{"id":27055,"date":"2024-05-20T15:01:15","date_gmt":"2024-05-20T14:01:15","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=27055"},"modified":"2024-05-20T15:01:15","modified_gmt":"2024-05-20T14:01:15","slug":"possible-formation-of-an-impossible-molecule","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=27055","title":{"rendered":"Possible Formation of an Impossible Molecule?"},"content":{"rendered":"
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In the previous post<\/a>, I explored the so-called “impossible” molecule methanetriol. It is regarded as such because the equilbrium resulting in loss of water is very facile, being exoenergic by ~14 kcal\/mol in free energy. Here I explore whether changing the substituent\u00a0R could result in suppressing the loss of water and stabilising the triol.
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\nI started (as I usually do) with a search for crystal structures, in this case containing the motif shown below (trisubstituted carbon, disubstituted oxygen and \u00a0R = H or C and any type of connecting bond), which is the species resulting from loss of R–<\/sup> to form a trihydroxycarbenium cation.
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This produces six hits, of which \u00a0HIWQEJ[1]<\/a><\/span> (DOI: 10.5517\/cc3k560<\/a>) and UYOYUD[2]<\/a><\/span> (DOI: 10.5517\/ccvrghj<\/a>) are both salts of trihydroxycarbenium cation (or protonated carbonic acid) itself – the counter\u00a0ion being eg AsF6<\/sub> or an iron system. So R needs to be a stable anion and two obvious groups are triflate (trifluoromethylsulfonate) or bis(trifluoromethanesulfonyl)azanide.<\/p>\n

The triflate (R=CF3<\/sub>SO2<\/sub>-O) shown below has an unusually long predicted C-O bond (1.620\u00c5), which suggests the system is already partially ionised as shown in the top diagram. An \u03c9B97X-D calculation [3]<\/a><\/span>, DOI: 10.14469\/hpc\/14280<\/a>) reveals the species shown below is +6.6 kcal\/mol higher in free energy than the one corresponding to loss of water.<\/p>\n

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\nBis-triflamide (bis(trifluoromethanesulfonyl)azanide) goes further, helped no doubt by the formation of a second strong hydrogen bond between the two ions. It is now -11.8 kcal\/mol lower in free energy compared to the species resulting from loss of water.<\/p>\n

\"\"<\/p>\n

So that is my candidate for a “possible”\u00a0impossible molecule. Any takers for its synthesis?<\/p>\n

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Postscript:<\/b> The next higher homologue, tris(trifluoromethanesulfonyl)methanide anion + trihydroxycarbenium cation is similar to the bis-triflamide in being -12.1 kcal\/mol lower than the species resulting from loss of water. <\/p>\n

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References<\/h2>\n
  1. R. Minkwitz, and S. Schneider, \"Trihydroxycarbenium Hexafluorometalates: Salts of Protonated Carbonic Acid\", Angewandte Chemie International Edition<\/i>, vol. 38, pp. 714-715, 1999. https:\/\/doi.org\/10.1002\/(sici)1521-3773(19990301)38:5<714::aid-anie714>3.0.co;2-k<\/a>\n\n<\/li>\n
  2. S. Guo, J. Lin, W. Chen, X. Wei, J. Wang, and W. Dong, \"CCDC 797118: Experimental Crystal Structure Determination\", 2011. https:\/\/doi.org\/10.5517\/ccvrghj<\/a>\n\n<\/li>\n
  3. H. Rzepa, \"Possible Formation of an Impossible Molecule?\", 2024. https:\/\/doi.org\/10.14469\/hpc\/14280<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    In the previous post, I explored the so-called “impossible” molecule methanetriol. It is regarded as such because the equilbrium resulting in loss of water is very facile, being exoenergic by ~14 kcal\/mol in free energy. Here I explore whether changing the substituent\u00a0R could result in suppressing the loss of water and stabilising the triol. I […]<\/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":[1],"tags":[],"class_list":["post-27055","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-72n","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/27055","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=27055"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/27055\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=27055"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=27055"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=27055"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}