{"id":1649,"date":"2011-06-17T09:20:34","date_gmt":"2011-06-17T14:20:34","guid":{"rendered":"https:\/\/www.masterorganicchemistry.com\/?p=1649"},"modified":"2025-12-12T03:46:07","modified_gmt":"2025-12-12T09:46:07","slug":"reagent-friday-m-cpba-meta-chloroperoxybenzoic-acid","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2011\/06\/17\/reagent-friday-m-cpba-meta-chloroperoxybenzoic-acid\/","title":{"rendered":"m-CPBA (meta-chloroperoxybenzoic acid)"},"content":{"rendered":"<p><strong>m-Chloroperoxybenzoic Acid (<em>m<\/em>-CPBA) For The Epoxidation of Alkenes<\/strong><\/p>\n<ul>\n<li><em>m<\/em>-CPBA (<em>meta<\/em>-chloroperoxybenzoic acid) is a useful reagent for the formation of epoxides from alkenes (<span style=\"color: #993366;\"><em>note &#8211; often just called, m-chloro<strong>per<\/strong>benzoic acid, without the &#8220;oxy&#8221;<\/em><\/span>)<\/li>\n<li>In this reaction, the C-C pi bond is broken, and\u00a0 two new C-O single bonds are formed on the same face of the alkene pi-bond.\u00a0 Since both bonds are formed on the same face, this is an example of a <strong>syn<\/strong> addition.<\/li>\n<li>The weak O-O bond in <em>m<\/em>-CPBA is also broken. The -OH of the peroxyacid is the source of the oxygen in the new epoxide<\/li>\n<li>Epoxidation of alkenes with <em>m-<\/em>CPBA is an example of a\u00a0<strong>stereospecific\u00a0<\/strong>reaction. The configuration of atoms about the C\u2013C bond is always conserved. The reaction proceeds through a concerted transition state.<\/li>\n<li>Other peroxyacids such as peracetic acid, perbenzoic acid, and trifluoroperacetic acid are also effective reagents for epoxidation of alkenes.<\/li>\n<li>Alkynes <strong>do not<\/strong> undergo reaction with <em>m<\/em>-CPBA to give epoxides<\/li>\n<li><em>m-<\/em>CPBA is also useful for the Baeyer-Villiger oxidation, a reaction that converts ketones to esters [<span style=\"color: #993366;\"><em>for more on this, see post &#8211; <a href=\"https:\/\/www.masterorganicchemistry.com\/2018\/10\/08\/nitration-baeyer-villiger\/\">The Baeyer-Villiger Reaction<\/a><\/em><\/span>]<\/li>\n<\/ul>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-34549\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2011\/06\/0-summary-epoxidation-of-alkenes-with-mcpba-peroxyacids.gif\" alt=\"summary-epoxidation of alkenes with mcpba peroxyacids\" width=\"640\" height=\"585\" \/><\/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\">Epoxidation of Alkenes With Peroxyacids<\/a><\/li>\n<li><a href=\"#two\">Epoxidation of Alkenes Is Stereospecific<\/a><\/li>\n<li><a href=\"#three\">Mechanism for the Epoxidation of Alkenes<\/a><\/li>\n<li><a href=\"#four\">Which Alkene Will React?<\/a><\/li>\n<li><a href=\"#five\">Stereoselectivity<\/a><\/li>\n<li><a href=\"#six\">Other Epoxidation Reagents<\/a><\/li>\n<li><a href=\"#seven\">Sharpless Asymmetric Epoxidation<\/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. Epoxidation of Alkenes With Peroxyacids<\/h2>\n<p>When alkenes are treated with peroxyacids such as\u00a0<em>meta<\/em>-chloroperoxybenzoic acid (<em>m<\/em>-CPBA), two new C-O bonds are formed and a C-C pi bond is broken, resulting in the formation of an epoxide. (<span style=\"color: #993366;\"><em>An O\u2013O bond from m-CPBA is also broken, which is the source of the oxygen in the epoxide. The byproduct is\u00a0m-chlorobenzoic acid<\/em><\/span>).<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-34532\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/1-structure-of-meta-chloroperoxybenzoic-acid-mcpba-and-example-of-an-epoxidation-reaction.gif\" alt=\"structure of meta chloroperoxybenzoic acid mcpba and example of an epoxidation reaction\" width=\"640\" height=\"380\" \/><\/a><\/p>\n<p>Epoxides, also known as oxiranes, are 3-membered cyclic ethers. Since the inner bond angles of epoxides (approximately 60\u00b0) deviate significantly from the preferred tetrahedral geometry around carbon (109.5\u00b0) , they possess considerable <strong>ring<\/strong> <strong>strain<\/strong> (about 13 kcal\/mol) and undergo a large number of useful ring-opening reactions with nucleophiles. (<span style=\"color: #993366;\"><em>For more on the reactions of epoxides, see <a style=\"color: #993366;\" href=\"https:\/\/www.masterorganicchemistry.com\/2015\/01\/26\/epoxides-the-outlier-of-the-ether-family\">Epoxides &#8211; the Outlier of the Ether Family<\/a><\/em><\/span>]<\/p>\n<p>Epoxidation of alkenes with peroxyacids such as <em>m<\/em>-CPBA always occurs in such a way that both C-O bonds are formed on the <strong>same<\/strong> face of the alkene, an outcome known as &#8220;<em>syn<\/em> addition&#8221;.