{"id":5950,"date":"2011-12-15T17:36:19","date_gmt":"2011-12-15T17:36:19","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=5950"},"modified":"2013-05-07T17:29:43","modified_gmt":"2013-05-07T16:29:43","slug":"molecular-gymnastics-in-22-cycloadditions-two-different-moves-compared","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950","title":{"rendered":"Molecular gymnastics in  2+2 cycloadditions. Two different moves compared."},"content":{"rendered":"<div class=\"kcite-section\" kcite-section-id=\"5950\">\n<p>The <a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=5927\" target=\"_blank\">previous post<\/a> showed how the 2+2 cycloaddition of an alkene could occur by a sort of sideways insinuation of the bonds. I have also shown how the same reaction can occur with a dramatic rotation of one of the double bonds. This post compares the two moves side by side.<\/p>\n<p style=\"text-align: center;\"><a href=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/a+s.svg\"><img decoding=\"async\" class=\"aligncenter  wp-image-5952\" title=\"a+s\" alt=\"\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/a+s.svg\" width=\"300\" \/><\/a><\/p>\n<table style=\"margin-left: auto; margin-right: auto;\" border=\"1\">\n<tbody>\n<tr>\n<td align=\"centre\"><a href=\"http:\/\/hdl.handle.net\/10042\/to-11413\" target=\"_blank\">0.0<\/a><\/td>\n<td align=\"centre\"><a href=\"http:\/\/hdl.handle.net\/10042\/to-11415\" target=\"_blank\">5.3 kcal\/mol<\/a><\/td>\n<\/tr>\n<tr>\n<td>\n<div id=\"attachment_5933\" style=\"width: 232px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/hdl.handle.net\/10042\/to-11331\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-5933\" class=\" wp-image-5933  \" title=\"14d1\" alt=\"\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/14d1.gif\" width=\"222\" height=\"136\" \/><\/a><p id=\"caption-attachment-5933\" class=\"wp-caption-text\">The forbidden dance<\/p><\/div>\n<\/td>\n<td>\n<div id=\"attachment_5958\" style=\"width: 213px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/hdl.handle.net\/10042\/to-11399\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-5958\" class=\" wp-image-5958 \" title=\"2a+2s-CS\" alt=\"\" src=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/2a+2s-CS1.gif\" width=\"203\" height=\"143\" \/><\/a><p id=\"caption-attachment-5958\" class=\"wp-caption-text\">The allowed dance.<\/p><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>As is sometimes the case in real life, the forbidden option has the lower activation barrier!<\/p>\n<!-- kcite active, but no citations found -->\n<\/div> <!-- kcite-section 5950 -->","protected":false},"excerpt":{"rendered":"<p>The previous post showed how the 2+2 cycloaddition of an alkene could occur by a sort of sideways insinuation of the bonds. I have also shown how the same reaction can occur with a dramatic rotation of one of the double bonds. This post compares the two moves side by side. 0.0 5.3 kcal\/mol As [&hellip;]<\/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_feature_clip_id":0,"_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":[4],"tags":[2650,373],"ppma_author":[2661],"class_list":["post-5950","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-pericyclic","tag-tutorial-material"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.8 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Molecular gymnastics in 2+2 cycloadditions. Two different moves compared. - Henry Rzepa&#039;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=5950\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Molecular gymnastics in 2+2 cycloadditions. Two different moves compared. - Henry Rzepa&#039;s Blog\" \/>\n<meta property=\"og:description\" content=\"The previous post showed how the 2+2 cycloaddition of an alkene could occur by a sort of sideways insinuation of the bonds. I have also shown how the same reaction can occur with a dramatic rotation of one of the double bonds. This post compares the two moves side by side. 0.0 5.3 kcal\/mol As [&hellip;]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa&#039;s Blog\" \/>\n<meta property=\"article:published_time\" content=\"2011-12-15T17:36:19+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2013-05-07T16:29:43+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/a+s.svg\" \/>\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<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Molecular gymnastics in 2+2 cycloadditions. Two different moves compared. - Henry Rzepa&#039;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=5950","og_locale":"en_GB","og_type":"article","og_title":"Molecular gymnastics in 2+2 cycloadditions. Two different moves compared. - Henry Rzepa&#039;s Blog","og_description":"The previous post showed how the 2+2 cycloaddition of an alkene could occur by a sort of sideways insinuation of the bonds. I have also shown how the same reaction can occur with a dramatic rotation of one of the double bonds. This post compares the two moves side by side. 0.0 5.3 kcal\/mol As [&hellip;]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950","og_site_name":"Henry Rzepa&#039;s Blog","article_published_time":"2011-12-15T17:36:19+00:00","article_modified_time":"2013-05-07T16:29:43+00:00","og_image":[{"url":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/a+s.svg","type":"","width":"","height":""}],"author":"Henry Rzepa","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Henry Rzepa"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"Molecular gymnastics in 2+2 cycloadditions. Two different moves compared.","datePublished":"2011-12-15T17:36:19+00:00","dateModified":"2013-05-07T16:29:43+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950"},"wordCount":96,"commentCount":0,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/a+s.svg","keywords":["pericyclic","Tutorial material"],"articleSection":["Interesting chemistry"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950","name":"Molecular gymnastics in 2+2 cycloadditions. Two different moves compared. - Henry Rzepa&#039;s Blog","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950#primaryimage"},"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/a+s.svg","datePublished":"2011-12-15T17:36:19+00:00","dateModified":"2013-05-07T16:29:43+00:00","author":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"breadcrumb":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950#breadcrumb"},"inLanguage":"en-GB","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950"]}]},{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950#primaryimage","url":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/a+s.svg","contentUrl":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/12\/a+s.svg"},{"@type":"BreadcrumbList","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5950#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog"},{"@type":"ListItem","position":2,"name":"Molecular gymnastics in 2+2 cycloadditions. Two different moves compared."