{"id":7348,"date":"2013-05-29T16:14:19","date_gmt":"2013-05-29T21:14:19","guid":{"rendered":"https:\/\/www.masterorganicchemistry.com\/?p=7348"},"modified":"2026-05-06T19:06:59","modified_gmt":"2026-05-07T00:06:59","slug":"alkyne-halogenation-bromination-chlorination","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2013\/05\/29\/alkyne-halogenation-bromination-chlorination\/","title":{"rendered":"Alkyne Halogenation: Bromination and Chlorination of Alkynes"},"content":{"rendered":"<p><strong><strong>Halogenation of Alkynes With Br<sub>2<\/sub> and Cl<sub>2<\/sub><\/strong><\/strong><\/p>\n<ul>\n<li>Like alkenes, alkynes can undergo <strong>halogenation<\/strong> with Cl<sub>2<\/sub>, and Br<sub>2\u00a0<\/sub><\/li>\n<li>When 1 equivalent of the halogen is used, the products of these reactions are <em>trans<\/em>-dihaloalkenes.<\/li>\n<li>Like halogenation of alkenes, the reaction is believed to proceed through a bridged intermediate<\/li>\n<li>Alkynes react more slowly than alkenes towards Br<sub>2<\/sub> and Cl<sub>2\u00a0<\/sub> by 3-5 orders of magnitude<\/li>\n<li>Addition of a second equivalent of a halogen gives tetrahaloalkanes.<\/li>\n<\/ul>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-41483\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/0-summary-halogenation-of-alkynes-with-halogens-cl2-br2-gives-mostly-trans-dihaloalkenes.gif\" alt=\"-summary-halogenation of alkynes with halogens cl2 br2 gives mostly trans dihaloalkenes\" width=\"800\" height=\"596\" \/><\/a><\/p>\n<p><strong>Table of Contents<\/strong><\/p>\n<ol>\n<li style=\"list-style-type: none;\">\n<ol>\n<li><a href=\"#one\">Halogenation of Alkynes With Cl2 and Br2<\/a><\/li>\n<li><a href=\"#two\">Halogenation of Alkynes Also Proceeds Through a Bridged Ion INtermediate, Providing\u00a0<em>trans<\/em> Products<\/a><\/li>\n<li><a href=\"#three\">Addition Of A Second Equivalent of Halogen Gives Tetrahalogenated Products<\/a><\/li>\n<li><a href=\"#notes\">Notes<\/a><\/li>\n<li><a href=\"#quiz\">Quiz Yourself!<\/a><\/li>\n<li><a href=\"#references\">(Advanced) References and Further Reading<\/a><\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<hr \/>\n<h2><a id=\"one\"><\/a>1. Halogenation of Alkynes With Cl<sub>2 <\/sub>and Br<sub>2<\/sub><\/h2>\n<p>If you&#8217;ll recall from the series of posts on alkenes, alkenes react with certain electrophiles (such as halogens, among others) to give <strong>positively charged bridged intermediates. <\/strong>(<span style=\"color: #800080;\"><a style=\"color: #800080;\" href=\"https:\/\/www.masterorganicchemistry.com\/2013\/03\/15\/alkene-bromination-mechanism\/\"><em>See article &#8211; Bromination of Alkenes<\/em><\/a><\/span>). \u00a0Common examples are the &#8220;bromonium ion&#8221; and the &#8220;mercurinium ion&#8221;.\u00a0 These intermediates then undergo backside attack by a nucleophile, resulting in overall <em>anti<\/em> addition across the double bond (<span style=\"color: #800080;\"><a style=\"color: #800080;\" href=\"https:\/\/www.masterorganicchemistry.com\/2013\/01\/22\/alkene-addition-regioselectivity-syn-anti\/\"><em>See article &#8211; Syn and Anti<\/em><\/a><\/span>) .<\/p>\n<p>How do the addition of Br<sub>2<\/sub> and Cl<sub>2<\/sub> across <strong>alkynes<\/strong> compare to their reactions with\u00a0 alkenes with these reagents?<\/p>\n<p>We might expect that alkynes, being so similar to alkenes, should also react in a similar fashion. Then again, this is organic chemistry, and sometimes changing one seemingly small variable can give an extremely different result (<span style=\"color: #800080;\">should you have any doubt on this, see <em><a style=\"color: #800080;\" href=\"https:\/\/www.masterorganicchemistry.com\/2024\/01\/23\/alkyne-hydroboration-with-r2bh\/\">Hydroboration of Alkynes<\/a><\/em>)\u00a0<\/span><\/p>\n<p>Happily for us,<strong> the reaction of alkynes with electrophiles such as Cl<sub>2 <\/sub>and\u00a0Br<sub>2 <\/sub><em>does<\/em> give very similar results to what is observed with alkenes.