<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-34533\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/2-reaction-of-mcpba-with-an-alkene-in-an-epoxidation-reaction-showing-syn-addition.gif\" alt=\"reaction of mcpba with an alkene in an epoxidation reaction showing syn addition\" width=\"640\" height=\"317\" \/><\/a><\/p>\n<p>You can tell that addition is\u00a0<em>syn\u00a0<\/em>here because the new C-O bonds are <strong>both<\/strong> drawn as &#8220;<strong>wedges<\/strong>&#8221; (pointing <strong>out<\/strong> of the page) or &#8220;<strong>dashes<\/strong>&#8221; (pointing <strong>into<\/strong> the page).<\/p>\n<p>In this case both of these products are identical, since rotating the molecule 180\u00b0 results in the same product (see below)<\/p>\n<p><iframe class=\"giphy-embed\" src=\"https:\/\/giphy.com\/embed\/ViOu0VuOmo7zsoi6iN\" width=\"480\" height=\"270\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p><a href=\"https:\/\/giphy.com\/gifs\/ViOu0VuOmo7zsoi6iN\">via GIPHY<\/a> (<span style=\"color: #993366;\"><em>Look at how unhappy those plastic pieces are &#8211; the model kit really helps you visualize the ring strain :- )<\/em><\/span> )<\/p>\n<p>In many other cases this will result in the formation of a pair of enantiomers or diasteromers, depending on the structure of the starting alkene.<\/p>\n<p>Epoxidation of alkenes with peroxyacids <strong>never<\/strong> results in <em>anti<\/em> addition.<\/p>\n<p>It is\u00a0<em>incorrect<\/em> to draw the product of this epoxidation reaction as having one &#8220;wedge&#8221; C-O and one &#8220;dash&#8221; C-O, since this would represent\u00a0<em>anti<\/em> addition.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34534\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/4-epoxidation-never-gives-the-anti-products-as-these-would-be-impossibly-strained.gif\" alt=\"epoxidation never gives the anti products as these would be impossibly strained\" width=\"640\" height=\"298\" \/><\/a><\/p>\n<p>(<span style=\"color: #993366;\"><em>BTW if you try to make a model, you will see that this outcome would also be impossibly strained<\/em><\/span>)<\/p>\n<h2><a id=\"two\"><\/a>2. Epoxidation of Alkenes Is Stereospecific<\/h2>\n<p>In epoxidation reactions, the configuration of atoms about the alkene is always <strong>conserved<\/strong>.<\/p>\n<p>For example, the\u00a0<em>trans\u00a0<\/em>alkene below gives\u00a0<strong>only<\/strong> the\u00a0<em>trans <\/em>product\u00a0(as an equal mixture of enantiomers). Note that in product <strong>A<\/strong>, the <em>trans<\/em> arrangement of C\u2013H bonds about the C\u2013C bond has been conserved.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34535\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/5-epoxidation-of-alkenes-is-stereospectific-with-mcpba-mixture-of-geometric-isomers-gives-mixture-of-diastereomers.gif\" alt=\"epoxidation of alkenes is stereospectific with mcpba - mixture of geometric isomers gives mixture of diastereomers\" width=\"640\" height=\"319\" \/><\/a><\/p>\n<p>The product <strong>B<\/strong> where the two C-H bonds are\u00a0<em>cis\u00a0<\/em>to the C-C bond is not formed. (<em><span style=\"color: #993366;\">Note that this product\u00a0<strong>B<\/strong> would be the diastereomer of product\u00a0<strong>A<\/strong><\/span>)<\/em>.<\/p>\n<p>Likewise, the\u00a0<em>cis<\/em> alkene gives only product\u00a0<strong>B<\/strong>. (<span style=\"color: #993366;\"><em>Product <strong>A, <\/strong>diastereomers of product <strong>B<\/strong>, are <strong>not<\/strong> formed<\/em><\/span>.)