{"id":519,"date":"2018-11-26T15:56:57","date_gmt":"2018-11-26T15:56:57","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/?post_type=chapter&#038;p=519"},"modified":"2019-01-09T07:54:36","modified_gmt":"2019-01-09T07:54:36","slug":"15-2-protecting-groups","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/chapter\/15-2-protecting-groups\/","title":{"raw":"15.2 Use of protecting groups","rendered":"15.2 Use of protecting groups"},"content":{"raw":"<header class=\"elm-header\">\r\n<div class=\"elm-header-custom\">\r\n<div class=\"mt-container-secondary\"><span style=\"font-size: 1em\">A challenge organic chemists face in the laboratory when planning a transformation or modification of a functional group in a polyfunctional compound is the possibility of unintended changes in the other functional\u00a0groups\u00a0in lieu of or in addition to the intended change.<\/span><\/div>\r\n<\/div>\r\n<\/header><article id=\"elm-main-content\" class=\"elm-content-container\"><section class=\"mt-content-container\">eg: \u00a0Terminal alkyne <strong>1<\/strong> can be converted to internal alkyne <strong>2<\/strong> by treating <strong>1<\/strong> with a very strong base, such as <sup>\u2014<\/sup>NH<sub>2<\/sub>, followed by an ethyl substrate.<img class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155202\/protectinggroup1.png\" alt=\"\" width=\"600\" height=\"60\" \/>\r\n\r\n&nbsp;\r\n\r\nHowever, <strong>3<\/strong> can not be converted to <strong>4<\/strong> using the same two-reaction sequence.\r\n\r\n&nbsp;\r\n\r\n<img class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155205\/protectinggroup2.png\" alt=\"\" width=\"600\" height=\"48\" \/>\r\n\r\n&nbsp;\r\n\r\nIn <strong>3<\/strong>, the most acidic hydrogen atom is not the alkynyl hydrogen but the hydrogen atom in the alcohol group. \u00a0Consequently, treatment of <strong>3<\/strong> with the base results in the base deprotonating the alcohol group in <strong>3<\/strong> giving an alkoxide ion, which reacts with the substrate yielding <strong>5<\/strong>, not <strong>4<\/strong>, as the organic product.\r\n\r\n<img class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155208\/protectinggroup3.png\" alt=\"\" width=\"599\" height=\"225\" \/>\r\n\r\n&nbsp;\r\n\r\nIn order to convert <strong>3<\/strong> to <strong>4<\/strong> using the methodology employed to convert <strong>1<\/strong> to <strong>2<\/strong>,\u00a0the alcohol group in <strong>3<\/strong> must first be removed temporarily. \u00a0One way to do so is to convert the alcohol group into a silyl either group.\r\n\r\n&nbsp;\r\n\r\n<img class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155211\/protectinggroup4.png\" alt=\"\" width=\"599\" height=\"65\" \/>\r\n\r\n&nbsp;\r\n\r\nIn <strong>6<\/strong>, the most acidic hydrogen is the alkynyl hydrogen. \u00a0Treatment of <strong>6<\/strong> with \u00afNH<sub>2<\/sub>, followed by the substrate results in <strong>7<\/strong>.\r\n\r\n&nbsp;\r\n\r\n<img class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155215\/protectinggroup5.png\" alt=\"\" width=\"600\" height=\"87\" \/>\r\n\r\n&nbsp;\r\n\r\nReplacement of the silyl either group in <strong>7<\/strong> with the alcohol group yields <strong>4<\/strong>.\r\n\r\n&nbsp;\r\n\r\n<img class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155218\/protectinggroup6.png\" alt=\"\" width=\"592\" height=\"97\" \/>\r\n\r\n&nbsp;\r\n\r\nIn the overall reaction (\u2460+ \u2461+ \u2462), the silyl ether is said to act as the protecting group of the alcohol group; reaction \u2460 is known as the protection step and reaction \u2462 the deprotection step.