues regard\u00a0the technique as neither useful nor in the least rigorous,\u00a0whereas towards the other extreme\u00a0many synthetically minded chemists view the ability to push a reasonable\u00a0set of arrows for\u2026","rel":"","context":"In "Curly arrows"","block_context":{"text":"Curly arrows","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2327"},"img":{"alt_text":"12-16","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/06\/12-16.gif?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":27944,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=27944","url_meta":{"origin":4413,"position":4},"title":"A one-electron bond in methyl-\u03bb1-borane.","author":"Henry Rzepa","date":"October 9, 2024","format":false,"excerpt":"In exploring one-electron carbon-carbon bonds, I had noted previously that both hexafluoroethane and ethane itself could each lose an electron to produce such species. A discussion developed in which a molecule isoelectronic with ethane radical cation, namely the methyl-\u03bb1-borane radical (H3B-CH3) was proposed by Jacob. The optimised structure at the\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":8961,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8961","url_meta":{"origin":4413,"position":5},"title":"The mechanism of the Benzidine rearrangement.","author":"Henry Rzepa","date":"January 6, 2013","format":false,"excerpt":"The benzidine rearrangement is claimed to be an example of the quite rare\u00a0[5,5] sigmatropic migration, which is a ten-electron homologation of the very common [3,3] sigmatropic reaction (e.g. the Cope or Claisen). Some benzidine rearrangements are indeed thought to go through the [3,3] route. The topic has been reviewed here.\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"NCI surface. 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