<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34536\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/6-another-example-of-a-stereospecific-epoxidation-reaction-with-a-cis-alkene-giving-only-the-cis-product.gif\" alt=\"another example of a stereospecific epoxidation reaction with a cis alkene giving only the cis product\" width=\"640\" height=\"379\" \/><\/a><\/p>\n<p>Since the starting <em>trans<\/em> and\u00a0<em>cis<\/em> alkenes differ only in their configuration but yield products which are stereoisomers, epoxidation of alkenes is therefore an example of a <strong>stereospecific\u00a0<\/strong>reaction. [<span style=\"color: #993366;\"><em>see <a style=\"color: #993366;\" href=\"https:\/\/goldbook.iupac.org\/terms\/view\/S05994#:~:text=A%20reaction%20is%20termed%20stereospecific,stereoselective\">IUPAC<\/a> for the definition, also see article: <a href=\"https:\/\/www.masterorganicchemistry.com\/2010\/07\/02\/stereoselective-stereospecific\/\">Stereoselective and Stereospecific Reactions<\/a><\/em><\/span>]<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"34748\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"34748\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"34748\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"34748\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-34748\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-34748 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"34748\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-j109k\" data-id=\"j109k\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2486-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2486-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<h2><a id=\"three\"><\/a>3. The Mechanism of Epoxidation of Alkenes With\u00a0<em>m-<\/em>CPBA<\/h2>\n<p>Now that we&#8217;ve identified the bonds that form and break, and the expected stereochemistry for this reaction, we can start to ask ourselves how this reaction actually <em>works<\/em>.<\/p>\n<p>First of all: which oxygen from\u00a0<em>m<\/em>-CPBA is transferred to give the epoxide?<\/p>\n<p>Isotopic labelling studies can verify that the oxygen of the epoxide comes from the <strong>OH<\/strong> of the peroxyacid, <strong>not<\/strong> the interior O connected to the C=O.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34537\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/9-the-source-of-oxygen-in-the-epoxide-is-the-OH-group-of-the-mcpba.gif\" alt=\"the source of oxygen in the epoxide is the OH group of the mcpba\" width=\"640\" height=\"305\" \/><\/a><\/p>\n<p>One driving force for the reaction is breakage of the relatively weak O\u2013O and C-C pi bonds (bond dissocation energies of about 45 kcal\/mol and 60 kcal\/mol, respectively) in exchange for two relatively strong C-O sigma bonds (about 90 kcal\/mol).<\/p>\n<p>The transition state that has been proposed for the reaction of <em>m<\/em>-CPBA (and other peroxyacids) with alkenes has become known as the &#8220;butterfly mechanism&#8221;, owing to the\u00a0<em>four(!)\u00a0<\/em>partial bonds around the central oxygen that give the appearance of a large-winged insect.<\/p>\n<figure id=\"attachment_34538\" aria-describedby=\"caption-attachment-34538\" style=\"width: 640px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-34538\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/10-butterfly-transition-state-model-for-epoxidation-of-alkenes-using-mcpba.gif\" alt=\"butterfly transition state model for epoxidation of alkenes using mcpba\" width=\"640\" height=\"250\" \/><\/a><figcaption id=\"caption-attachment-34538\" class=\"wp-caption-text\"><span style=\"color: #993366;\"><em>Butterfly drawing by DALL-E<\/em><\/span><\/figcaption><\/figure>\n<p>This reaction gets my vote for the busiest one-step arrow-pushing mechanism in all of introductory organic chemistry:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34539\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/11-drawing-of-the-mechanism-and-transition-state-of-an-epoxidation-reaction-in-the-butterfly-model-with-mcpba-.gif\" alt=\"drawing of the mechanism and transition state of an epoxidation reaction in the butterfly model with mcpba\" width=\"640\" height=\"257\" \/><\/a><\/p>\n<p>Let&#8217;s break down everything that happens here in this <strong>one<\/strong> (!) step:<\/p>\n<ul>\n<li>The C\u2013C pi bond breaks<\/li>\n<li>Two new C\u2013O single bonds form<\/li>\n<li>The (weak) O\u2013OH bond breaks<\/li>\n<li>Meanwhile, the resulting carboxylic acid is transposed: a new C\u2013O pi bond forms, while the existing C-O pi bond acts as a base to remove a proton from the terminal oxygen.