{"id":7371,"date":"2013-06-04T16:29:13","date_gmt":"2013-06-04T21:29:13","guid":{"rendered":"https:\/\/www.masterorganicchemistry.com\/?p=7371"},"modified":"2025-07-08T15:03:04","modified_gmt":"2025-07-08T20:03:04","slug":"oxidation-of-alkynes","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2013\/06\/04\/oxidation-of-alkynes\/","title":{"rendered":"Oxidation of Alkynes With O3 and KMnO4"},"content":{"rendered":"<p><strong>Oxidation of Alkynes with Ozone and KMnO<sub>4<\/sub><\/strong><\/p>\n<ul>\n<li>As we&#8217;ve seen previously, alkenes (olefins) can be oxidized to carbonyl compounds (aldehydes, ketones, carboxylic acids) with ozone and KMnO<sub>4<\/sub>.<span style=\"color: #800080;\"> <em>(See article &#8211; <a style=\"color: #800080;\" href=\"https:\/\/www.masterorganicchemistry.com\/2013\/04\/23\/alkene-reactions-ozonolysis\/\">Alkene Reactions &#8211; Ozonolysis<\/a>)\u00a0<\/em><\/span><\/li>\n<li>Alkynes can also undergo oxidative cleavage with ozone and KMnO4.<\/li>\n<li>The products depend both on the structure of the alkyne and the reaction conditions.<\/li>\n<li>With internal alkynes R-C\u2261C-R , ozonolysis (or KMnO4) gives two <strong>carboxylic acids<\/strong>, R-CO2H.<\/li>\n<li>With\u00a0<strong>terminal\u00a0<\/strong>alkynes,\u00a0R-C\u2261C-H, ozonolysis produces a single equivalent of carbon dioxide (CO2) and a chain-shortened carboxylic acid.<\/li>\n<li>Additionally, reaction conditions can be modified such that C-C bond cleavage does not occur and 1,2-diketones are formed.<\/li>\n<\/ul>\n<p>Two oxidation reactions of alkenes that do <em>not<\/em> translate well to alkynes are the reaction of alkynes with OsO<sub>4<\/sub> (dihydroxylation) and epoxidation with peroxyacids (e.g. <em>m<\/em>-CPBA). While alkynes <em>do<\/em> react with these reagents, the reaction products are complex, and we will not dwell on them except perhaps to gawk at the results in the footnotes at the bottom of this article.<\/p>\n<p>[summary image]<\/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\">Oxidative Cleavage of Alkynes via Ozonolysis (O<sub>3<\/sub>)<\/a><\/li>\n<li><a href=\"#two\">Oxidative Cleavage of Alkynes with KMnO<sub>4<\/sub><\/a><\/li>\n<li><a href=\"#three\">Formation of 1,2-Diketones From Alkynes<\/a><\/li>\n<li><a href=\"#notes\">Notes<\/a><\/li>\n<li><a href=\"#quizzes\">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. Oxidative Cleavage of Alkynes via Ozonolysis<\/h2>\n<ul>\n<li>We&#8217;ve seen that alkenes (olefins) can be oxidized to carbonyl compounds (aldehydes, ketones, carboxylic acids) with ozone and KMnO<sub>4<\/sub>.<span style=\"color: #800080;\"> <em>(See article &#8211; <a style=\"color: #800080;\" href=\"https:\/\/www.masterorganicchemistry.com\/2013\/04\/23\/alkene-reactions-ozonolysis\/\">Alkene Reactions &#8211; Ozonolysis<\/a>)\u00a0<\/em><\/span><\/li>\n<\/ul>\n<p>The next logical question is: what about <strong>alkynes<\/strong>? Can we cleave them too? Not that you&#8217;d really <em>want<\/em> to in most circumstances, saying as alkynes are a wonderful <a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/06\/24\/alkynes-are-a-blank-canvas\/\">blank canvas <\/a>\u00a0for organic synthesis and can be turned into a huge array of useful functional groups&#8230;. but if you <strong>had<\/strong> to, could you?<\/p>\n<p>It turns out that the answer is yes!<\/p>\n<p>The products that are obtained depends on the structure of the alkyne and the reaction conditions.<\/p>\n<p>Internal alkynes, R-C\u2261C-R , can be cleaved via ozonolysis to give\u00a0<strong>carboxylic acids.\u00a0<\/strong>When the alkyne is symmetrical, this gives two identical carboxylic acids.<\/p>\n<p>A prime example is the ozonolysis of\u00a0<strong>diphenylacetylene<\/strong>, which gives benzoic acid.<\/p>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-41551\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/1-ozonolysis-of-alkynes-by-ozone-giving-carboxylic-acids-yields-are-fairly-low-intermediate-ozonide.gif\" alt=\"ozonolysis of alkynes by ozone giving carboxylic acids yields are fairly low intermediate ozonide\" width=\"640\" height=\"246\" \/><\/a><\/p>\n<p>Terminal alkynes, R-C\u2261C-H, also undergo oxidative cleavage. In this case, the terminal carbon bubbles out of the reaction mixture as carbon dioxide (CO<sub>2<\/sub>) and we are left with a chain-shortened carboxylic acid.