{"id":17349,"date":"2017-01-20T19:44:03","date_gmt":"2017-01-20T19:44:03","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=17349"},"modified":"2017-03-10T11:08:56","modified_gmt":"2017-03-10T11:08:56","slug":"forming-a-stabilized-m-benzyne","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17349","title":{"rendered":"Forming a stabilized m-benzyne."},"content":{"rendered":"
\n

The story so far. Inspired by the report of the most polar neutral compound yet made<\/a>, I suggested some candidates based on the azulene ring system that if made might be even more polar. This then led to considering<\/a> a smaller \u03c0-analogue of azulene, m-benzyne. Here I ponder how a derivative of this molecule might be made, using computational profiling as one reality check.<\/p>\n

One reaction as envisaged is to prepare the penta-substituted benzene as shown below.<\/p>\n

\"\"<\/a><\/p>\n

Abstraction of the proton using strong base might result in 1,3-elimination of the leaving group X to form the m-benzyne. For the substituent X=Cl, a\u00a0\u03c9B97XD\/Def2-TZVPP\/SCRF=thf calculation (DOI: 10.14469\/hpc\/2057<\/a>) of the reaction profile shows a relatively large barrier to elimination, with an endothermic product.<\/p>\n

\"\"\"\"<\/a><\/p>\n

A better leaving group might be X=OTf. Unlike, X=Cl, this reaction is nicely exoenergic (\u0394\u0394G -10.6 kcal\/mol) with an\u00a0accessible\u00a0activation free energy of 22.5 kcal\/mol\u00a0(DOI: 10.14469\/hpc\/2066<\/a>, 10.14469\/hpc\/2123<\/a>, 10.14469\/hpc\/2096<\/a>)<\/p>\n

\"\"<\/p>\n

Perhaps then this, the smaller homologue of azulene, might indeed be capable of synthesis?<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

The story so far. Inspired by the report of the most polar neutral compound yet made, I suggested some candidates based on the azulene ring system that if made might be even more polar. This then led to considering a smaller \u03c0-analogue of azulene, m-benzyne. Here I ponder how a derivative of this molecule might […]<\/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":true,"_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":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[4,1086],"tags":[2043,1955,2042,2044],"ppma_author":[2661],"class_list":["post-17349","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","category-reaction-mechanism-2","tag-accessible-activation-free-energy","tag-aryne","tag-azulenes","tag-endothermic-product"],"yoast_head":"\nForming a stabilized m-benzyne. - 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=17349\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Forming a stabilized m-benzyne. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"The story so far. Inspired by the report of the most polar neutral compound yet made, I suggested some candidates based on the azulene ring system that if made might be even more polar. This then led to considering a smaller \u03c0-analogue of azulene, m-benzyne. Here I ponder how a derivative of this molecule might […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17349\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2017-01-20T19:44:03+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2017-03-10T11:08:56+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/01\/polar.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\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":"Forming a stabilized m-benzyne. - 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=17349","og_locale":"en_GB","og_type":"article","og_title":"Forming a stabilized m-benzyne. - Henry Rzepa's Blog","og_description":"The story so far. Inspired by the report of the most polar neutral compound yet made, I suggested some candidates based on the azulene ring system that if made might be even more polar. This then led to considering a smaller \u03c0-analogue of azulene, m-benzyne. Here I ponder how a derivative of this molecule might […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17349","og_site_name":"Henry Rzepa's Blog","article_published_time":"2017-01-20T19:44:03+00:00","article_modified_time":"2017-03-10T11:08:56+00:00","og_image":[{"url":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/01\/polar.svg","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=17349#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17349"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"Forming a stabilized m-benzyne.","datePublished":"2017-01-20T19:44:03+00:00","dateModified":"2017-03-10T11:08:56+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17349"},"wordCount":178,"commentCount":2,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17349#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2017\/01\/polar.svg","keywords":["accessible activation free energy","Aryne","Azulenes","endothermic product"],"articleSection":["Interesting chemistry","reaction mechanism"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17349#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17349","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17349","name":"Forming a stabilized m-benzyne. - 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Here I apply the principle to the polar azulene 4 explored in an earlier post, taking m-benzyne as a lower homologue of azulene as my starting point. m-Benzyne is a less\u00a0stable\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":3003,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=3003","url_meta":{"origin":17349,"position":1},"title":"Janus mechanisms (the past and the future): Reactions of the diazonium cation.","author":"Henry Rzepa","date":"December 11, 2010","format":false,"excerpt":"Janus was the mythological Roman god depicted as having two heads facing opposite directions, looking simultaneously into the past and the future. Some of the most ancient (i.e. 19th century) known reactions can be considered part of a chemical mythology; perhaps it is time for\u00a0a Janus-like look into their future.\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":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/12\/diazonium.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":17205,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=17205","url_meta":{"origin":17349,"position":2},"title":"Molecules of the year? The most polar neutral compound synthesized…","author":"Henry Rzepa","date":"December 18, 2016","format":false,"excerpt":"This, the fourth candidate provided by C&EN for a vote for the molecule of the year\u00a0as discussed here,\u00a0lays claim to the World's most polar neutral molecule (system 1 shown below). Here I explore\u00a0a strategy for extending that record. The claim for 1 (3 in\u00a0) is on the basis of its\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":12810,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=12810","url_meta":{"origin":17349,"position":3},"title":"Using a polar bond to flip: a follow up project.","author":"Henry Rzepa","date":"August 6, 2014","format":false,"excerpt":"In my earlier post on the topic, I discussed how inverting the polarity of the C-X bond from X=O to X=Be could flip the stereochemical course of the electrocyclic pericyclic reaction of a divinyl system. An obvious question would be: what happens at the half way stage, ie X=CH2? Well,\u2026","rel":"","context":"In "pericyclic"","block_context":{"text":"pericyclic","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=559"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":7344,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=7344","url_meta":{"origin":17349,"position":4},"title":"The first curly arrows. The d\u00e9nouement.","author":"Henry Rzepa","date":"July 23, 2012","format":false,"excerpt":"Recollect, Robinson was trying to explain why the nitroso group appears to be an o\/p director of aromatic electrophilic substitution. Using \u03c3\/\u03c0 orthogonality, I suggested that the (first ever) curly arrows as he drew them could not be the complete story, and that a transition state analysis would be needed.\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":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/07\/p-wheland.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":13047,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=13047","url_meta":{"origin":17349,"position":5},"title":"A computed mechanistic pathway for the formation of an amide from an acid and an amine in non-polar solution.","author":"Henry Rzepa","date":"November 12, 2014","format":false,"excerpt":"In London, one has the pleasures of attending occasional one day meetings at the Burlington House, home of the Royal Society of Chemistry. On November 5th this year, there was an excellent\u00a0meeting on the topic of Challenges in Catalysis,\u00a0and you can see the speakers and (some of) their slides here.\u2026","rel":"","context":"In "reaction mechanism"","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":[]}],"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\/17349","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=17349"}],"version-history":[{"count":14,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/17349\/revisions"}],"predecessor-version":[{"id":17375,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/17349\/revisions\/17375"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=17349"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=17349"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=17349"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=17349"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}