<\/li>\n<\/ul>\n<p>This &#8220;butterfly&#8221; mechanism accounts for the following experimental observations:<\/p>\n<ul>\n<li>The reaction is first-order in both peroxyacid and alkene (<span style=\"color: #993366;\"><em>second order overall<\/em><\/span>)<\/li>\n<li>The rate of reaction is not sensitive to the polarity of the solvent (<span style=\"color: #993366;\"><em>making a charged carbocation intermediate unlikely<\/em><\/span>) [<a href=\"#noteone\"><span style=\"color: #ff0000;\">Note 1<\/span><\/a>]<\/li>\n<\/ul>\n<p>It also accounts for the stereospecificity of the reaction. We would <strong>not<\/strong> expect a reaction that proceeds through a carbocation intermediate to be stereospecific, for example.\u00a0 (<span style=\"color: #993366;\"><em>The reaction of HCl with alkenes is not stereospecific, for example)<\/em><\/span><\/p>\n<p>Two additional facts are worth noting.<\/p>\n<ul>\n<li>Electron-rich alkenes react more quickly than electron poor alkenes [<span style=\"color: #993366;\"><a style=\"color: #993366;\" href=\"#refsix\">Ref<\/a><\/span>], and<\/li>\n<li>adding electron-withdrawing groups to the R group of the peroxyacid make it more reactive. (<span style=\"color: #800080;\"><em>The added chlorine on the 3-position of the benzene ring makes it more electron-withdrawing and therefore more reactive, relative to plain-ol&#8217; peroxybenzoic acid).\u00a0<\/em><\/span><\/li>\n<\/ul>\n<h2><a id=\"four\"><\/a>4. Which Alkene Will React?<\/h2>\n<p>Let&#8217;s imagine we have a molecule containing multiple C-C pi bonds that is treated with <em>m<\/em>-CPBA.<\/p>\n<p>Is it possible to get epoxidation to happen at just one alkene pi-bond, or do we just end up with a mixture of products?<\/p>\n<p>What is observed is that the most <strong>electron-rich<\/strong> alkene undergoes epoxidation <strong>first<\/strong>, with remarkably good selectivity.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34540\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/12-the-epoxidation-of-alkenes-with-mcpba-is-regioselective-for-the-more-substituted-alkene-more-electron-rich.gif\" alt=\"-the epoxidation of alkenes with mcpba is regioselective for the more substituted alkene - more electron rich\" width=\"640\" height=\"420\" \/><\/a><\/p>\n<p>&#8220;Most electron-rich&#8221; generally means the alkene which has the most carbon atoms directly attached to the alkene (<span style=\"color: #993366;\"><em>i.e. &#8220;most substituted&#8221;<\/em><\/span>) so long as they are not electron-withdrawing groups.<\/p>\n<p>For instance, in the alkene above, it&#8217;s the trisubstituted alkene preferentially undergoes epoxidation while the mono-substituted alkene is untouched.<\/p>\n<p>This might seem counter-intuitive since we might expect that a more substituted alkene is more sterically hindered, but in practice the rate of reaction is more sensitive to electronic effects (i.e. electron-rich vs. electron-poor) than steric effects. [<a href=\"#notetwo\">Note 2<\/a>] [<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/0040402076801378\">Ref<\/a>]<\/p>\n<p>See if you can apply this concept in the question below:<\/p>\n<div class=\"wq-quiz-wrapper\" data-id=\"34747\"><style type=\"text\/css\" id=\"wq-flip-custom-css\">.wq-quiz-wrapper[data-id=\"34747\"] {\n--wq-question-width: 100%;\n--wq-question-color: #009cff;\n--wq-question-height: auto;\n--wq-font-color: #444;\n}\n\n\t\t\t.wq-quiz-wrapper[data-id=\"34747\"] {\n\t\t\t\t--wq-question-width: 600px;\n\t\t\t}\n\n\t\t\t@media screen and (max-width: 600px) {\n\t\t\t\t.wq-quiz-wrapper[data-id=\"34747\"] .wq_singleQuestionWrapper { width:100% !important; height:auto !important; }\n\t\t\t}\n\t\t<\/style><!-- wp quiz -->\n<div id=\"wp-quiz-34747\" class=\"wq_quizCtr single flip_quiz wq-quiz wq-quiz-34747 wq-quiz-flip wq-layout-single wq-skin-traditional wq-should-show-correct-answer\" data-quiz-id=\"34747\">\n<div class=\"wq-questions wq_questionsCtr\">\n\t<div class=\"wq-question wq_singleQuestionWrapper wq-question-texd2\" data-id=\"texd2\">\n\n\t\n\t<div class=\"item_top\">\n\t\t<div class=\"title_container\">\n\t\t\t<div class=\"wq_questionTextCtr\">\n\t\t\t\t<h4 class=\"wq-question-title\"><\/h4>\n\t\t\t<\/div>\n\t\t<\/div>\n\t<\/div>\n\n\t<div class=\"card \">\n\t\t<div class=\"front\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2488-Front.gif\" \/>\n\t\t\n\t\t\n\t\n\t\n\t\t\t<span class=\"top-desc\">Click to Flip<\/span>\n\t<\/div>\n\t\t<div class=\"back\" >\n\t\n\t\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-images\/2488-Reverse.gif\" \/>\n\t\t\n\t\t\n\t\n\t<\/div>\n\t<\/div>\n\n\t\n<\/div>\n<\/div>\n<\/div>\n<!