{"id":26523,"date":"2023-10-12T12:57:24","date_gmt":"2023-10-12T11:57:24","guid":{"rendered":"https:\/\/www.ch.imperial.ac.uk\/rzepa\/blog\/?p=26523"},"modified":"2023-10-12T13:03:31","modified_gmt":"2023-10-12T12:03:31","slug":"more-examples-of-double-headed-curly-arrows-s-and-c-nucleophiles-attacking-acetyl-chloride","status":"publish","type":"post","link":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=26523","title":{"rendered":"More examples of &#8220;double-headed&#8221; curly arrows: S and C Nucleophiles attacking acetyl chloride"},"content":{"rendered":"<div class=\"kcite-section\" kcite-section-id=\"26523\">\n<p>In an earlier post on this topic,<span id=\"cite_ITEM-26523-0\" name=\"citation\"><a href=\"#ITEM-26523-0\">[1]<\/a><\/span><sup>\u2021<\/sup> I described how the curly-arrows describing the mechanism of a nucleophilic addition at a carbonyl group choreograph in two distinct ways, as seen in red or blue below. The arrows in red can be described as firstly addition to the carbonyl group to form either a transient intermediate (a two-step process) or instead a formal transition state state as a concerted single-step mechanism. The blue arrows do the reverse; firstly elimination and then followed by addition. I will use the shorthand <strong>AE<\/strong> for the first type and <strong>EA<\/strong> for the second type. Here I explore some more nucleophiles to see which of these two mechanisms they follow. Data for these results can be found at <a href=\"https:\/\/doi.org\/10.14469\/hpc\/13171\">10.14469\/hpc\/13171<\/a><br \/>\n<a href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/double-headed4.svg\"><img decoding=\"async\" class=\"aligncenter size-full wp-image-26546\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/double-headed4.svg\" alt=\"\" width=\"450\" \/><\/a><strong>N- carbon ylid:<\/strong> This is a very facile (low-barrier) reaction with a C-O bond length response that initially increases steeply, followed by a more modest decline and hence corresponds to an <strong>AE<\/strong> mechanism.<\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26534\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chlorine-C-Nuc_tot_ener.gif\" alt=\"\" width=\"540\" \/><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26530\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chlorine-C-Nuc_tot_ener.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26535\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chlorine-add-C-nuc-DM.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26536\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chlorine-C-Nuc-BL.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p><strong>P carbon-Ylid:<\/strong>\u00a0 Essentially identical to the previous example, and again an <strong>AE<\/strong> mechanism.<\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26527\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-P-ylid.gif\" alt=\"\" width=\"540\" \/><\/p>\n<p><a href=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-P-ylid_tot_ener.svg\"><img decoding=\"async\" class=\"aligncenter size-full wp-image-26524\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-P-ylid_tot_ener.svg\" alt=\"\" width=\"450\" \/><\/a><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26525\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-P-ylid_DM.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26526\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-P-ylid_BL12.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p><strong>S carbon-ylid: <\/strong>Again, an AE mechanism.<\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26533\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-S-ylid.gif\" alt=\"\" width=\"540\" \/><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26529\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-S-ylid_tot_ener.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26531\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-S-ylid_DM.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26532\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-S-ylid_BL12.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p><strong>S-nucleophile:\u00a0<\/strong> This one is different, showing a larger barrier and initial small decrease in the C-O length followed by a larger increase. This one is an <strong>EA<\/strong> mechanism.<\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26537\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-MeSH_tot_ener.gif\" alt=\"\" width=\"540\" \/><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26528\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-MeSH_tot_ener.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26538\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-MeSH_DM.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p><img decoding=\"async\" class=\"aligncenter size-medium wp-image-26539\" src=\"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/wp-content\/uploads\/2023\/10\/acetyl-chloride-MeSH_BL12.svg\" alt=\"\" width=\"450\" \/><\/p>\n<p>As I noted previously, it would be useful to have two double headed curly arrows available in palletes of these; <strong style=\"color: red;\">&lt;\u2014&gt;<\/strong> (AE) and <strong style=\"color: blue;\">&gt;\u2014&lt;<\/strong> (EA) to illustrate the difference between the two mechanistic types.<\/p>\n<hr \/>\n<p><sup>\u2021<\/sup>This is the first instance where I cite a blog using a CrossRef DOI generated for it. Previous such citations used a DataCite DOI, which the bibliographic software used here to add them to the post (Kcite) does not support.<\/p>\n<hr \/>\n<h2>References<\/h2>\n    <ol class=\"kcite-bibliography csl-bib-body\"><li id=\"ITEM-26523-0\">H. Rzepa, \"The &quot;double-headed&quot; curly arrow as used in mechanistic representations.\", 2023. <a href=\"https:\/\/doi.org\/10.59350\/f00wf-5tq46\">https:\/\/doi.org\/10.59350\/f00wf-5tq46<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> <!-- kcite-section 26523 -->","protected":false},"excerpt":{"rendered":"<p>In an earlier post on this topic,\u2021 I described how the curly-arrows describing the mechanism of a nucleophilic addition at a carbonyl group choreograph in two distinct ways, as seen in red or blue below. The arrows in red can be described as firstly addition to the carbonyl group to form either a transient intermediate [&hellip;]<\/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":[],"tags":[2648],"ppma_author":[2661],"class_list":["post-26523","post","type-post","status-publish","format-standard","hentry","tag-interesting-chemistry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.4 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>More examples of &quot;double-headed&quot; curly arrows: S and C Nucleophiles attacking acetyl chloride - Henry Rzepa&#039;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=26523\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"More examples of &quot;double-headed&quot; curly arrows: S and C Nucleophiles attacking acetyl chloride - Henry Rzepa&#039;s Blog\" \/>\n<meta property=\"og:description\" content=\"In an earlier post on this topic,\u2021 I described how the curly-arrows describing the mechanism of a nucleophilic addition at a carbonyl group choreograph in two distinct ways, as seen in red or blue below. 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