{"id":29410,"date":"2025-08-13T10:46:47","date_gmt":"2025-08-13T09:46:47","guid":{"rendered":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=29410"},"modified":"2025-08-13T10:46:47","modified_gmt":"2025-08-13T09:46:47","slug":"energy-decomposition-analysis-of-hindered-alkenes-tetra-t-butylethene-and-others","status":"publish","type":"post","link":"https:\/\/rzepa.net\/blog\/2025\/08\/13\/energy-decomposition-analysis-of-hindered-alkenes-tetra-t-butylethene-and-others\/","title":{"rendered":"Energy decomposition analysis of hindered alkenes: Tetra t-butylethene and others."},"content":{"rendered":"

In the previous post,[cite]10.59350\/rzepa.29383[\/cite] I introduced the N=N double bond in nitrosobenzene dimer, arguing that even though it was a formal double bond, its bond dissociation energy made it nonetheless a very weak double bond! This was backed up by a technique known as energy decomposition analysis or EDA. Here I use a variant of this method \u00a0known as \u00a0NEDA to look at some other strained alkenes, including the famously non-existent tetra t-Butyl ethene.<\/p>\n

\"\"<\/a><\/p>\n

The NEDA procedure gives a fragment interaction energy (decomposing it into fundamental quantum mechanically derived energies if required) with respect to a reference state for the fragments. In this case, the fragments are obtained by cutting the double bond, resulting in triplet state carbenes as the reference state. The calculations (B3LYP+GD3+BJ\/Def2-TZVPP) are available here.[cite]10.14469\/hpc\/15463[\/cite]<\/p>\n

    \n
  1. Compound 1<\/strong>, a relatively unstrained alkene, \u0394E = -177.0 kcal\/mol<\/strong>, RCC<\/sub> 1.341\u00c5<\/li>\n
  2. Compound 2<\/strong> (PUVQUE, [cite]10.1107\/S0108270198099247[\/cite], [cite]10.5517\/cc4cx7m[\/cite]), \u0394E = -164.3 kcal\/mol,<\/strong> RCC<\/sub> 1.362\u00c5, CC torsion 16.5\u00b0<\/li>\n
  3. Compound 3<\/strong> (CUBVOK, [cite]10.1016\/S0040-4039(00)98504-6[\/cite]) \u0394E = -167.9 kcal\/mol,<\/strong> RCC<\/sub> 1.351\u00c5, CC torsion 9.2\u00b0<\/li>\n
  4. Compound 4<\/strong> (currently unknown) \u0394E = -135.8 kcal\/mol<\/strong>, RCC<\/sub> 1.380\u00c5, CC torsion 54.5\u00b0<\/li>\n<\/ol>\n

    The NEDA interaction energy is directly proportional to both the CC bond length and the C-C=C-C torsion angle. What is interesting however is the large interaction energy gap in \u0394E between the two known hindered alkenes (2<\/strong> and 3<\/strong>)\u00a0and the unknown tetra-t-butyl ethene 4<\/strong>. It seems moving from say compound 2<\/strong> by converting the two iso-propyl substituents to full t-butyl ones is just too large a change to bridge. Unless one day isolated as a very very unstable species, compound 4<\/strong> seems destined not to exist!<\/p>\n

    \n

    This post has DOI: 10.59350\/rzepa.29410<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    In the previous post,[cite]10.59350\/rzepa.29383[\/cite] I introduced the N=N double bond in nitrosobenzene dimer, arguing that even though it was a formal double bond, its bond dissociation energy made it nonetheless a very weak double bond! This was backed up by a technique known as energy decomposition analysis or EDA. Here I use a variant of […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-29410","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry"],"_links":{"self":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/posts\/29410","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/comments?post=29410"}],"version-history":[{"count":0,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/posts\/29410\/revisions"}],"wp:attachment":[{"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/media?parent=29410"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/categories?post=29410"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rzepa.net\/blog\/wp-json\/wp\/v2\/tags?post=29410"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}