-- \/\/ wp quiz-->\n<\/div><!-- End .wq-quiz-wrapper -->\n<h2><a id=\"five\"><\/a>5. Stereoselectivity<\/h2>\n<p>When epoxidation is performed on an alkene containing pre-existing chiral centers, then there is the potential for the formation of stereoisomers. That&#8217;s because the two faces of the alkene will not be equivalent steric environments, as seen from the perspective of electrophile (such as <em>m<\/em>-CPBA).<\/p>\n<p>A particularly striking example is the bicyclic alkene below. When it is treated with\u00a0<em>m<\/em>-CPBA, a 99:1 mixture of products (diastereomers)\u00a0 is formed. The reason for the high selectivity is that the electrophile (<em>m<\/em>-CPBA) only encounters a single CH<sub>2<\/sub> group in its approach to the top face (favored), whereas it encounters a two-carbon bridge in is approach on the bottom face (disfavored).<\/p>\n<p>In this case, the result is a 99:1 ratio of products favoring attack on the least hindered face of the alkene.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34541\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/14-epoxidation-of-an-alkene-with-mcpba-on-a-bridged-bicyclic-compound-showing-excellent-facial-selectivity.gif\" alt=\"epoxidation of an alkene with mcpba on a bridged bicyclic compound showing excellent facial selectivity\" width=\"640\" height=\"441\" \/><\/a><\/p>\n<p><span style=\"color: #993366;\"><em>There is a more systematic method for naming faces of alkenes, (<a style=\"color: #993366;\" href=\"https:\/\/en.wikipedia.org\/wiki\/Prochirality\">known as Re\u00a0and\u00a0Si<\/a> ) which we will not get into at present.\u00a0<\/em><\/span><\/p>\n<h2><a id=\"six\"><\/a>6. Other Epoxidation Reagents<\/h2>\n<p>Other peroxyacids have been used for epoxidation reactions, such as peroxyacetic acid, peroxybenzoic acid, and trifluoroperoxyacetic acid.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34542\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/15-other-reagents-for-epoxidation-reactions-include-perbenzoic-acid-peroxyacetic-acid-and-dmdo.gif\" alt=\"other reagents for epoxidation reactions include perbenzoic acid, peroxyacetic acid, and dmdo\" width=\"640\" height=\"296\" \/><\/a><\/p>\n<p>Just as making the alkene more electron-rich increases the rate of reaction, it has also been observed that adding electron-withdrawing reagents to the electrophile (peroxyacid) increases the rate of reaction.<\/p>\n<p>The epoxidation of alkenes with peroxyacids has been known since 1909, but it was only in the 1960s that\u00a0<em>m<\/em>-CPBA started gaining widespread use, which greatly improved the scope of epoxidation reactions. [<a href=\"#notethree\"><span style=\"color: #ff0000;\">Note 3<\/span><\/a>]<\/p>\n<p>Furthermore, although they aren&#8217;t often covered in introductory courses, there are other ways of epoxidizing alkenes that don&#8217;t involve peroxyacids. Examples include metals such as vanadium, titanium, manganese and others in the presence of peroxides (<span style=\"color: #993366;\"><em>or hydroperoxides<\/em><\/span>), or the use of reagents such as dimethyldioxirane (DMDO).<\/p>\n<h2><a id=\"seven\"><\/a>7. Sharpless Asymmetric Epoxidation<\/h2>\n<p>Enantioselective epoxidation of alkenes is also a known process.<\/p>\n<p>In an enantioselective reaction, one starts with an achiral molecule and adds a chiral reagent that selectively attacks one face of the starting material over the other, resulting in a mixture of products which is enriched in on enantiomer over another. (<span style=\"color: #993366;\"><em>One can&#8217;t just use\u00a0<strong>any<\/strong>\u00a0chiral reagent &#8211; there&#8217;s a lot of trial and error involved in getting the right recipe<\/em><\/span>) [Note]<\/p>\n<p>One prominent method for the enantioselective epoxidation of alkenes was developed by <a href=\"https:\/\/en.wikipedia.org\/wiki\/Karl_Barry_Sharpless\">K. Barry Sharpless<\/a> (<a href=\"https:\/\/www.scripps.edu\/\">Scripps<\/a>) and has become known as the Sharpless epoxidation.<\/p>\n<p>The Sharpless epoxidation involves treating an allylic alcohol with a witches&#8217; brew of titanium isopropoxide [Ti(O<em>i-<\/em>Pr)<sub>4<\/sub>)]\u00a0<em>t<\/em>-butylhydroperoxide (the oxidant) and, depending on which enantiomer is desired, either (<em>S,S)\u00a0<\/em>or (<em>R, R)\u00a0<\/em>diethyl tartrate (<span style=\"color: #993366;\"><em>or di-isopropyl tartrate, in some cases<\/em><\/span>)<\/p>\n<p>Here is a simple example.