{"id":16889,"date":"2016-09-22T13:07:30","date_gmt":"2016-09-22T12:07:30","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=16889"},"modified":"2016-09-22T13:07:30","modified_gmt":"2016-09-22T12:07:30","slug":"more-stereoelectronics-galore-hexamethylene-triperoxide-diamine","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=16889","title":{"rendered":"More stereoelectronics galore: hexamethylene triperoxide diamine."},"content":{"rendered":"
\n

Compounds with O-O bonds often have weird properties. For example, artemisinin, which has some fascinating stereoelectronics<\/a>. Here is another such, recently in the news<\/a>\u00a0and\u00a0known as HMTD (hexamethylene triperoxide diamine).\u00a0The crystal structure was reported some time ago[1]<\/a><\/span> and the article included an inspection of the computed wavefunction. However this did not look at\u00a0the potential stereoelectronics in this species, which I\u00a0now address\u00a0here.<\/p>\n

\"hmtd\"<\/p>\n

A\u00a0\u03c9B97XD\/Def2-TZVPP calculation[2]<\/a><\/span> can be analysed for the NBO-derived interaction terms. This identifies an electron donor (normally a bond or a lone pair) and its E(2) perturbation energy interaction with an acceptor (normally an empty \u03c3*<\/sup> antibond). Here we are interested in the interaction between the nitrogen “lone pair” and the adjacent C-O\u00a0\u03c3*<\/sup>\u00a0antibond, of which there are six in the molecule due to the D3<\/sub> symmetry. E(2) is ~22.4 kcal\/mol, which is a large effect (the equivalent value for the so-called anomeric interaction between an oxygen lone pair and a C-O antibond is ~18 kcal\/mol). The effect of donation into the\u00a0empty C-O \u03c3*<\/sup>\u00a0antibond is to weaken it, unless the effect is balanced by a reciprocal interaction in the opposing direction, which is often the case in sugar-derived anomeric effects. Sugars of course are thermally relatively stable. In the case of HMTD, the reverse effect would be an oxygen Lp donating into the N-C\u00a0\u03c3*<\/sup>\u00a0antibond and this has the value of 14.5 kcal\/mol. Since the two are not balanced, this presumably contributes to the very unstable nature of this molecule.<\/p>\n

An alternative way of looking at what the electrons are up to is ELF,\u00a0a function based on the electron density which identifies the centroids of electron basins. The red arrows point to the four basins associated with the nitrogen “lone pair” (mostly the dumb-bell-shaped p-atomic orbital, hence four basins), and the integration being 3.2e for each nitrogen. This is a rather odd number for a “lone pair”. There is undoubtedly something unusual about this wavefunction which has yet to be identified.<\/p>\n

\"elf\"<\/p>\n

Finally, I ask how common the N(sp3<\/sup>)-C(sp3<\/sup>)-O-O structure motif might be?\u00a0In fact the Cambridge structure database has 81 entries! The scatterplot below includes 51 of them (no disorder, no errors, R<0.05). No clear-cut conclusions emerge from these statistics, except just a hint that as the C-O distance gets longer, the N-C distance might get shorter and that shorter N-C lengths\u00a0are associated with shorter O-O lengths.<\/p>\n

\"elf1\"<\/p>\n

 <\/p>\n

 <\/p>\n

 <\/p>\n

References<\/h2>\n
  1. A. Wierzbicki, E.A. Salter, E.A. Cioffi, and E.D. Stevens, \"Density Functional Theory and X-ray Investigations of P- and M-Hexamethylene Triperoxide Diamine and Its Dialdehyde Derivative\", The Journal of Physical Chemistry A<\/i>, vol. 105, pp. 8763-8768, 2001. https:\/\/doi.org\/10.1021\/jp0123841<\/a>\n\n<\/li>\n
  2. H. Rzepa, \"HMTD Hexamethylenetriperoxidediamine D3 NBO\", 2016. https:\/\/doi.org\/10.14469\/hpc\/1663<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    Compounds with O-O bonds often have weird properties. For example, artemisinin, which has some fascinating stereoelectronics. Here is another such, recently in the news\u00a0and\u00a0known as HMTD (hexamethylene triperoxide diamine).\u00a0The crystal structure was reported some time ago and the article included an inspection of the computed wavefunction. However this did not look at\u00a0the potential stereoelectronics in […]<\/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],"tags":[1857,1859,1416,1453,1872,1491,1889,1820,1893,1903],"class_list":["post-16889","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-amines","tag-artemisinin","tag-chemistry","tag-functional-groups","tag-hexamethylene-triperoxide-diamine","tag-organic-chemistry","tag-organic-peroxides","tag-peroxide","tag-perturbation-energy-interaction","tag-stereoelectronics"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-4op","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/16889","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=16889"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/16889\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=16889"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=16889"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=16889"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}