{"id":20010,"date":"2018-08-22T15:17:16","date_gmt":"2018-08-22T14:17:16","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=20010"},"modified":"2022-09-24T13:13:46","modified_gmt":"2022-09-24T12:13:46","slug":"tetrahedral-carbon-and-cyclohexane","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=20010","title":{"rendered":"Tetrahedral carbon and cyclohexane."},"content":{"rendered":"
\n

Following the general recognition of carbon as being tetrahedrally tetravalent in 1869 (Paterno) and 1874 (Van’t Hoff and Le Bell), an early seminal exploitation of this to the conformation of cyclohexane was by Hermann Sachse<\/a> in 1890.[1]<\/a><\/span> This was\u00a0verified when the Braggs in 1913[2]<\/a><\/span>, followed by an oft-cited article by Mohr in 1918,[3]<\/a><\/span> established the crystal structure of diamond as comprising repeating rings in the chair conformation.\u2020<\/sup> So by 1926, you might imagine that the shape (or conformation as we would now call it) of cyclohexane would be well-known. No quite so for everyone!<\/p>\n

When The Journal of the Imperial College Chemical Society (<\/em>Volume 6) was brought to my attention<\/a>, I found an article by R. F Hunter;\"\"<\/a><\/p>\n

He proceeds to argue as follows:<\/p>\n

    \n
  1. The natural angle subtended at a tetrahedral carbon is 109.47\u00b0.<\/li>\n
  2. “The internal angle between the carbon to carbon valencies of a six-membered ring cyclohexane will, if the ring is uniplanar<\/span>, be … 120\u00b0.<\/em><\/li>\n
  3. “When the cyclohexane ring is prepared … we must therefore have the pushing apart of two of the valencies”.<\/li>\n
  4. The object of the experiments commenced in this College in 1914 was “to find what effect the pushing apart of the valencies …must have on the angle between the remaining pair of valencies<\/em>“.<\/li>\n
  5. You do wonder then why the assumption highlighted in red above was never really questioned during the twelve-year period of investigating angles around tetrahedral carbon.<\/li>\n<\/ol>\n

    The article itself is quite long, reporting the synthesis of many compounds in search of the postulated effect. Of course around twenty years later, Derek Barton used the by then generally accepted conformation of cyclohexane to explain reactivity in what become known as the theory of conformational analysis.<\/p>\n

    These two articles dating from 1926, and probably thought lost to science, show how some ideas can take decades to have any influence, whilst others can take root very much more quickly.<\/p>\n

    \n

    Postscript added in 2022<\/b>. In the news recently has been Lonsdaleite<\/a>, another allotrope of carbon. The saturated diamond structure has all the tetrahedral carbon forming six-membered rings in the chair<\/b>\u2020<\/sup> conformation. In Lonsdaleite<\/a>,[4]<\/a><\/span> there are boat as well as chair rings!
    \n\"\"<\/p>\n

    \"\"<\/p>\n

    \n

    \u2020<\/sup>The chair cyclohexane structure is easily discerned from Figure 7 in the Braggs’ paper![2]<\/a><\/span><\/p>\n

    References<\/h2>\n
    1. H. Sachse, \"Ueber die geometrischen Isomerien der Hexamethylenderivate\", Berichte der deutschen chemischen Gesellschaft<\/i>, vol. 23, pp. 1363-1370, 1890. https:\/\/doi.org\/10.1002\/cber.189002301216<\/a>\n\n<\/li>\n
    2. W.H. Bragg, and W.L. Bragg, \"The structure of the diamond\", Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character<\/i>, vol. 89, pp. 277-291, 1913. https:\/\/doi.org\/10.1098\/rspa.1913.0084<\/a>\n\n<\/li>\n
    3. E. Mohr, \"Die Baeyersche Spannungstheorie und die Struktur des Diamanten\", Journal f\u00fcr Praktische Chemie<\/i>, vol. 98, pp. 315-353, 1918. https:\/\/doi.org\/10.1002\/prac.19180980123<\/a>\n\n<\/li>\n
    4. F.P. Bundy, and J.S. Kasper, \"Hexagonal Diamond\u2014A New Form of Carbon\", The Journal of Chemical Physics<\/i>, vol. 46, pp. 3437-3446, 1967. https:\/\/doi.org\/10.1063\/1.1841236<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

