{"id":23044,"date":"2020-11-28T08:23:52","date_gmt":"2020-11-28T08:23:52","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=23044"},"modified":"2020-12-02T09:55:34","modified_gmt":"2020-12-02T09:55:34","slug":"is-cyanogen-chloride-fluoride-a-source-of-cn","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044","title":{"rendered":"Is cyanogen chloride (fluoride) a source of C\u2a78N(+)?"},"content":{"rendered":"
\n

In 2010 I recounted the story<\/a> of an organic chemistry tutorial, in which I asked the students the question “how would you synthesize 3-nitrobenzonitrile<\/em>“.
\n\"\"<\/a><\/p>\n

The expected answer was to generate a nitronium ion to nitrate benzonitrile, but can one invert this by generating a C\u2a78N+<\/sup> ion to cyanate nitrobenzene? The students were then invited to generate a valence bond structure for C\u2a78N+<\/sup> and I showed them the possibility that it might contain a quadruple bond to the carbon. Ten years later, Mike Turner in a comment on that post<\/a> revealed an article dating from 1960[1]<\/a><\/span> in which cyanogen fluoride was studied. There, in an innocuous comment, they state “Cyanogen fluoride, like cyanogen chloride, re-acted with benzene in the presence of aluminum chloride to form benzonitrile in 20% conversion<\/em><\/strong>“. Here I explore whether this reagent really can be a source of free C\u2a78N+<\/sup>.<\/p>\n

Calculations at the \u03c9B97XD\/Def2-TZVPP\/SCRF=water level (FAIR Data DOI: 10.14469\/hpc\/7584<\/a>)\u00a0were conducted to explore the possible energetics of using ClCN to electrophilically cyanate benzene. Firstly, the energy of the separated ion pair AlCl4<\/sub>–<\/sup>.C\u2a78N+<\/sup> is 190.9 kcal\/mol higher than the neutral reagents AlCl3<\/sub>.ClCN, which makes the formation of free C\u2a78N+<\/sup> unlikely. So what about a concerted process, in which benzene as a nucleophile attacks ClCN with the help of AlCl3<\/sub>? This would be a 1,1-substitution reaction at an sp-carbon centre. \"\"<\/a><\/p>\n

The free energy barrier for this bimolecular process is 46.4 kcal\/mol. It is along the right lines, but still about 20 kcal\/mol too high for a facile thermal process.\"\"<\/a><\/p>\n

In an effort to improve the model and hence reduce this barrier, the dimeric reagent Al2<\/sub>Cl6<\/sub> was tried instead. The final free energy barrier was 48.5 kcal\/mol.<\/p>\n

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

So to conclude, generating free C\u2a78N+<\/sup> is very unlikely. But cyanogen chloride can act as a C\u2a78N+<\/sup> “delivery agent” via<\/em> a bimolecular route. There remains a mystery however. The free energy barriers for our two models are too high to accomplish facile cyanation of benzene. There must be another mechanism, as of yet unexplored, which must be found to finish off this study!<\/p>\n