<\/p>\n<p>For example, 1-hexyne becomes pentanoic acid plus carbon dioxide:<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-41552\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/2-ozonolysis-of-alkynes-by-ozone-giving-carboxylic-acids-yields-are-fairly-low-intermediate-ozonide-2.gif\" alt=\"ozonolysis of alkynes by ozone giving carboxylic acids yields are fairly low intermediate ozonide 2\" width=\"640\" height=\"378\" \/><\/a><\/p>\n<p>The original product of ozonolysis would be formic acid, HCO<sub>2<\/sub>H, but in the presence of ozone the C-H bond is oxidized further to give carbonic acid, CO(OH)<sub>2<\/sub> . Whether during ozonolysis or in a open can of Diet Coke, carbonic acid is in equilibrium with CO<sub>2<\/sub> and H<sub>2<\/sub>O, and gradually CO<sub>2<\/sub> is lost to the atmosphere.<\/p>\n<h2><a id=\"two\"><\/a>2. Cleavage of Alkynes With Permanganate (KMnO<sub>4<\/sub>)<\/h2>\n<p>Under certain conditions potassium permanganate can also cleave carbon-carbon triple bonds.<\/p>\n<p>For example, it is reported that KMnO<sub>4<\/sub> under either strongly basic or strongly acidic conditions will break apart internal alkynes to give carboxylic acids.<\/p>\n<p>As with ozonolysis, terminal alkynes are converted to the chain-shortened carboxylic acid and one equivalent of CO<sub>2<\/sub>.<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-41553\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/3-kmno4-potassium-permanganate-cleaves-alkynes-to-give-carboxylic-acids-terminal-alkynes-cleaved-to-give-co2.gif\" alt=\"kmno4 potassium permanganate cleaves alkynes to give carboxylic acids terminal alkynes cleaved to give co2\" width=\"640\" height=\"342\" \/><\/a><\/p>\n<h2><a id=\"three\"><\/a>3. Formation of 1,2-Diketones From Alkynes<\/h2>\n<p>As noted previously, forming carboxylic acids from alkynes, while occasionally useful, seems like a waste of two good C-C pi bonds that could otherwise be converted into something more interesting.<\/p>\n<p>Thus, I am happy to report to you that under certain condtions, C-C triple bonds can be directly converted into 1,2-diketones.<\/p>\n<p>Here, for example, is the reaction of phenylacetylene with KMnO<sub>4<\/sub> to give benzil.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-41554\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/4-alkynes-can-be-oxidized-to-diketones-with-O3-or-with-KMnO4-under-certain-conditions.gif\" alt=\"alkynes can be oxidized to diketones with O3 or with KMnO4 under certain conditions\" width=\"640\" height=\"230\" \/><\/a><\/p>\n<p>A number of other oxidants (e.g. RuO<sub>4<\/sub>) can also carry out this conversion, as does OsO<sub>4<\/sub>. [<a href=\"#noteone\">Note 1<\/a>]<\/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\/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\/2013\/05\/14\/hydroboration-and-oxymercuration-of-alkynes\/\" class=\"\"><span>Hydroboration and Oxymercuration of Alkynes<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/05\/01\/the-2-most-important-reactions-of-alkynes\/\" class=\"\"><span>Acetylides from Alkynes, And Substitution Reactions of Acetylides<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/05\/08\/lindlar-nanh3-partial-reduction-of-alkynes\/\" class=\"\"><span>Partial Reduction of Alkynes With Lindlar\u2019s Catalyst or Na\/NH3 To Obtain Cis or Trans Alkenes<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/05\/29\/alkyne-halogenation-bromination-chlorination\/\" class=\"\"><span>Alkyne Halogenation: Bromination, Chlorination, and Iodination of Alkynes<\/span><\/a><\/li><\/ul><\/div>\n<p>Some highlights from chapter 13 of Patai&#8217;s &#8220;Chemistry of Triple Bonded Functional Groups&#8221; Part 1, supplement C.<\/p>\n<p><strong><a id=\"noteone\"><\/a>Note 1.\u00a0<\/strong>On OsO<sub>4<\/sub>. Here&#8217;s what can happen if alkynes are treated with OsO<sub>4<\/sub>. They perform double addition (note that this is a proposed structure, not a conclusive proof) which can then be hydrolyzed to give a diketone.