      Following the general recognition of carbon as being tetrahedrally tetravalent in 1869 (Paterno) and 1874 (Van’t Hoff and Le Bell), an early seminal exploitation of this to the conformation of cyclohexane was by Hermann Sachse in 1890. This was\u00a0verified when the Braggs in 1913, followed by an oft-cited article by Mohr in 1918, established the […]<\/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,"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}},"categories":[4],"tags":[1440,48,1395,2476,2473,388,2477,46,179,2474,2472,1665,1442,2478,1560,2475],"ppma_author":[2661],"class_list":["post-20010","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry","tag-carbon","tag-chair","tag-chemistry","tag-conformation","tag-cycloalkanes","tag-cyclohexane","tag-cyclohexane-conformation","tag-derek-barton","tag-hermann-sachse","tag-hoff","tag-imperial-college-chemical-society","tag-isomerism","tag-physical-organic-chemistry","tag-r-f-hunter","tag-stereochemistry","tag-van-t-hof"],"yoast_head":"\nTetrahedral carbon and cyclohexane. - 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=20010\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Tetrahedral carbon and cyclohexane. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"Following the general recognition of carbon as being tetrahedrally tetravalent in 1869 (Paterno) and 1874 (Van’t Hoff and Le Bell), an early seminal exploitation of this to the conformation of cyclohexane was by Hermann Sachse in 1890. This was\u00a0verified when the Braggs in 1913, followed by an oft-cited article by Mohr in 1918, established the […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=20010\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2018-08-22T14:17:16+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2022-09-24T12:13:46+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2018\/08\/260-1024x347.jpg\" \/>\n<meta name=\"author\" content=\"Henry Rzepa\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Henry Rzepa\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Tetrahedral carbon and cyclohexane. - Henry Rzepa's Blog","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=20010","og_locale":"en_GB","og_type":"article","og_title":"Tetrahedral carbon and cyclohexane. - Henry Rzepa's Blog","og_description":"Following the general recognition of carbon as being tetrahedrally tetravalent in 1869 (Paterno) and 1874 (Van’t Hoff and Le Bell), an early seminal exploitation of this to the conformation of cyclohexane was by Hermann Sachse in 1890. 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By 1890, the structure of planar benzene was pretty much understood, but organic chemistry was still struggling somewhat to fully embrace three rather than two dimensions. A grand-old-man of organic chemistry at the time, Adolf von Baeyer,\u2026","rel":"","context":"In "General"","block_context":{"text":"General","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1"},"img":{"alt_text":"D6h to C2h for cyclohexane","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/01\/cx-c2h.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":9841,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=9841","url_meta":{"origin":20010,"position":1},"title":"The mysterious (aromatic) structure of n-Butyl lithium.","author":"Henry Rzepa","date":"March 17, 2013","format":false,"excerpt":"n-Butyl lithium is hexameric in the solid state and in cyclohexane solutions. Why? Here I try to find out some of its secrets. The crystal structure reveals the following points of interest: Six lithium atoms form a cluster with triangular faces. An off-centre carbanion caps a triangular lithium face. Four\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":"SUHBEC. CLICK FOR 3D.","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/03\/SUHBEC.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":3472,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=3472","url_meta":{"origin":20010,"position":2},"title":"A short history of molecular modelling: 1860-1890.","author":"Henry Rzepa","date":"February 5, 2011","format":false,"excerpt":"In 1953, the model of the DNA molecule\u00a0led to what has become regarded as the most\u00a0famous scientific diagram\u00a0of the 20th century. It had all started 93 years earlier in\u00a01860, at a time when the tetravalency of carbon was only just established (by William Odling) and the concept of atoms as\u2026","rel":"","context":"In "General"","block_context":{"text":"General","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/02\/molmod.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":7926,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=7926","url_meta":{"origin":20010,"position":3},"title":"Ring-flipping in cyclohexane in a different light","author":"Henry Rzepa","date":"October 12, 2012","format":false,"excerpt":"The conformational analysis of cyclohexane is a mainstay of organic chemistry. Is there anything new that can be said about it? Let us start with the diagram below: This identifies the start of the process as a chair conformation of cyclohexane, with D3d symmetry. I have highlighted a pair of\u2026","rel":"","context":"In \"chair\"","block_context":{"text":"chair","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?tag=chair"},"img":{"alt_text":"","src":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/10\/37.svg","width":350,"height":200},"classes":[]},{"id":1663,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=1663","url_meta":{"origin":20010,"position":4},"title":"Conformational analysis of cyclotriborazane","author":"Henry Rzepa","date":"February 14, 2010","format":false,"excerpt":"In an earlier post, I re-visited the conformational analysis of cyclohexane by looking at the vibrations of the entirely planar form (of D6h symmetry). The method also gave interesting results for the larger cyclo-octane ring. How about a larger leap into the unknown? Let us proceed as follows. One fun\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\/2010\/02\/B3N3H12.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":10220,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=10220","url_meta":{"origin":20010,"position":5},"title":"X-ray analysis and absolute configuration determination using porous complexes.","author":"Henry Rzepa","date":"April 17, 2013","format":false,"excerpt":"This is another in the occasional series of \"what a neat molecule\". In this case, more of a \"what a neat idea\". The s-triazine below, when coordinated to eg ZnI2, forms what is called a metal-organic-framework, or MOF. A recent article shows how such frameworks can be used to help\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":[]}],"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","0":null,"1":"","2":"","3":"","4":"","5":"","6":"","7":"","8":""}],"_links":{"self":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/20010","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=20010"}],"version-history":[{"count":30,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/20010\/revisions"}],"predecessor-version":[{"id":25632,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/20010\/revisions\/25632"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=20010"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=20010"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=20010"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=20010"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}