{"id":24159,"date":"2021-08-17T13:49:20","date_gmt":"2021-08-17T12:49:20","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=24159"},"modified":"2021-08-17T14:04:06","modified_gmt":"2021-08-17T13:04:06","slug":"tetra-isopropylmethane-and-tetra-t-butylmethane","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=24159","title":{"rendered":"Tetra-isopropylmethane and tetra-t-butylmethane."},"content":{"rendered":"
\n

The homologous hydrocarbon series R4<\/sub>C is known for R=Me as neopentane and for R=Et as 3,3-diethylpentane. The next homologue, R=i<\/sup><\/em>Pr bis(3,3-isopropyl)-2,4-dimethylpentane is also a known molecule[1]<\/a><\/span> for which a crystal structure has been reported (DOI: https:\/\/doi.org\/10.5517\/cc4wvnh<\/a>). The final member of the series, R= t<\/sup>butyl is unknown. Here I have a look at some properties of the last two of these highly hindered hydrocarbons.<\/p>\n

First the non-covalent-interactions (NCI) analysis, for a \u03c9B97XD\/Def2-SVPP\/SCRF=dichloromethane wavefunction. This explores the properties of the weak electron density in the regions in between bonds, ie the non-bonded regions. In the presentation below, if that region is stabilizing, the surface is coloured cyan or dark green whereas if it is destabilising, it is pale green, yellow or orange.\u00a0<\/p>\n

\"\"<\/p>\n

The above for R=i<\/sup><\/em>Pr shows extensive but disconnected regions with NCI properties, with the pale cyan\/green ones stabilizing and the regions verging on yellow repulsive. It would not be easy to conclude that this molecule overall is stabilised by dispersion! The predicted 1<\/sup>H NMR spectrum shows only one methine environment (2.59 ppm) but three methyl ones at 1.51, 1.04 and 0.94 (1.16 av\/obs 2.23 and 1.04) ppm. The C-C bond lengths are 1.581\u00c5 (obs 1.599).<\/p>\n

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

The NCI for R = t<\/sup><\/em>butyl shows that the entire NCI surface is connected within the regions of the molecule, with far more green\/yellow than stabilizing cyan. This molecule, which has an unusual\u00a0T<\/strong> chiral symmetry is certainly sterically strained. The predicted C-C bond lengths of 1.668\u00c5 are unusually long (wB97XD\/Def2-TZVPP).<\/p>\n

\"\"<\/p>\n

The optical rotation (589nm) is -179\u00b0, which raises the question of whether it would be configurationally stable? The predicted 1<\/sup>H NMR shows three methyl environments (2.21, 1.92 and 0.44 ppm), averaging to 1.52ppm, which is significantly different from the isopropyl analogue.<\/p>\n

Tetra t-butylmethane is often cited as the smallest branched hydrocarbon that cannot be made.[2]<\/a><\/span>,[3]<\/a><\/span>,[4]<\/a><\/span> Certainly it looks far more strained than the isopropyl version. Its preparation is a challenge that might never be achieved!<\/p>\n