<\/strong><\/p>\n<p>For example, treatment of an alkyne with 1 equivalent of Br<sub>2<\/sub> provides a dibrominated alkene with the two bromides opposite to each other, to give us <em>trans<\/em>-dihalides. [<span style=\"color: #993366;\"><em>For slightly more detail, see<\/em><\/span> <a href=\"#one\">Note 1<\/a>.]<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-41372\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/1-Bromination-of-alkynes-with-br2-gives-trans-dibromoalkenes-with-best-selectivity-for-aliphatic-alkynes.gif\" alt=\"Bromination of alkynes with br2 gives trans dibromoalkenes with best selectivity for aliphatic alkynes\" width=\"640\" height=\"477\" \/><\/a><\/p>\n<p>The story is similar with Cl<sub>2<\/sub>. Products of trans addition dominate. Although for more detail, see <a href=\"#notetwo\">Note 2<\/a>.<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-41373\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/2-chlorination-of-alkynes-with-cl2-gives-mostly-trans-dichloroalkenes-but-diminished-selectivity-and-lower-yields.gif\" alt=\"chlorination of alkynes with cl2 gives mostly trans dichloroalkenes but diminished selectivity and lower yields\" width=\"640\" height=\"237\" \/><\/a><\/p>\n<h2><a id=\"two\"><\/a>2. Halogenation of Alkynes Also Proceeds Through A Bridged-Ion Intermediate, Providing <em>Trans<\/em> Products<\/h2>\n<p>So how does this reaction work?<\/p>\n<p>Given that the reaction predominantly gives\u00a0<em>trans<\/em> dihalides, the prevailing view of the mechanism is that it passes through a bridged halonium ion intermediate similar to that observed for alkenes.<\/p>\n<p>In the first step, a pi-bond from the alkyne acts as a nucleophile, attacking Br<sub>2<\/sub> and giving rise to a bridged-ion intermediate.<\/p>\n<p>In the next step, a halide\u00a0ion attacks the carbon from the back face, leading to the <em>trans<\/em> product.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-41374\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/3-mechanism-for-bromination-of-alkynes-involves-formation-of-cyclic-bromonium-ion-followed-by-attack-to-give-trans-dibromoalkenes.gif\" alt=\"mechanism for bromination of alkynes involves formation of cyclic bromonium ion followed by attack to give trans dibromoalkenes\" width=\"640\" height=\"364\" \/><\/a><\/p>\n<p>There is actually a\u00a0<em>very<\/em> interesting observation to point out here, but I&#8217;ll leave that to the &#8220;Notes&#8221; section below as it is not absolutely essential for most readers&#8217; purposes. Here&#8217;s the teaser, though: alkynes are considerably <em>slower<\/em> to react than alkenes are. [<a href=\"#notetwo\">Note 3<\/a>].<\/p>\n<h2><a id=\"three\"><\/a>3. Addition of a Second Equivalent of Halogen Results in Tetrasubstituted Products<\/h2>\n<p>Once the dihalogenated alkene is formed, it&#8217;s possible to subject that alkene to a\u00a0<strong>second\u00a0<\/strong>halogenation, leading to the formation of a\u00a0<strong>tetrahalogenated\u00a0<\/strong>alkane.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-41375\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/4-addition-of-a-second-equivalent-of-halogen-to-the-dihaloalkene-gives-tetrahaloalkanes.gif\" alt=\"addition of a second equivalent of halogen to the dihaloalkene gives tetrahaloalkanes\" width=\"640\" height=\"281\" \/><\/a><\/p>\n<p>This can either be the same halogen (Br<sub>2<\/sub>) or a different one (Cl<sub>2<\/sub>) depending on your needs.