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-34544\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2023\/05\/16-example-of-Sharpless-epoxidation-of-allylic-alcohols-1.gif\" alt=\"example of Sharpless epoxidation of allylic alcohols\" width=\"640\" height=\"206\" \/><\/a><\/p>\n<p>The reaction is not enantioselective without the OH group on the carbon adjacent to the alkene. (<span style=\"color: #993366;\"><em>This class of molecules is known as &#8220;allylic alcohols&#8221;<\/em><\/span>).\u00a0 The hydroxyl group is required to coordinate to the titanium and direct the epoxidation.<\/p>\n<p>For much more on the Sharpless epoxidation, I highly recommend <a href=\"https:\/\/hwpi.harvard.edu\/files\/myers\/files\/22-sharpless_asymmetric_epoxidation_reaction.pdf\">these notes<\/a> (Chemistry 115, Harvard University, Prof. Andrew G. Myers).<\/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\/2015\/01\/26\/epoxides-the-outlier-of-the-ether-family\/\" class=\"\"><span>Epoxides \u2013 The Outlier Of The Ether Family<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2015\/02\/10\/opening-of-epoxide-with-base\/\" class=\"\"><span>Epoxide Ring Opening With Base<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2015\/02\/02\/opening-of-epoxides-with-acid\/\" class=\"\"><span>Opening of Epoxides With Acid<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/07\/01\/reagent-friday-oso4-osmium-tetroxide\/\" class=\"\"><span>OsO4 (Osmium Tetroxide) for Dihydroxylation of Alkenes<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2010\/07\/02\/stereoselective-stereospecific\/\" class=\"\"><span>Stereoselective and Stereospecific Reactions<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2018\/10\/08\/nitration-baeyer-villiger\/\" class=\"\"><span>More Reactions on the Aromatic Sidechain: Reduction of Nitro Groups and the Baeyer Villiger<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/05\/23\/whats-a-racemic-mixture\/\" class=\"\"><span>What\u2019s a Racemic Mixture?<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/04\/02\/epoxidation-hydroxylation-cyclopropanation-alkene-mechanism\/\" class=\"\"><span>Alkene Addition Pattern #3: The \u201cConcerted\u201d Pathway<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2014\/04\/03\/cycloalkanes-ring-strain-in-cyclopropane-and-cyclobutane\/\" class=\"\"><span>Cycloalkanes \u2013 Ring Strain In Cyclopropane And Cyclobutane<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2011\/11\/25\/palladium-on-carbon-pdc\/\" class=\"\"><span>Palladium on Carbon (Pd\/C) for Catalytic Hydrogenation<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/01\/22\/alkene-addition-regioselectivity-syn-anti\/\" class=\"\"><span>Alkene Addition Reactions: \u201cRegioselectivity\u201d and \u201cStereoselectivity\u201d (Syn\/Anti)<\/span><\/a><\/li><\/ul><\/div>\n<p>For this article, Encyclopedia of Reagents for Organic Synthesis was very useful [<a href=\"https:\/\/archive.org\/search?query=subject%3A%22Organic+compounds+--+Synthesis+--+Encyclopedias%22\">See on archive.org<\/a>] , as was March&#8217;s Advanced Organic Chemistry and Prof Andrew Myers&#8217; Chem 115 Notes (Harvard).<\/p>\n<p><a id=\"noteone\"><\/a><strong>Note 1<\/strong>.\u00a0 A typical solvent for epoxidation with <em>m<\/em>-CPBA is the relatively non-polar solvent dichloromethane. Interestingly, the rate of epoxidation is much slower in hydrogen-bonding solvents, as these tend to disrupt the internal hydrogen bonding of the &#8220;butterfly&#8221; transition state. [<a href=\"https:\/\/doi.org\/10.1021\/jo01030a078\">Ref<\/a>]<\/p>\n<p><strong><a id=\"notetwo\"><\/a>Note 2<\/strong>.\u00a0 This reminds me of an old joke among organic chemistry graduate students: if you&#8217;re asked at a group meeting to explain why a particular reaction happens (or doesn&#8217;t happen), the stock answer is, &#8220;a combination of electronics and sterics&#8221;. Covers all the bases!<\/p>\n<p><strong><a id=\"notethree\"><\/a>Note 3<\/strong>.