References<\/h2>\n
  1. S.I. Kozhushkov, R.R. Kostikov, A.P. Molchanov, R. Boese, J. Benet-Buchholz, P.R. Schreiner, C. Rinderspacher, I. Ghiviriga, and A. de Meijere, \"Tetracyclopropylmethane: A Unique Hydrocarbon with S4 Symmetry\", Angewandte Chemie International Edition<\/i>, vol. 40, pp. 180-183, 2001. https:\/\/doi.org\/10.1002\/1521-3773(20010105)40:1<180::aid-anie180>3.0.co;2-k<\/a>\n\n<\/li>\n
  2. K.M. Nalin de Silva, and J.M. Goodman, \"What Is the Smallest Saturated Acyclic Alkane that Cannot Be Made?\", Journal of Chemical Information and Modeling<\/i>, vol. 45, pp. 81-87, 2004. https:\/\/doi.org\/10.1021\/ci0497657<\/a>\n\n<\/li>\n
  3. M. Cheng, and W. Li, \"Structural and Energetics Studies of Tri- and Tetra-<i>tert<\/i>-butylmethane\", The Journal of Physical Chemistry A<\/i>, vol. 107, pp. 5492-5498, 2003. https:\/\/doi.org\/10.1021\/jp034879r<\/a>\n\n<\/li>\n
  4. N.L. Allinger, J. Lii, and H.F. Schaefer, \"Molecular Mechanics (MM4) Studies on Unusually Long Carbon\u2013Carbon Bond Distances in Hydrocarbons\", Journal of Chemical Theory and Computation<\/i>, vol. 12, pp. 2774-2778, 2016. https:\/\/doi.org\/10.1021\/acs.jctc.5b00926<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    The homologous hydrocarbon series R4C is known for R=Me as neopentane and for R=Et as 3,3-diethylpentane. The next homologue, R=iPr bis(3,3-isopropyl)-2,4-dimethylpentane is also a known molecule for which a crystal structure has been reported (DOI: https:\/\/doi.org\/10.5517\/cc4wvnh). The final member of the series, R= tbutyl is unknown. Here I have a look at some properties of […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"activitypub_content_warning":"","activitypub_content_visibility":"","activitypub_max_image_attachments":5,"activitypub_interaction_policy_quote":"anyone","activitypub_status":"","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},"jetpack_post_was_ever_published":false},"categories":[4],"tags":[],"ppma_author":[2661],"class_list":["post-24159","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry"],"yoast_head":"\nTetra-isopropylmethane and tetra-t-butylmethane. - Henry Rzepa's Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=24159\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Tetra-isopropylmethane and tetra-t-butylmethane. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"The homologous hydrocarbon series R4C is known for R=Me as neopentane and for R=Et as 3,3-diethylpentane. The next homologue, R=iPr bis(3,3-isopropyl)-2,4-dimethylpentane is also a known molecule for which a crystal structure has been reported (DOI: https:\/\/doi.org\/10.5517\/cc4wvnh). The final member of the series, R= tbutyl is unknown. 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The next homologue, R=iPr bis(3,3-isopropyl)-2,4-dimethylpentane is also a known molecule for which a crystal structure has been reported (DOI: https:\/\/doi.org\/10.5517\/cc4wvnh). The final member of the series, R= tbutyl is unknown. 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Whilst it has a classical structure describable by a combination of Lewis-style two electron and four electron bonds, its NMR behaviour reveals it to be highly fluxional. This means that even at low temperatures, the position of these two-electron bonds rapidly shifts in the equilibrium\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/09\/CAZFUE1.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":18897,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=18897","url_meta":{"origin":24159,"position":1},"title":"Dispersion-induced triplet aromatisation?","author":"Henry Rzepa","date":"January 3, 2019","format":false,"excerpt":"There is emerging interest in cyclic conjugated molecules that happen to have triplet spin states and which might be expected to follow a 4n rule for aromaticity. The simplest such system would be the triplet state of cyclobutadiene, for which a non or anti-aromatic singlet state is always found to\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/01\/CBD-1024x717.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":29410,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=29410","url_meta":{"origin":24159,"position":2},"title":"Energy decomposition analysis of hindered alkenes: Tetra t-butylethene and others.","author":"Henry Rzepa","date":"August 13, 2025","format":false,"excerpt":"In the previous post, 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\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":7721,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=7721","url_meta":{"origin":24159,"position":3},"title":"Predicted properties of a candidate for a frozen semibullvalene.","author":"Henry Rzepa","date":"September 17, 2012","format":false,"excerpt":"I am following up on one unfinished thread in my previous post; a candidate was proposed in which the transition state for [3,3] sigmatropic rearrangement in a semibullvalene might be frozen out to become instead a stable minimum. The hypothesis was that such a species would be aromatic, a bis-homoaromatic\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/09\/dicyano-diaza-aim.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":16441,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=16441","url_meta":{"origin":24159,"position":4},"title":"An alternative mechanism for nucleophilic substitution at silicon using a tetra-alkyl ammonium fluoride.","author":"Henry Rzepa","date":"May 27, 2016","format":false,"excerpt":"In the previous post, I explored the mechanism for nucleophilic substitution at a silicon centre proceeding via retention of configuration involving a Berry-like pseudorotation.\u00a0Here\u00a0I probe an alternative route involving inversion of configuration at the Si centre. Both stereochemical modes are known to occur, depending on the leaving group, solvent and\u2026","rel":"","context":"In "reaction mechanism"","block_context":{"text":"reaction mechanism","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1086"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":8961,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8961","url_meta":{"origin":24159,"position":5},"title":"The mechanism of the Benzidine rearrangement.","author":"Henry Rzepa","date":"January 6, 2013","format":false,"excerpt":"The benzidine rearrangement is claimed to be an example of the quite rare\u00a0[5,5] sigmatropic migration, which is a ten-electron homologation of the very common [3,3] sigmatropic reaction (e.g. the Cope or Claisen). Some benzidine rearrangements are indeed thought to go through the [3,3] route. The topic has been reviewed here.\u2026","rel":"","context":"In "Interesting chemistry"","block_context":{"text":"Interesting chemistry","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=4"},"img":{"alt_text":"NCI surface. Click for 3D.","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/01\/benzidinenci.jpg?resize=350%2C200","width":350,"height":200},"classes":[]}],"jetpack_likes_enabled":false,"authors":[{"term_id":2661,"user_id":1,"is_guest":0,"slug":"admin","display_name":"Henry Rzepa","avatar_url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","author_category":"1","first_name":"Henry","last_name":"Rzepa","user_url":"https:\/\/orcid.org\/0000-0002-8635-8390","job_title":"","description":"Henry Rzepa is Emeritus Professor of Computational Chemistry at Imperial College London."}],"_links":{"self":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/24159","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=24159"}],"version-history":[{"count":36,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/24159\/revisions"}],"predecessor-version":[{"id":24207,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/24159\/revisions\/24207"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=24159"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=24159"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=24159"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=24159"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}