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-41555\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F1-osmium-tetraoxide-oxidation-of-acetylene-followed-by-oxidation-gives-diketones-from-patai.jpg\" alt=\"osmium tetraoxide oxidation of acetylene followed by oxidation gives diketones from patai\" width=\"640\" height=\"487\" srcset=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F1-osmium-tetraoxide-oxidation-of-acetylene-followed-by-oxidation-gives-diketones-from-patai.jpg 1400w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F1-osmium-tetraoxide-oxidation-of-acetylene-followed-by-oxidation-gives-diketones-from-patai-300x228.jpg 300w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F1-osmium-tetraoxide-oxidation-of-acetylene-followed-by-oxidation-gives-diketones-from-patai-1024x780.jpg 1024w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F1-osmium-tetraoxide-oxidation-of-acetylene-followed-by-oxidation-gives-diketones-from-patai-768x585.jpg 768w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F1-osmium-tetraoxide-oxidation-of-acetylene-followed-by-oxidation-gives-diketones-from-patai-760x579.jpg 760w\" sizes=\"(max-width: 640px) 100vw, 640px\" \/><\/a><\/p>\n<p><strong><a id=\"notetwo\"><\/a>Note 2<\/strong>. The reaction with\u00a0<em>m<\/em>-CPBA is even more interesting. Epoxidation of an alkyne gives rise to a transient, very unstable <span style=\"color: #800080;\">(due to antiaromaticity &#8211; see\u00a0<em><a style=\"color: #800080;\" href=\"https:\/\/www.masterorganicchemistry.com\/2017\/03\/27\/antiaromaticity\/\">Antiaromatic Compounds And Antiaromaticity<\/a>)\u00a0<\/em><\/span><strong>oxirene<\/strong>, which quickly rearranges to an alpha-keto carbene. The carbene can then perform C-H insertion reactions on adjacent alkyl groups, such as <em>t<\/em>-butyl.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-41556\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F2-mcpba-oxidation-of-alkyne-gives-transient-oxirene-followed-by-rearrangement-to-carbene-c-h-insertion-shrunk.jpeg\" alt=\"mcpba oxidation of alkyne gives transient oxirene followed by rearrangement to carbene c-h insertion shrunk\" width=\"640\" height=\"408\" srcset=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F2-mcpba-oxidation-of-alkyne-gives-transient-oxirene-followed-by-rearrangement-to-carbene-c-h-insertion-shrunk.jpeg 1404w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F2-mcpba-oxidation-of-alkyne-gives-transient-oxirene-followed-by-rearrangement-to-carbene-c-h-insertion-shrunk-300x191.jpeg 300w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F2-mcpba-oxidation-of-alkyne-gives-transient-oxirene-followed-by-rearrangement-to-carbene-c-h-insertion-shrunk-1024x653.jpeg 1024w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F2-mcpba-oxidation-of-alkyne-gives-transient-oxirene-followed-by-rearrangement-to-carbene-c-h-insertion-shrunk-768x490.jpeg 768w, https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2025\/07\/F2-mcpba-oxidation-of-alkyne-gives-transient-oxirene-followed-by-rearrangement-to-carbene-c-h-insertion-shrunk-760x485.jpeg 760w\" sizes=\"(max-width: 640px) 100vw, 640px\" \/><\/a><\/p>\n<p>Reactions with cyclic alkynes are even more wild, with transannular C-H insertions to form various bicycles. See <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja00791a035\">JACS 1973<em>, 95<\/em>, 3284.\u00a0<\/a><\/p>\n<hr \/>\n<h2><strong><a id=\"quizzes\"><\/a>Quiz Yourself!<\/strong><\/h2>\n<p>[quizzes]<\/p>\n<hr \/>\n<h2><strong><a id=\"references\"><\/a>(Advanced) References and Further Reading<\/strong><\/h2>\n<p>Ozonolysis of alkynes is not commonly performed and tracking down good examples required more than the usual amount of detective work.<\/p>\n<p>Good leading reference is in Patai&#8217;s Chemistry of Triple Bonded Functional Groups&#8221; Supplement C Part 1 chapt 13, p. 523-524. (Laszlo I. Simandi).<\/p>\n<ol>\n<li><strong>THE OZONIZATION OF TRIPLE BONDS<\/strong><br \/>\nCHARLES D. HURD and ROBERT E. CHRIST<br \/>\n<em>The Journal of Organic Chemistry<\/em> <strong>1936<\/strong> 01 (2), 141-145<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo01231a002\">10.1021\/jo01231a002\u00a0<\/a><br \/>\nOne of the first published studies of the ozonolysis of triple bonds, with\u00a0 yields in the 45-60% range.