{"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":"2017-01-20T19:44:03","modified_gmt":"2017-01-20T19:44:03","slug":"forming-a-stabilized-m-benzyne","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/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,"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":[6,1085],"tags":[2002,1965,2007,2027],"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"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-4vP","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/17349","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=17349"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/17349\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=17349"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=17349"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=17349"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}