{"id":8375,"date":"2012-11-25T09:21:03","date_gmt":"2012-11-25T09:21:03","guid":{"rendered":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=8375"},"modified":"2012-12-29T17:17:04","modified_gmt":"2012-12-29T17:17:04","slug":"the-regiospecificity-of-di-imide-reduction-of-an-alkene","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8375","title":{"rendered":"The regiospecificity of di-imide reduction of an alkene."},"content":{"rendered":"
\n

Not a few posts on this blog dissect the mechanisms of well known text-book reactions. But one reaction type where there are few examples on these pages are reductions. These come in three types; using electrons, using a hydride anion and using di-hydrogen. Here I first take a closer look at the third type, and in particular di-hydrogen as\u00a0delivered from di-imide<\/a>.<\/p>\n

\"\"<\/p>\n

This reagent tends to be specific for terminal (less highly substituted) double bonds[1]<\/a><\/span>. Two\u00a0\u03c9B97XD\/6-311G(d,p)<\/a> calculations<\/a> predicts a free energy discrimination of 2.85 kcal\/mol for the two double bonds in the system above, which works out as a ratio of 125:1 in favour of the less substituted system. The Wiberg bond orders of the two forming C-H bonds indicate that at the transition state\u00a0the one to the less substituted terminal carbon is more highly formed (0.234) than the one to the more substituted carbon (0.198). The NICS(0) magnetic index of aromaticity at the ring critical point \u00a0(centroid) of the pericyclic participating atoms has a value of -22.2 ppm, which indicates a significant diamagnetic ring current indicative of a (\u03c3-aromatic) transition state. The two transferring hydrogens have predicted “aromatic” shifts of 11.6 and 10.5 ppm.<\/p>\n

\"\"

Transition state for di-hydrogen transfer. Click for 3D.<\/p><\/div>\n\n\n\n\n
\"\"<\/td>\n<\/tr>\n
\"\"<\/td>\n\"\"<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The intrinsic reaction coordinate<\/a> (IRC) shows two distinct phases:<\/p>\n

    \n
  1. From IRC 3 to -3, it represents a pericyclic process, involving an (aromatic) transition state in which the six atoms involved are all co-planar.<\/li>\n
  2. From IRC -4 however, the newly reduced C-C bond starts to rotate to change the conformation from syn-planar to gauche. This rotation only comes at the very end of the reaction.<\/li>\n<\/ol>\n

    No real surprises here then, but it is useful to know that the regiospecificity of such reactions can apparently be well predicted.<\/p>\n

    References<\/h2>\n
    1. C. Smit, M.W. Fraaije, and A.J. Minnaard, \"Reduction of Carbon\u2212Carbon Double Bonds Using Organocatalytically Generated Diimide\", The Journal of Organic Chemistry<\/i>, vol. 73, pp. 9482-9485, 2008. https:\/\/doi.org\/10.1021\/jo801588d<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