<\/p>\n<hr \/>\n<h2><strong><a id=\"notes\"><\/a>Notes<\/strong><\/h2>\n<div class=\"related-articles\"><p><strong>Related Articles<\/strong><\/p><ul><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/06\/04\/oxidation-of-alkynes\/\" class=\"\"><span>Oxidation of Alkynes With O3 and KMnO4<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/06\/24\/alkynes-are-a-blank-canvas\/\" class=\"\"><span>Alkynes Are A Blank Canvas<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2014\/01\/29\/synthesis-5-reactions-of-alkynes\/\" class=\"\"><span>Synthesis (5) \u2013 Reactions of Alkynes<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2022\/06\/21\/keto-enol-tautomerism-key-points\/\" class=\"\"><span>Keto-Enol Tautomerism<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/03\/20\/alkene-addition-pattern-2-the-three-membered-ring-pathway\/\" class=\"\"><span>Alkene Addition Pattern #2: The \u201cThree-Membered Ring\u201d Pathway<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/03\/15\/alkene-bromination-mechanism\/\" class=\"\"><span>Bromination of Alkenes: The Mechanism<\/span><\/a><\/li><\/ul><\/div>\n<p><strong><a id=\"noteone\"><\/a>Note 1<\/strong>. This falls firmly into the &#8220;You Don&#8217;t Need To Know This For Org 1 \/ Org 2&#8221; category, so here goes. While aliphatic alkynes (i.e. alkynes attached to alkyl groups) tend to give only\u00a0<em>trans\u00a0<\/em>dibromides, with aryl alkynes there is considerably less selectivity for the\u00a0<em>trans<\/em> product. For instance, in the example above, we saw that phenylacetylene only gave a 82:18 ratio of <em>trans<\/em>: <em>cis<\/em> whereas there were no <em>cis<\/em> products observed at all for 3-hexyne.<\/p>\n<p>This loss of stereoselectivity likely reflects a slightly different mechanism may be in play. One mechanism that has been proposed is the intermediacy of a vinyl cation, which could undergo attack from either face.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-41376\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F1-mechanism-of-bromination-of-phenylacetylene-through-vinyl-cation-intermediate-gives-reduced-selectivity-for-trans-dibromides.gif\" alt=\"mechanism of bromination of phenylacetylene through vinyl cation intermediate gives reduced selectivity for trans dibromides\" width=\"640\" height=\"335\" \/><\/a><\/p>\n<p><strong><a id=\"notetwo\"><\/a>Note 2.<\/strong> Also falls into &#8220;You Don&#8217;t Really Need To Know This&#8221;, but chlorination is a considerably worse reaction than bromination (less selective).<br \/>\nFor the reaction of Cl<sub>2<\/sub> with 3-hexyne and 2-butyne, <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo01300a024\">Yates and Go<\/a> note, &#8220;<em>these reactions are not clean, and many products were found&#8221;<\/em>.\u00a0 For the chlorination of 3-hexyne shown in the scheme above, the actual yield of <em>trans-<\/em>dichlroalkene was 19% and the yield of\u00a0<em>cis<\/em>-dichloroalkene was 7%. The major product (51%) incorporated acetic acid into the final product via\u00a0<em>trans<\/em><em>\u00a0<\/em>addition. This shows that a cyclic bridged ion intermediate is likely still present. ( Interestingly, the reactions of terminal alkynes (1-hexyne and 1-pentyne) cleanly gives only <em>syn<\/em> addition products, which the authors speculate proceeds via a vinyl cation followed by quick trapping of the proximal chloride ion.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-41377\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F2-chlorination-of-alkyl-acetylenes-has-poor-yields-of-trans-dichloroalkenes-and-lots-of-incorporation-of-acetic-acid.gif\" alt=\"chlorination of alkyl acetylenes has poor yields of trans dichloroalkenes and lots of incorporation of acetic acid\" width=\"640\" height=\"224\" \/><\/a><\/p>\n<p><strong><a id=\"notethree\"><\/a>Note 3.\u00a0 <\/strong>Since the reaction goes through essentially the same pathway for alkenes as for alkynes, it presents us with an opportunity for an interesting experiment.<\/p>\n<p>What reacts faster, alkenes or alkynes?<\/p>\n<p>Researchers addressed this question by treating alkenes and alkynes with very similar structures (e.g.\u00a0<em>trans<\/em>-3-hexene vs. 3-hexyne) and measuring the rate constants.<\/p>\n<p>It was found that\u00a0<strong>alkenes\u00a0<\/strong>react with Cl<sub>2<\/sub> and Br<sub>2<\/sub>\u00a0 <strong>considerably faster <\/strong>than alkynes of similar structure, by factors of 1000 up to 100,000.<\/p>\n<p>Another way of saying this is that the pi-bonds of alkenes are better nucleophiles than alkynes.