\u00a0 The reactivity of <em>m<\/em>-CPBA is highly superior to that of peroxybenzoic acid, but only became widely available after 1963. For a comparison of the scope of peroxybenzoic acid and\u00a0<em>m<\/em>-CPBA, compare [<a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/jo01078a002\">Ref<\/a>] and [<a href=\"https:\/\/doi.org\/10.1021\/jo01030a078\">Ref<\/a>] &#8211;\u00a0<em>m-<\/em>CPBA gives cleaner and faster reactions, with greater scope. It is also a nicely crystalline white solid. Commercially available\u00a0<em>m-<\/em>CPBA consists of about 80%\u00a0<em>m<\/em>-CPBA with the remainder being\u00a0<em>m<\/em>-chlorobenzoic acid. It can be purified further by treating with a buffer, but great care should be taken with highly purified\u00a0<em>m<\/em>-CPBA due to its potentially explosive properties.<\/p>\n<p><strong><a id=\"notefour\"><\/a>Note 4.<\/strong> To give an idea of the trial and error involved in the development of this reaction, see Sharpless&#8217; <a href=\"https:\/\/www.nobelprize.org\/uploads\/2018\/06\/sharpless-lecture.pdf\">Nobel Lecture<\/a>. (the first one, in 2001, not the second one from 2022). The two full papers [<a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja00001a018\">here<\/a>] and [<a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja00001a019\">here<\/a>] on determining the mechanism of the reaction are classic examples of meticulous, systematic experimental work.<\/p>\n<hr \/>\n<h2><strong><a id=\"quiz\"><\/a>Quiz Yourself!<\/strong><\/h2>\n<p>Here&#8217;s a quiz on identifying the relationship between products of epoxidation reactions. (<span style=\"color: #993366;\"><em>Note &#8211; for more examples of these types of quizzes, see this post on &#8220;<a href=\"https:\/\/www.masterorganicchemistry.com\/2012\/05\/23\/whats-a-racemic-mixture\/\">What&#8217;s A Racemic Mixture<\/a>&#8220;.<\/em><\/span>)<br \/>\n<\/p>\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/2487-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<\/p>\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3059-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<\/p>\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3060-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. <\/p>\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\/3590-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. <\/p>\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\/3057-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<\/p>\n<p class=\"p1\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-26714\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3058-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. <\/p>\n<hr \/>\n<h2><strong><a id=\"references\"><\/a>(Advanced) References and Further Reading<\/strong><\/h2>\n<p><strong>(Advanced) References and Further Reading<\/strong><\/p>\n<ol>\n<li><strong>Oxydation unges\u00e4ttigter Verbindungen mittels organischer Superoxyde<br \/>\n<\/strong>Nikolaus Prileschaev<br \/>\n<em>Chem. Ber. <\/em><strong>1909, <\/strong><em>42<\/em>, 4811.<br \/>\n<strong>DOI:<\/strong> <a href=\"http:\/\/onlinelibrary.wiley.com\/doi\/10.1002\/cber.190904204100\/abstract\">10.1002\/cber.190904204100<\/a><br \/>\nThis reaction (epoxidations of alkenes with a peracid) is also known as the Prizelhaev reaction after the author.<\/li>\n<li><strong>The oxidation of olefins with perbenzoic acids. A kinetic study<br \/>\n<\/strong> M. Lynch and\u00a0 K. H. Pausacker.<br \/>\n<em>J. Chem. Soc.\u00a0<\/em><strong>1955<\/strong><em><a href=\"https:\/\/pubs.rsc.org\/en\/content\/articlelanding\/1955\/jr\/jr9550001525#!divAbstract\">, 1525-1531.<\/a><br \/>\n<\/em><strong>DOI:\u00a0<\/strong><a href=\"https:\/\/pubs.rsc.org\/en\/content\/articlelanding\/1955\/jr\/jr9550001525#!divAbstract\">10.1039\/JR9550001525<\/a><br \/>\nOne of the earliest papers on epoxidation with <em>m<\/em>-CPBA, comparing its reactivity with other substituted peracids. As expected, the reactivity of peroxyacids is increased by electron-withdrawing groups.<\/li>\n<li><strong>m-CHLOROPERBENZOIC ACID<br \/>\n<\/strong>Richard N. McDonald, Richard N. Steppel, and James E. Dorsey.<br \/>\n<em>Org. <\/em><em>Synth. <b>1970<\/b>,\u00a0<\/em>50, 15.<br \/>\n<strong>DOI: <\/strong><a href=\"https:\/\/orgsyn.org\/demo.aspx?prep=cv6p0276\">10.15227\/orgsyn.050.0015<\/a><br \/>\nA reliable preparation for <em>m<\/em>-CPBA (which is commercially available) in <em>Organic Syntheses.\u00a0<\/em>As this procedure shows, <em>m<\/em>-CPBA is not prepared as a pure compound (it is a mixture of the peracid and acid, and commercial samples may contain residual water for stability).