      Not a few posts on this blog dissect the mechanisms of well known text-book reactions. But one reaction type where there are few examples on these pages are reductions. These come in three types; using electrons, using a hydride anion and using di-hydrogen. Here I first take a closer look at the third type, and […]<\/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_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":[],"tags":[948,2650,843,373],"ppma_author":[2661],"class_list":["post-8375","post","type-post","status-publish","format-standard","hentry","tag-free-energy-discrimination","tag-pericyclic","tag-reaction-mechanism","tag-tutorial-material"],"yoast_head":"\nThe regiospecificity of di-imide reduction of an alkene. - 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=8375\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"The regiospecificity of di-imide reduction of an alkene. - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"Not a few posts on this blog dissect the mechanisms of well known text-book reactions. But one reaction type where there are few examples on these pages are reductions. These come in three types; using electrons, using a hydride anion and using di-hydrogen. Here I first take a closer look at the third type, and […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8375\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2012-11-25T09:21:03+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2012-12-29T17:17:04+00:00\" \/>\n<meta property=\"og:image\" content=\"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/11\/diimide.svg\" \/>\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":"The regiospecificity of di-imide reduction of an alkene. - 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=8375","og_locale":"en_GB","og_type":"article","og_title":"The regiospecificity of di-imide reduction of an alkene. - Henry Rzepa's Blog","og_description":"Not a few posts on this blog dissect the mechanisms of well known text-book reactions. But one reaction type where there are few examples on these pages are reductions. These come in three types; using electrons, using a hydride anion and using di-hydrogen. Here I first take a closer look at the third type, and […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8375","og_site_name":"Henry Rzepa's Blog","article_published_time":"2012-11-25T09:21:03+00:00","article_modified_time":"2012-12-29T17:17:04+00:00","og_image":[{"url":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/11\/diimide.svg","type":"","width":"","height":""}],"author":"Henry Rzepa","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Henry Rzepa","Estimated reading time":"2 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8375#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8375"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"The regiospecificity of di-imide reduction of an alkene.","datePublished":"2012-11-25T09:21:03+00:00","dateModified":"2012-12-29T17:17:04+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8375"},"wordCount":309,"commentCount":2,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8375#primaryimage"},"thumbnailUrl":"http:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2012\/11\/diimide.svg","keywords":["free energy discrimination","pericyclic","Reaction Mechanism","Tutorial material"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8375#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8375","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=8375","name":"The regiospecificity of di-imide reduction of an alkene. - 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This indicated, like most thermal pericyclic reactions, an\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\/11\/GaussViewScreenSnapz004.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":31140,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=31140","url_meta":{"origin":8375,"position":1},"title":"The fast disappearance of hydroxycarbene through hydrogen tunnelling – or is it really tunnelling?","author":"Henry Rzepa","date":"April 11, 2026","format":false,"excerpt":"In 2008, the previously elusive hydroxycarbene, H-C-OH was finally reported as having been captured by matrix isolation, accompanied by the observation that \"we unexpectedly find that H\u2013C\u2013OH rearranges to formaldehyde with a half-life of only 2h at 11K by pure hydrogen tunnelling through a large energy barrier in excess of\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":26997,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=26997","url_meta":{"origin":8375,"position":2},"title":"Exploring Methanetriol – “the Formation of an Impossible Molecule”","author":"Henry Rzepa","date":"May 16, 2024","format":false,"excerpt":"What constitutes an \"impossible molecule\"? Well, here are two, the first being the topic of a recent article. The second is a favourite of organic chemistry tutors, to see if their students recognise it as an unusual (= impossible) form of a much better known molecule. Perhaps we could define\u2026","rel":"","context":"With 2 comments","block_context":{"text":"With 2 comments","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=26997#comments"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2024\/05\/COLRUT.gif?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":16118,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=16118","url_meta":{"origin":8375,"position":3},"title":"Hydronium hydroxide: the why of pH 7.","author":"Henry Rzepa","date":"April 14, 2016","format":false,"excerpt":"Ammonium hydroxide (NH4+...OH-) can be characterised quantum mechanically when stabilised by water bridges connecting the ion-pairs. It is a small step from there to hydronium hydroxide, or H3O+...OH-. The measured concentrations [H3O+] \u2261 [OH-]\u00a0give\u00a0rise of course to the well-known\u00a0pH 7 of pure water, and converting this ionization constant to a\u2026","rel":"","context":"In "General"","block_context":{"text":"General","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":20576,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=20576","url_meta":{"origin":8375,"position":4},"title":"The shortest known CF…HO hydrogen bond.","author":"Henry Rzepa","date":"March 24, 2019","format":false,"excerpt":"There is a predilection amongst chemists for collecting records; one common theme is the length of particular bonds, either the shortest or the longest. A particularly baffling type of bond is that between the very electronegative F atom and an acid hydrogen atom such as that in OH. Thus short\u2026","rel":"","context":"In "crystal_structure_mining"","block_context":{"text":"crystal_structure_mining","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=1745"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2019\/03\/F-inter-300x189.png?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":5500,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=5500","url_meta":{"origin":8375,"position":5},"title":"The peroxidation of alkynes: things are not always what they seem.","author":"Henry Rzepa","date":"November 16, 2011","format":false,"excerpt":"The epoxidation of an alkene to give an oxirane is taught in introductory organic chemistry. Formulating an analogous mechanism for such reaction of an alkyne\u00a0sounds straightforward, but one gradually realises that it requires raiding knowledge from several other areas of (perhaps slightly more advanced) chemistry to achieve a joined up\u2026","rel":"","context":"In "Curly arrows"","block_context":{"text":"Curly arrows","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?cat=2327"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2011\/11\/1.gif?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","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\/8375","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=8375"}],"version-history":[{"count":18,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/8375\/revisions"}],"predecessor-version":[{"id":8838,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/8375\/revisions\/8838"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8375"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8375"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8375"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=8375"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}