{"id":16646,"date":"2016-08-04T14:25:32","date_gmt":"2016-08-04T13:25:32","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=16646"},"modified":"2016-08-04T14:25:32","modified_gmt":"2016-08-04T13:25:32","slug":"stereoelectronic-effects-galore-bistrifluoromethyltrioxide","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=16646","title":{"rendered":"Stereoelectronic effects galore: bis(trifluoromethyl)trioxide."},"content":{"rendered":"
\n

Here is a little molecule that can be said to be pretty electron rich. There are lots of lone pairs present, and not a few electron-deficient \u03c3-bonds. I thought it might be fun to look at the stereoelectronic interactions set up in this little system.<\/p>\n

\"Trioxide\"<\/p>\n

Known as ZEYDOW in the crystal structure database[1]<\/a><\/span> (this species has a melting point of -138C, and its no trivial matter to measure x-ray diffraction of such a crystal!);\u00a0a\u00a0\u03c9B97XD\/Def2-TZVPP calculation is used to quantify the electron density [2]<\/a><\/span> and this is then subjected to localisation using the ELF function. The little purple spheres represent so-called monosynaptic electron basins, or lone pairs as we might rather loosely call them (pair is not always an accurate term).\u00a0<\/p>\n

\"zeydow\"<\/p>\n

How these “lone pairs” act as electron donors into empty \u03c3*<\/sup> acceptors can be quantified using NBO theory. The following table shows as many as 24<\/strong> strong interactions (> 10 kcal\/mol). \u00a0This now augments my previous post on “Anomeric effects at carbon involving lone pairs originating from one or two nitrogens<\/a>” and represents an example of “Anomeric effects at oxygen<\/strong> involving lone pairs originating from oxygen”.<\/p>\n

The final two entries originate from lone pairs on the central oxygen, donating approximately antiperiplanar (~160\u00b0) into the O-CF3<\/sub>\u00a0antibonds, but with only a low value of the E(2) interaction energy. These two lone pairs are curiously inert.<\/p>\n\n\n\n\n\n\n\n\n
Lone pair donor<\/th>\n\u03c3-acceptor<\/th>\nNBO E(2) energy<\/th>\n<\/tr>\n
On F: 16,17,18,19,25,35,36,39,40,41,43,45<\/td>\nC-F<\/td>\n18-20<\/td>\n<\/tr>\n
On F: 26,34,37,39,42,44<\/td>\nC-O<\/td>\n11-18<\/td>\n<\/tr>\n
On O: 27,28,24,33<\/td>\nC-F<\/td>\n13-16<\/td>\n<\/tr>\n
On O: 27,33<\/td>\nC-O<\/td>\n13<\/td>\n<\/tr>\n
On O: 30,31<\/td>\nC-O<\/td>\n3.5<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Apart from this curious molecule, there are few other examples of the R-O-O-O-R functional group,[3]<\/a><\/span> but this one did catch my eye,[4]<\/a><\/span> largely because it was retrieved from a search specification of R-O-O-O-R. The central oxygen apparently supports six O-O bonds, as well as three hydrogens. It is nothing of the sort of course. Reading the text reveals it is really three O…H-O bonds, disordered into two equally probable positions. There are no O-O bonds present at all, which reminds us we must always subject structures derived from x-ray crystallography to a chemical reality check.
\n \"yocsis\"<\/p>\n

References<\/h2>\n
  1. K.I. Gobbato, H. Oberhammer, M.F. Klapdor, D. Mootz, W. Poll, S.E. Ulic, and H. Willner, \"Bis(trifluoromethyl)trioxide: First Structure of a Straight\u2010Chain Trioxide\", Angewandte Chemie International Edition in English<\/i>, vol. 34, pp. 2244-2245, 1995. https:\/\/doi.org\/10.1002\/anie.199522441<\/a>\n\n<\/li>\n
  2. H.S. Rzepa, \"C 2 F 6 O 3\", 2016. https:\/\/doi.org\/10.14469\/ch\/195291<\/a>\n\n<\/li>\n
  3. Pernice, H.., Berkei, M.., Henkel, G.., Willner, H.., Arguello, G.A.., McKee, M.L.., and Webb, T.R.., \"CCDC 224327: Experimental Crystal Structure Determination\", 2004. https:\/\/doi.org\/10.5517\/cc7jfcj<\/a>\n\n<\/li>\n
  4. J.L. Atwood, S.G. Bott, P.C. Junk, and M.T. May, \"Liquid clathrate media containing transition metal halocarbonyl anions; formation and crystal structures of [K+ \u00b7 18-crown-6][Cr(CO)5Cl], [H3O+ \u00b7 18-crown-6][W(CO)5Cl], [H3O+ \u00b7 18-crown-6][W(CO)4Cl3], and [H2O \u00b7 bis-aza-18-crown-6 \u00b7 (H+)2][W(CO)4Cl3]2\", Journal of Organometallic Chemistry<\/i>, vol. 487, pp. 7-15, 1995. https:\/\/doi.org\/10.1016\/0022-328x(94)05072-j<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    Here is a little molecule that can be said to be pretty electron rich. There are lots of lone pairs present, and not a few electron-deficient \u03c3-bonds. I thought it might be fun to look at the stereoelectronic interactions set up in this little system. Known as ZEYDOW in the crystal structure database (this species […]<\/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":[1754,6],"tags":[510,1855,1838,389],"class_list":["post-16646","post","type-post","status-publish","format-standard","hentry","category-crystal_structure_mining","category-interesting-chemistry","tag-chemical-bonding","tag-sigma-bond","tag-stereoelectronic-effect","tag-x-ray"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-4ku","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/16646","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=16646"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/16646\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=16646"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=16646"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=16646"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}