References<\/h2>\n
  1. F.S. Fawcett, and R.D. Lipscomb, \"CYANOGEN FLUORIDE\", Journal of the American Chemical Society<\/i>, vol. 82, pp. 1509-1510, 1960. https:\/\/doi.org\/10.1021\/ja01491a064<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    In 2010 I recounted the story of an organic chemistry tutorial, in which I asked the students the question “how would you synthesize 3-nitrobenzonitrile“. The expected answer was to generate a nitronium ion to nitrate benzonitrile, but can one invert this by generating a C\u2a78N+ ion to cyanate nitrobenzene? The students were then invited to […]<\/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":[1086],"tags":[],"ppma_author":[2661],"class_list":["post-23044","post","type-post","status-publish","format-standard","hentry","category-reaction-mechanism-2"],"yoast_head":"\nIs cyanogen chloride (fluoride) a source of C\u2a78N(+)? - 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=23044\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Is cyanogen chloride (fluoride) a source of C\u2a78N(+)? - Henry Rzepa's Blog\" \/>\n<meta property=\"og:description\" content=\"In 2010 I recounted the story of an organic chemistry tutorial, in which I asked the students the question “how would you synthesize 3-nitrobenzonitrile“. The expected answer was to generate a nitronium ion to nitrate benzonitrile, but can one invert this by generating a C\u2a78N+ ion to cyanate nitrobenzene? The students were then invited to […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044\" \/>\n<meta property=\"og:site_name\" content=\"Henry Rzepa's Blog\" \/>\n<meta property=\"article:published_time\" content=\"2020-11-28T08:23:52+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2020-12-02T09:55:34+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/12\/CN+.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":"Is cyanogen chloride (fluoride) a source of C\u2a78N(+)? - 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=23044","og_locale":"en_GB","og_type":"article","og_title":"Is cyanogen chloride (fluoride) a source of C\u2a78N(+)? - Henry Rzepa's Blog","og_description":"In 2010 I recounted the story of an organic chemistry tutorial, in which I asked the students the question “how would you synthesize 3-nitrobenzonitrile“. The expected answer was to generate a nitronium ion to nitrate benzonitrile, but can one invert this by generating a C\u2a78N+ ion to cyanate nitrobenzene? The students were then invited to […]","og_url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044","og_site_name":"Henry Rzepa's Blog","article_published_time":"2020-11-28T08:23:52+00:00","article_modified_time":"2020-12-02T09:55:34+00:00","og_image":[{"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/12\/CN+.jpg","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=23044#article","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044"},"author":{"name":"Henry Rzepa","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"headline":"Is cyanogen chloride (fluoride) a source of C\u2a78N(+)?","datePublished":"2020-11-28T08:23:52+00:00","dateModified":"2020-12-02T09:55:34+00:00","mainEntityOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044"},"wordCount":365,"commentCount":6,"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044#primaryimage"},"thumbnailUrl":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/12\/CN+.jpg","articleSection":["reaction mechanism"],"inLanguage":"en-GB","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044","name":"Is cyanogen chloride (fluoride) a source of C\u2a78N(+)? - Henry Rzepa's Blog","isPartOf":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044#primaryimage"},"image":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044#primaryimage"},"thumbnailUrl":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/12\/CN+.jpg","datePublished":"2020-11-28T08:23:52+00:00","dateModified":"2020-12-02T09:55:34+00:00","author":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281"},"breadcrumb":{"@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044#breadcrumb"},"inLanguage":"en-GB","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044"]}]},{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044#primaryimage","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/12\/CN+.jpg","contentUrl":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2010\/12\/CN+.jpg"},{"@type":"BreadcrumbList","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23044#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog"},{"@type":"ListItem","position":2,"name":"Is cyanogen chloride (fluoride) a source of C\u2a78N(+)?"}]},{"@type":"WebSite","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#website","url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/","name":"Henry Rzepa's Blog","description":"Chemistry with a twist","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-GB"},{"@type":"Person","@id":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/#\/schema\/person\/2b40f7b9c872a4dc1547e040a11b6281","name":"Henry Rzepa","image":{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g370be3a7397865e4fd161aefeb0a5a85","url":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/897b6740f7f599bca7942cdf7d7914af5988937ae0e3869ab09aebb87f26a731?s=96&d=blank&r=g","caption":"Henry Rzepa"},"description":"Henry Rzepa is Emeritus Professor of Computational Chemistry at Imperial College London.","sameAs":["https:\/\/orcid.org\/0000-0002-8635-8390"],"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?author=1"}]}},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/pDef7-5ZG","jetpack-related-posts":[{"id":14902,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=14902","url_meta":{"origin":23044,"position":0},"title":"A tutorial problem in stereoelectronic control. The Tiffeneau-Demjanov rearrangement as part of a prostaglandin synthesis.","author":"Henry Rzepa","date":"November 23, 2015","format":false,"excerpt":"This reaction emerged a few years ago (thanks Alan!) as a tutorial problem in organic chemistry, in which students had to devise a mechanism for the reaction and use this to predict the stereochemical outcome at the two chiral centres indicated with *. \u00a0It originates in a brief report from\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":"Click for 3D","src":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2015\/11\/green.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":20933,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=20933","url_meta":{"origin":23044,"position":1},"title":"Startling bonds: revisiting C\u2a78N+, via the helium bond in N\u2261C-He+.","author":"Henry Rzepa","date":"May 27, 2019","format":false,"excerpt":"Although the small diatomic molecule known as dicarbon or C2 has been known for a long time, its properties and reactivity have really only been determined\u00a0via its very high temperature generation. My interest started in 2010, when I speculatively proposed here that the related isoelectronic species C\u2a78N+ might sustain a\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":9706,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=9706","url_meta":{"origin":23044,"position":2},"title":"Kinetic vs Thermodynamic control. Subversive thoughts for electrophilic substitution of Indole.","author":"Henry Rzepa","date":"March 10, 2013","format":false,"excerpt":"I mentioned in the last post that one can try to predict the outcome of electrophilic aromatic substitution by approximating the properties of the transition state from those of either the reactant or the (presumed Wheland) intermediate by invoking Hammond's postulate. A third option is readily available nowadays; calculate the\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":"Click for 3D.","src":"https:\/\/i0.wp.com\/www.ch.imperial.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2013\/03\/3-NO-indole-ESP.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":23686,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23686","url_meta":{"origin":23044,"position":3},"title":"A reality-based suggestion for a molecule with a metal M\u2a78N quadruple bond.","author":"Henry Rzepa","date":"May 13, 2021","format":false,"excerpt":"I noted in an earlier post the hypothesized example of (CO)3Fe\u2a78C as exhibiting a carbon to iron quadruple bond and which might have precedent in known five-coordinate metal complexes where one of the ligands is a \"carbide\" or C ligand. I had previously mooted that the Fe\u2a78C combination might be\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\/2021\/05\/Screenshot-703-1024x818.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":23062,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=23062","url_meta":{"origin":23044,"position":4},"title":"Is cyanogen chloride (fluoride) a source of C\u2a78N(+)? More mechanistic insights.","author":"Henry Rzepa","date":"December 4, 2020","format":false,"excerpt":"I asked the question in my previous post. A computational mechanism revealed that AlCl3 or its dimer Al2Cl6 could catalyse a concerted 1,1-substitution reaction at the carbon of Cl-C\u2261N, with benzene displacing chloride which is in turn captured by the Al. Unfortunately the calculated barrier for this simple process was\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":"https:\/\/i0.wp.com\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2020\/12\/CNAl-1024x889.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":16031,"url":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=16031","url_meta":{"origin":23044,"position":5},"title":"Ways to encourage water to protonate an amine: superbasing.","author":"Henry Rzepa","date":"April 8, 2016","format":false,"excerpt":"Previously, I looked at\u00a0models of how\u00a0ammonia could be protonated by water to form ammonium hydroxide. The energetic outcome of my\u00a0model matched the known equilbrium in water as favouring the unprotonated form (pKb ~4.75). I add here two amines for which\u00a0R=Me3Si and R=CN. The idea is that the first will assist\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":[]}],"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\/23044","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=23044"}],"version-history":[{"count":13,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/23044\/revisions"}],"predecessor-version":[{"id":23065,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=\/wp\/v2\/posts\/23044\/revisions\/23065"}],"wp:attachment":[{"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=23044"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=23044"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=23044"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fppma_author&post=23044"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}