}]},{"@type":"WebSite","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#website","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/","name":"Henry Rzepa&#039;s Blog","description":"Chemistry with a twist","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-GB"},{"@type":"Person","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281","name":"Henry Rzepa","image":{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g370be3a7397865e4fd161aefeb0a5a85","url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","caption":"Henry Rzepa"},"description":"Henry Rzepa is Emeritus Professor of Computational Chemistry at Imperial College London.","sameAs":["https:\/\/orcid.org\/0000-0002-8635-8390"],"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?author=1"}]}},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/pDef7-1xY","jetpack-related-posts":[{"id":26962,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=26962","url_meta":{"origin":5950,"position":0},"title":"Detecting anomeric effects in tetrahedral boron bearing four oxygen substituents.","author":"Henry Rzepa","date":"April 30, 2024","format":false,"excerpt":"In an earlier post, I discussed a phenomenon known as the \"anomeric effect\" exhibited by tetrahedral carbon compounds with four C-O bonds. Each oxygen itself bears two bonds and has two lone pairs, and either of these can align with one of three other C-O bonds to generate an anomeric\u2026","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/04\/Screenshot-304.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/04\/Screenshot-304.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/04\/Screenshot-304.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/04\/Screenshot-304.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":13033,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13033","url_meta":{"origin":5950,"position":1},"title":"The solvation of ion pairs.","author":"Henry Rzepa","date":"November 6, 2014","format":false,"excerpt":"Solvolytic mechanisms are amongst the oldest studied, but reproducing their characteristics using computational methods has been a challenging business. This post was inspired by reading Steve Bachrach's post, itself alluding to this aspect in the title \"Computationally handling ion pairs\". It references this recent article on the topic in which\u2026","rel":"","context":"In &quot;reaction mechanism&quot;","block_context":{"text":"reaction mechanism","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1086"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":18652,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18652","url_meta":{"origin":5950,"position":2},"title":"Chemical Bonds at the 21st Century &#8211; 2017:  the Bond Slam.","author":"Henry Rzepa","date":"August 2, 2017","format":false,"excerpt":"It is always interesting to observe conference experiments taking place. The traditional model involves travelling to a remote venue, staying in a hotel, selecting sessions to attend from a palette of parallel streams and then interweaving chatting to colleagues both old and new over coffee, lunch, dinner or excursions. Sometimes\u2026","rel":"","context":"In &quot;Bond slam&quot;","block_context":{"text":"Bond slam","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2237"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/08\/BH3F.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":878,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=878","url_meta":{"origin":5950,"position":3},"title":"It&#8217;s Hexa-coordinate carbon Spock &#8211; but not as we know it!","author":"Henry Rzepa","date":"October 2, 2009","format":false,"excerpt":"Science is about making connections. And these can often be made between the most unlikely concepts. Thus in the posts I have made about pentavalent carbon, one can identify a series of conceptual connections. The\u00a0first, by Matthias\u00a0Bickelhaupt and co, resulted in the suggestion of a possible frozen\u00a0SN2 transition state. They\u2026","rel":"","context":"In &quot;Hypervalency&quot;","block_context":{"text":"Hypervalency","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=7"},"img":{"alt_text":"The HOMO orbital","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2009\/09\/C5-homo1.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":8085,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8085","url_meta":{"origin":5950,"position":4},"title":"Secrets of a university tutor. An exercise in mechanistic logic: first d\u00e9nouement.","author":"Henry Rzepa","date":"October 28, 2012","format":false,"excerpt":"The reaction described in the previous post (below) is an unusual example of nucleophilic attack at an sp2-carbon centre, reportedly resulting in inversion of configuration. One can break it down to a sequence of up to eight individual steps, which makes teaching it far easier. But how real is that\u2026","rel":"","context":"In &quot;Interesting chemistry&quot;","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/10\/triflate.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":6102,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=6102","url_meta":{"origin":5950,"position":5},"title":"Secrets of a university tutor: dissection of a reaction mechanism.","author":"Henry Rzepa","date":"January 25, 2012","format":false,"excerpt":"Its a bit like a jigsaw puzzle in reverse, finding out to disassemble a chemical reaction into the pieces it is made from, and learning the rules that such reaction jigsaws follow. The following takes about 45-50 minutes to follow through with a group of students. The problem is initially\u2026","rel":"","context":"In \"chemical reaction\"","block_context":{"text":"chemical reaction","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=chemical-reaction"},"img":{"alt_text":"","src":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/01\/pericyclic-tutorial.svg","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","author_category":"1","first_name":"Henry","last_name":"Rzepa","user_url":"https:\/\/orcid.org\/0000-0002-8635-8390","job_title":"","description":"Henry Rzepa is Emeritus Professor of Computational Chemistry at Imperial College London."}],"_links":{"self":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/5950","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=5950"}],"version-history":[{"count":13,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/5950\/revisions"}],"predecessor-version":[{"id":10380,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/5950\/revisions\/10380"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5950"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5950"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5950"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=5950"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}