<\/li>\n<li><strong>Transformations of alkynes to carboxylic acids and their derivatives via CC bond cleavage<br \/>\n<\/strong>Shivalinga Kollea and Sanjay Batra<br \/>\n<em>Org. Biomol. Chem<\/em>., <strong>2016,14<\/strong>, 11048-11060<br \/>\n<strong>DOI: <\/strong><a href=\"https:\/\/doi.org\/10.1039\/C6OB01912A\">10.1039\/C6OB01912A<\/a><br \/>\nA historical review on carbon-carbon triple bond cleavage and reactions, including ozonolysis, KMnO4, and many other reagents.<\/li>\n<li><strong>The Isolation of 1,2-Diketones from the Ozonization of Disubstituted Acetylenes<\/strong><br \/>\nThomas L. Jacobs<br \/>\n<em>Journal of the American Chemical Society<\/em> <strong>1936<\/strong> 58 (11), 2272-2273<br \/>\n<strong>DOI:<\/strong> <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja01302a053\">10.1021\/ja01302a053<\/a><\/li>\n<li><strong>Ozonolysis of Unsymmetrical Acetylenes<\/strong><br \/>\nPHILIP S. BAILEY, YUN-GER CHANG, and W. W. L. KWIE<br \/>\n<em>The Journal of Organic Chemistry<\/em> <strong>1962<\/strong> 27 (4), 1198-1201<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo01051a017\">10.1021\/jo01051a017\u00a0<\/a><\/li>\n<li><strong>Ozonolysis of Alkynes\u2014A Flexible Route to Alpha-Diketones: Synthesis of AI-2<\/strong><br \/>\nJoshua L. Alterman, Dua X. Vang, Marissa Roghair Stroud, Larry J. Halverson, and George A. Kraus<br \/>\n<em>Organic Letters<\/em> <strong>2020<\/strong> 22 (19), 7424-7426<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/acs.orglett.0c02182\">10.1021\/acs.orglett.0c02182\u00a0<\/a><br \/>\nA relatively recent application of alkyne ozonolysis, to obtain 1,2-diketones.<\/li>\n<li><strong>Reductive trapping in the ozonolysis of diphenylacetylene<\/strong><br \/>\nS. Jackson and L. A. Hull<br \/>\n<em>The Journal of Organic Chemistry<\/em> <strong>1976<\/strong> 41 (20), 3340-3342<br \/>\n<strong>DOI:<\/strong> <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo00882a037\">10.1021\/jo00882a037\u00a0<\/a><br \/>\nThe authors study the ozonolysis of diphenylacetylene and propose a mechanism for the formation of carboxylic acids similar to that for the ozonolysis of alkenes.<\/li>\n<li><strong>Ozonization and Oxidation of Stearolic Acid to 9, 10-Diketostearic Acid<\/strong><br \/>\nN. A. Khan and Melvin S. Newman<br \/>\n<em>The Journal of Organic Chemistry<\/em> <strong>1952<\/strong> 17 (7), 1063-1065<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo50007a024\">10.1021\/jo50007a024<\/a><br \/>\nThis study by Melvin &#8220;Newman Projection&#8221; Newman shows that actylenes can be oxidized to diketones at mildly basic pH (7.5) but will be cleaved to diacids at either strongly acidic or strongly basic pH.<\/li>\n<li><strong>Potassium permanganate oxidations of terminal olefins and acetylenes to carboxylic acids of one less carbon<\/strong><br \/>\nA. Paul Krapcho, James R. Larson, and Joyce M. Eldridge<br \/>\n<em>The Journal of Organic Chemistry<\/em> <strong>1977<\/strong> 42 (23), 3749-3753<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo00443a026\">10.1021\/jo00443a026<\/a><\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>Oxidation of Alkynes with Ozone and KMnO4 As we&#8217;ve seen previously, alkenes (olefins) can be oxidized to carbonyl compounds (aldehydes, ketones, carboxylic acids) with ozone <\/p>\n","protected":false},"author":1,"featured_media":15087,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1419],"tags":[169,477,880,552,524,570,233,563,808,528],"post_folder":[],"class_list":["post-7371","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-alkyne-reactions","tag-alkenes","tag-alkynes-2","tag-anti","tag-hydroboration","tag-lindlar","tag-mcpba","tag-mechanisms-2","tag-oso4","tag-sodium","tag-syn"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Reactions of Alkynes: Hydrogenation, Hydroboration, Cyclopropanation<\/title>\n<meta name=\"description\" content=\"How do the reactions of alkynes compare to the reactions of alkenes, especially with regard to the &quot;concerted pathway&quot;. 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