<\/p>\n<p>Remember that <em>sp<\/em>-hybridized carbons are <strong>better<\/strong> at <strong>stabilizing<\/strong> <strong>negative<\/strong> <strong>charge<\/strong> since the orbitals are <strong>closer<\/strong> to the nucleus? Well, that same effect means that these carbons are\u00a0<strong>poorer\u00a0<\/strong>at stabilizing\u00a0<strong>positive charge\u00a0<\/strong>(i.e. a lack of electron density) since, in effect, you are bringing an electron-deficient orbital closer to the nucleus.<\/p>\n<p>You can think of alkynes as holding on to their electrons slightly more tightly than do alkenes.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-41378\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F3-acetylenes-are-not-as-reactive-as-alkenes-with-halogenation-rates-of-bromination-are-several-orders-of-magnitude-faster-with-alkenes-olefins.gif\" alt=\"acetylenes are not as reactive as alkenes with halogenation - rates of bromination are several orders of magnitude faster with alkenes olefins\" width=\"640\" height=\"348\" \/><\/a><\/p>\n<p>Furthermore, the additional double bond leads to considerably more <em>ring strain<\/em>;<em> sp<sup>2<\/sup><\/em> hybridized carbons [ideal angle 120\u00b0] constrained into a triangle [internal angle 60\u00b0] is more unstable than an <em>sp<sup>3<\/sup><\/em> hybridized carbon [ideal angle 109\u00b0] would be.<\/p>\n<p>There&#8217;s a second point which doesn&#8217;t become apparent for most students until second-semester organic chemistry. The 3-membered ring intermediate formed has <em>antiaromatic <\/em>character. (<em>See post: <a href=\"https:\/\/www.masterorganicchemistry.com\/2017\/03\/27\/antiaromaticity\/\">Antiaromaticity<\/a><\/em>)<\/p>\n<p>&nbsp;<\/p>\n<hr \/>\n<h2><strong><a id=\"quiz\"><\/a>Quiz Yourself!<\/strong><\/h2>\n\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3585-Front-Image-Only.png\" alt=\"\" width=\"640\" height=\"616\" \/><\/p>\n<p><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a\u00a0 MOC member<\/strong><\/a> to see the clickable quiz with answers on the back. <br \/>\n<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-36214 aligncenter\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/0717-Front-Image-Only.png\" alt=\"\" width=\"600\" height=\"450\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a MOC member<\/strong><\/a> to see the clickable quiz with answers on the back.<\/p>\n<p><br \/>\n<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-36214 aligncenter\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/0718-Front-Image-Only.png\" alt=\"\" width=\"600\" height=\"450\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a MOC member<\/strong><\/a> to see the clickable quiz with answers on the back.<\/p>\n<p><br \/>\n<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-36214 aligncenter\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/0720-Front-Image-Only.png\" alt=\"\" width=\"600\" height=\"450\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a MOC member<\/strong><\/a> to see the clickable quiz with answers on the back.<\/p>\n<p><\/p>\n<hr \/>\n<h2><strong><a id=\"references\"><\/a>(Advanced) References and Further Reading<\/strong><\/h2>\n<p>Good reviews are to be found in Carey and Sundberg A.\u00a0 Chapter 6 (Polar Addition and Elimination Reactions) p. 374 in the 4th ed. Also, Patai&#8217;s Chemistry of Triple Bonded Functional Groups part 1, p. 539 has a good discussion of the mechanism (vinyl cations with phenyl substituents, bridged intermediates with alkyl acetylenes).<\/p>\n<ol>\n<li><strong>Untersuchungen \u00fcber Alloisomerie. II<br \/>\n<\/strong>Arthur Michael<strong><br \/>\n<\/strong><em>J. Prakt. Chem.<\/em><strong> 1892, <\/strong>46 (1), 209-210<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1002\/prac.18920460115\">10.1002\/prac.18920460115<\/a><br \/>\nAn early paper on the bromination of alkynes. This paper mentions that bromination of dicarboxyacetylene gave 70% of the <em>trans<\/em> isomer!