{"id":4375,"date":"2011-06-12T09:03:38","date_gmt":"2011-06-12T09:03:38","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=4375"},"modified":"2011-11-28T13:16:51","modified_gmt":"2011-11-28T13:16:51","slug":"more-is-more-the-dyotropic-rearrangement-of-12-dibromoethane","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4375","title":{"rendered":"More is more: the dyotropic rearrangement of 1,2-dibromoethane."},"content":{"rendered":"
\n

In the previous post<\/a>, \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.<\/p>\n

\"\"<\/a>

Dyotropic rearrangement of 1,2-dibromoethane.<\/p><\/div>\n

Subjected to B3LYP\/6-311G(d,p)<\/a> (with or without solvent field) yields a transition state with only one negative force constant. No tendency to distort from D2h<\/sub> symmetry then. Notice also how the migrating hydrogens did all the moving for ethane, but with a much heavier bromine replacing them, it is now the relatively light carbons and the hydrogens attached to them that instead carry the reaction.<\/p>\n

\"\"

Transition state for dyotropic rearrangement. Click for 3D.<\/p><\/div>What is more? Well, each Br has more valence electrons than H (7 vs 1), but of course the\u00a0C-Br bond is also more ionic. Time for\u00a0ELF to try to tell us what the electrons are up to.<\/p>\n

\"\"<\/a>

ELF analysis for the dyotropic rearrangement of 1,2-dibromoethane.<\/p><\/div>\n

This shows that the C-C region has 2.4 electrons; its actually gained some! The bromines each have 7.9 electrons in the valence shell in the form of two lone pair monosynaptic basins (and 27.5 in the core), and the remaining hydrogens on the carbon have ~2.15 each (0.15 having been ~extracted from the core of the bromine). The system has distorted from a pericyclic<\/strong> transfer of electrons to an ionic mechanism<\/strong>; an ion-triple to be precise. This is also not anti-aromatic. So here we see yet another way in which a forbidden (anti-aromatic) pericyclic reaction can distort. There are other ways still<\/a>!<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

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 B3LYP\/6-311G(d,p) (with or without solvent […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_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},"jetpack_post_was_ever_published":false},"categories":[],"tags":[563,560,564,2650,373],"ppma_author":[2661],"class_list":["post-4375","post","type-post","status-publish","format-standard","hentry","tag-dibromoethane","tag-dyotropic","tag-iontriple","tag-pericyclic","tag-tutorial-material"],"yoast_head":"\nMore is more: the dyotropic rearrangement of 1,2-dibromoethane. - 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=4375\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"More is more: the dyotropic rearrangement of 1,2-dibromoethane. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"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 B3LYP\/6-311G(d,p) (with or without solvent […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4375\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2011-06-12T09:03:38+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2011-11-28T13:16:51+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyobr.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":"More is more: the dyotropic rearrangement of 1,2-dibromoethane. - 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=4375","og_locale":"en_GB","og_type":"article","og_title":"More is more: the dyotropic rearrangement of 1,2-dibromoethane. - Henry Rzepa's Blog","og_description":"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 B3LYP\/6-311G(d,p) (with or without solvent […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4375","og_site_name":"Henry Rzepa's Blog","article_published_time":"2011-06-12T09:03:38+00:00","article_modified_time":"2011-11-28T13:16:51+00:00","og_image":[{"url":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyobr.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=4375#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4375"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"More is more: the dyotropic rearrangement of 1,2-dibromoethane.","datePublished":"2011-06-12T09:03:38+00:00","dateModified":"2011-11-28T13:16:51+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4375"},"wordCount":304,"commentCount":3,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4375#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyobr.jpg","keywords":["dibromoethane","dyotropic","iontriple","pericyclic","Tutorial material"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4375#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4375","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4375","name":"More is more: the dyotropic rearrangement of 1,2-dibromoethane. - 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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\u2026","rel":"","context":"In \"dyotropic\"","block_context":{"text":"dyotropic","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=dyotropic"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/06\/dyob.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":4340,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=4340","url_meta":{"origin":4375,"position":1},"title":"Less is more: the dyotropic rearrangement of ethane","author":"Henry Rzepa","date":"June 11, 2011","format":false,"excerpt":"In a time when large (molecules) are considered beautiful (or the corollary that beauty must be big), it is good to reflect that small molecules may teach us something as well. 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":10706,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=10706","url_meta":{"origin":4375,"position":2},"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":18856,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18856","url_meta":{"origin":4375,"position":3},"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. 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He had constructed a model of the reaction he wanted to undertake, perhaps with\u2026","rel":"","context":"In "Historical"","block_context":{"text":"Historical","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=565"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2021\/01\/sden.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]}],"jetpack_likes_enabled":false,"authors":[{"term_id":2661,"user_id":1,"is_guest":0,"slug":"admin","display_name":"Henry Rzepa","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","0":null,"1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":""}],"_links":{"self":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4375","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4375"}],"version-history":[{"count":1,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4375\/revisions"}],"predecessor-version":[{"id":5682,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/4375\/revisions\/5682"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4375"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4375"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4375"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=4375"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}