{"id":2828,"date":"2010-11-19T07:49:54","date_gmt":"2010-11-19T06:49:54","guid":{"rendered":"http:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=2828"},"modified":"2010-11-19T07:49:54","modified_gmt":"2010-11-19T06:49:54","slug":"can-a-cyclobutadiene-and-carbon-dioxide-co-exist-in-a-calixarene-cavity","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=2828","title":{"rendered":"Can a cyclobutadiene and carbon dioxide co-exist in a calixarene cavity?"},"content":{"rendered":"
\n

On 8th August this year, I posted<\/a> on a fascinating article that had just appeared in Science (DOI:\u00a010.1126\/science.1188002<\/a>), in which the crystal structure was reported of two small molecules,\u00a01,3-dimethyl cyclobutadiene\u00a0and\u00a0carbon dioxide, entrapped together inside a calixarene cavity. Other journals (e.g.\u00a0Nature Chemistry<\/em>, DOI:\u00a010.1038\/nchem.823<\/a>) ran the article as a research highlight <\/em>(where the purpose is not a critical analysis but more of an alerting service).\u00a0A colleague, David Scheschkewitz, pointed me to the article. We both independently analyzed different aspects, and first David, and then I then submitted separate articles for publication describing what we had found. Science today published both David’s thoughts (DOI:10.1126\/science.1195752<\/a>) and also those of another independent group, Igor Alabugin and colleagues (DOI:\u00a010.1126\/science.1196188<\/a>). The original authors have in turn responded (DOI:\u00a010.1126\/science.1195846<\/a>). My own article on the topic will appear very shortly (DOI:\u00a010.1039\/C0CC04023A<\/a>). You can see quite a hornet’s nest has been stirred up!<\/p>\n

At issue is whether the two bonds (indicated with arrows below) are best described as normally covalent, or very much weaker van der Waals contacts, or essentially non-interacting atoms. The last two interpretations would sustain the claim that 1,3-dimethyl cyclobutadiene\u00a0and\u00a0carbon dioxide can co-exist as separate species inside the cavity. The first would argue that they have reacted to form a different molecule.\u00a0You can inspect the 3D coordinates<\/a> by clicking on the diagram below.<\/p>\n

\"\"

Reported X-Ray structure. Click for 3D<\/p><\/div>Barboiu et al<\/em> originally argued that these two bonds were strong<\/em> van der Waals contacts, with C-C and C-O distances of 1.5 and 1.6\u00c5 respectively, and with a OCO angle of \u00a0120\u00b0. The various responses to this claim tend to the view that these distances\/angles clearly represent new covalent (or partially ionic-covalent) bonds, and that the combined species cannot<\/strong> be described as 1,3-dimethyl cyclobutadiene\u00a0and\u00a0carbon dioxide. There is obviously much more to it than that (including a detailed analysis of the errors present in a partially disordered crystal structure). So make your own minds up<\/a> based on the articles cited above and if it helps, the \u00a0original 3D coordinates, for your convenience made available above!<\/p>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

On 8th August this year, I posted on a fascinating article that had just appeared in Science (DOI:\u00a010.1126\/science.1188002), in which the crystal structure was reported of two small molecules,\u00a01,3-dimethyl cyclobutadiene\u00a0and\u00a0carbon dioxide, entrapped together inside a calixarene cavity. Other journals (e.g.\u00a0Nature Chemistry, DOI:\u00a010.1038\/nchem.823) ran the article as a research highlight (where the purpose is not a […]<\/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,"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],"tags":[124,196,1526,1529,615,389],"class_list":["post-2828","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-david-scheschkewitz","tag-igor-alabugin","tag-interesting-chemistry","tag-pericyclic","tag-watoc11","tag-x-ray"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-JC","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/2828","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=2828"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/2828\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2828"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2828"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2828"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}