<\/li>\n<li><strong>Kinetics and mechanism of electrophilic bromination of acetylenes<br \/>\n<\/strong>James A. Pincock, Keith Yates<strong><br \/>\n<\/strong><em>Canadian Journal of Chemistry<\/em><strong>, 1970<\/strong>, <em>48<\/em> (21): 3332-3348<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/www.nrcresearchpress.com\/doi\/10.1139\/v70-561#.X2D5WxNKh24\">1139\/v70-561<\/a><br \/>\nStereoselective <em>anti<\/em> addition was found in the bromination of 3-hexyne, but both <em>cis<\/em> and <em>trans<\/em> products were obtained in the bromination of phenylacetylene. Notably, the reaction was found to be about 10<sup>5<\/sup> faster for 3-hexene than for 3-hexyne in acetic acid.<\/li>\n<li><strong>Vinyl cation intermediates in electrophilic additions to triple bonds. 2. Chlorination of alkylacetylenes<\/strong><br \/>\nKeith Yates and T. Andrew Go<br \/>\n<em>The Journal of Organic Chemistry<\/em> <strong>1980<\/strong> 45 (12), 2385-2391<br \/>\n<strong>DOI:<\/strong> <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo01300a024\">10.1021\/jo01300a024<\/a><br \/>\nElectrophilic chlorination of alkyl acetylenes is less stereospecific than for bromination. Yields are lower, and there is more incorporation of solvent.<\/li>\n<li><strong>The Stereochemistry of Electrophilic Additions to Olefins and Acetylenes<br \/>\n<\/strong>Robert C. Fahey<strong><br \/>\n<\/strong><em>Topics in Stereochemistry<\/em><strong> 1968<\/strong>, <em>3<\/em>, 237-342<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/abs\/10.1002\/9780470147122.ch4\">1002\/9780470147122.ch4<\/a><br \/>\nThis review is more weighted towards alkene reactions, but does contain sections on the addition of Cl<sub>2<\/sub> and Br<sub>2<\/sub> to acetylenes. On pg. 291, the author states, \u201c[\u2026] <em>bromine additions to acetylenes<\/em> [\u2026] <em>in acetic acid follow kinetics similar to those found for olefins, but that acetylenes are 100- to 50,000-fold less reactive than the corresponding olefins<\/em>\u201d.<\/li>\n<li><strong>Electron transmission study of the splitting of the <\/strong><strong>p<\/strong><strong>* molecular orbitals of angle-strained cyclic acetylenes: implications for the electrophilicity of alkynes<br \/>\n<\/strong>Lily Ng, Kenneth D. Jordan, Adolf Krebs, and Wolfgang Rueger<strong><br \/>\n<\/strong><em>Journal of the American Chemical Society<\/em><strong> 1982<\/strong>, <em>104<\/em> (26), 7414-7416<strong><br \/>\nDOI: <\/strong><a href=\"https:\/\/pubs.acs.org\/doi\/abs\/10.1021\/ja00390a005\">1021\/ja00390a005<\/a><br \/>\nAnother possible explanation for the lower reactivity of alkynes relative to alkenes has to do with the availability of the unfilled orbital in the alkyne. It has been shown that a p* orbital of bent alkynes (e.g. cyclooctyne) has a lower energy than the p* orbital of alkenes, and it has been suggested that linear alkynes can achieve a bent structure in their transition states when reacting with an electrophile.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>Halogenation of Alkynes With Br2 and Cl2 Like alkenes, alkynes can undergo halogenation with Cl2, and Br2\u00a0 When 1 equivalent of the halogen is used, <\/p>\n","protected":false},"author":1,"featured_media":41483,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1419],"tags":[477,929,185,310,928,382,233,476],"post_folder":[],"class_list":["post-7348","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-alkyne-reactions","tag-alkynes-2","tag-antiaromatic","tag-bromine","tag-chlorination","tag-chlorine","tag-halogenation","tag-mechanisms-2","tag-trans"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Halogenation of Alkynes: Bromination, Chlorination &amp; Iodination of Alkynes<\/title>\n<meta name=\"description\" content=\"Reaction of alkynes with electrophiles such as Cl2, Br2, and I2 provides very similar results to what is observed with alkenes; trans-dihalogenated alkenes\" \/>\n<meta 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