<\/li>\n<li><strong>Epoxidations with m-Chloroperbenzoic Acid<br \/>\n<\/strong>Nelson N. Schwartz and John H. Blumbergs.<br \/>\n<em>J. Org. Chem.\u00a0<\/em><strong>1964\u00a0<\/strong><em>29,\u00a0<\/em>(7), 1976-1979.<br \/>\n<strong>DOI:\u00a0<\/strong><a href=\"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/jo01030a078\">1021\/jo01030a078<\/a><br \/>\nThis paper describes mechanistic studies of <em>m<\/em>-CPBA oxidation that demonstrate that ionic intermediates are not involved in the reaction, and that the rate is insensitive to solvent polarity.<\/li>\n<li><strong>Record of chemical progress<br \/>\n<\/strong>Bartlett, P. D.<br \/>\n<em>Chem. Prog<\/em>.\u00a01950,\u00a0<em>11<\/em>, 47<br \/>\n[<a href=\"https:\/\/catalog.hathitrust.org\/Record\/000519370\">Link<\/a>]<br \/>\nThis is the publication in which Prof. P. D. Bartlett describes the \u2018butterfly mechanism\u2019 for\u00a0<em>m-<\/em>CPBA epoxidation.<\/li>\n<li><strong><a id=\"refsix\"><\/a>MCPBA Epoxidation of Alkenes: Reinvestigation of Correlation between Rate and Ionization Potential<br \/>\n<\/strong>Cheal Kim, Teddy G. Traylor, and Charles L. Perrin.<br \/>\n<em>J. Am. Chem. Soc.\u00a0<\/em><strong>1998,\u00a0<\/strong><em>120,\u00a0<\/em>(37), 9513-9516.<br \/>\n<strong>DOI:\u00a0<\/strong><a href=\"https:\/\/pubs.acs.org\/doi\/abs\/10.1021\/ja981531e\">1021\/ja981531e<\/a><br \/>\nAn interesting paper that describes the development of a kinetic method for measuring the rate of epoxidation of various alkenes with <em>m<\/em>-CPBA.<\/li>\n<li><strong>Experimental Geometry of the Epoxidation Transition State<\/strong><br \/>\nDaniel A. Singleton, Steven R. Merrigan, Jian Liu, and K. N. Houk.<br \/>\n<em>J. Am. Chem. Soc.\u00a0<\/em><strong>1997,\u00a0<\/strong><em>119,\u00a0<\/em>(14), 3385-3386.<br \/>\n<strong>DOI:\u00a0<\/strong><a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja963656u\">1021\/ja963656u<\/a><br \/>\nCombined experimental and theoretical studies of the epoxidation transition state, showing that both C-O bond forming events are nearly synchronous.<\/li>\n<li><strong>The mechanism of epoxidation of olefins by peracids<\/strong><br \/>\nV. G. Dryuk.<br \/>\n<em>Tetrahedron. <\/em>Volume <em>32<\/em>, Issue 23, <strong>1976<\/strong>, 2855-2866.<br \/>\n<strong>DOI:<\/strong><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/0040402076801378\">10.1016\/0040-4020(76)80137-8<\/a><br \/>\nAn account of the author\u2019s work on kinetic studies of the epoxidation of olefins with peracids in order to determine the exact mechanism.<\/li>\n<li><strong>The Bond Dissociation Energy of Peroxides Revisited<\/strong><br \/>\nhttps:\/\/pubs.acs.org\/action\/showCitFormats?doi=10.1021\/acs.jpca.0c02859&amp;ref=pdf<\/li>\n<li><strong>The first practical method for asymmetric epoxidation<br \/>\n<\/strong>Tsutomu Katsuki and K. Barry Sharpless<br \/>\n<cite>Journal of the American Chemical Society<\/cite>\u00a0<strong>1980<\/strong>\u00a0<em>102<\/em>\u00a0(18), 5974-5976<br \/>\n<strong>DOI<\/strong>: <a href=\"https:\/\/pubs.acs.org\/doi\/10.1021\/ja00538a077\">10.1021\/ja00538a077<\/a><br \/>\nKatsuki and Sharpless&#8217; first report from 1980 on the asymmetric epoxidation reaction of allylic alcohols.<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>m-Chloroperoxybenzoic Acid (m-CPBA) For The Epoxidation of Alkenes m-CPBA (meta-chloroperoxybenzoic acid) is a useful reagent for the formation of epoxides from alkenes (note &#8211; often <\/p>\n","protected":false},"author":1,"featured_media":34549,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1418],"tags":[169,175,207,470,570,412,264,265,405],"post_folder":[],"class_list":["post-1649","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-alkene-reactions","tag-alkenes","tag-baeyer-villiger","tag-epoxidation","tag-epoxides","tag-mcpba","tag-reagent-friday","tag-reagent-guide-2","tag-reagents","tag-reagents-app"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>m-CPBA (meta-chloroperoxybenzoic acid)<\/title>\n<meta name=\"description\" content=\"mCPBA (meta-chloroperoxybenzoic acid) is a useful oxidant for the epoxidation of alkenes and for the Baeyer-Villiger oxidation of ketones to esters.\" \/>\n<meta name=\"robots\" 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