\r\n<div id=\"section_1\" class=\"mt-section\">\r\n\r\n&nbsp;\r\n<h3 class=\"editable\">Contributors<\/h3>\r\n<ul>\r\n \t<li><a class=\"external\" title=\"http:\/\/www.uvu.edu\/profpages\/profiles\/show\/user_id\/1776\" href=\"http:\/\/www.uvu.edu\/profpages\/profiles\/show\/user_id\/1776\" target=\"_blank\" rel=\"external nofollow noopener\"><span class=\"gD\">Gamini Gunawardena<\/span><\/a> from the <a class=\"external\" title=\"http:\/\/science.uvu.edu\/ochem\/\" href=\"http:\/\/science.uvu.edu\/ochem\/\" target=\"_blank\" rel=\"external nofollow noopener\">OChemPal <\/a>site (<a class=\"external\" title=\"http:\/\/www.uvu.edu\/chemistry\/\" href=\"http:\/\/www.uvu.edu\/chemistry\/\" target=\"_blank\" rel=\"external nofollow noopener\">Utah Valley University<\/a>)<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/section><\/article>","rendered":"<header class=\"elm-header\">\n<div class=\"elm-header-custom\">\n<div class=\"mt-container-secondary\"><span style=\"font-size: 1em\">A challenge organic chemists face in the laboratory when planning a transformation or modification of a functional group in a polyfunctional compound is the possibility of unintended changes in the other functional\u00a0groups\u00a0in lieu of or in addition to the intended change.<\/span><\/div>\n<\/div>\n<\/header>\n<article id=\"elm-main-content\" class=\"elm-content-container\">\n<section class=\"mt-content-container\">eg: \u00a0Terminal alkyne <strong>1<\/strong> can be converted to internal alkyne <strong>2<\/strong> by treating <strong>1<\/strong> with a very strong base, such as <sup>\u2014<\/sup>NH<sub>2<\/sub>, followed by an ethyl substrate.<img loading=\"lazy\" decoding=\"async\" class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155202\/protectinggroup1.png\" alt=\"\" width=\"600\" height=\"60\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>However, <strong>3<\/strong> can not be converted to <strong>4<\/strong> using the same two-reaction sequence.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155205\/protectinggroup2.png\" alt=\"\" width=\"600\" height=\"48\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>In <strong>3<\/strong>, the most acidic hydrogen atom is not the alkynyl hydrogen but the hydrogen atom in the alcohol group. \u00a0Consequently, treatment of <strong>3<\/strong> with the base results in the base deprotonating the alcohol group in <strong>3<\/strong> giving an alkoxide ion, which reacts with the substrate yielding <strong>5<\/strong>, not <strong>4<\/strong>, as the organic product.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155208\/protectinggroup3.png\" alt=\"\" width=\"599\" height=\"225\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>In order to convert <strong>3<\/strong> to <strong>4<\/strong> using the methodology employed to convert <strong>1<\/strong> to <strong>2<\/strong>,\u00a0the alcohol group in <strong>3<\/strong> must first be removed temporarily. \u00a0One way to do so is to convert the alcohol group into a silyl either group.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155211\/protectinggroup4.png\" alt=\"\" width=\"599\" height=\"65\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>In <strong>6<\/strong>, the most acidic hydrogen is the alkynyl hydrogen. \u00a0Treatment of <strong>6<\/strong> with \u00afNH<sub>2<\/sub>, followed by the substrate results in <strong>7<\/strong>.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155215\/protectinggroup5.png\" alt=\"\" width=\"600\" height=\"87\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>Replacement of the silyl either group in <strong>7<\/strong> with the alcohol group yields <strong>4<\/strong>.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"internal aligncenter\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3773\/2018\/11\/26155218\/protectinggroup6.png\" alt=\"\" width=\"592\" height=\"97\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>In the overall reaction (\u2460+ \u2461+ \u2462), the silyl ether is said to act as the protecting group of the alcohol group; reaction \u2460 is known as the protection step and reaction \u2462 the deprotection step.<\/p>\n<div id=\"section_1\" class=\"mt-section\">\n<p>&nbsp;<\/p>\n<h3 class=\"editable\">Contributors<\/h3>\n<ul>\n<li><a class=\"external\" title=\"http:\/\/www.uvu.edu\/profpages\/profiles\/show\/user_id\/1776\" href=\"http:\/\/www.uvu.edu\/profpages\/profiles\/show\/user_id\/1776\" target=\"_blank\" rel=\"external nofollow noopener\"><span class=\"gD\">Gamini Gunawardena<\/span><\/a> from the <a class=\"external\" title=\"http:\/\/science.uvu.edu\/ochem\/\" href=\"http:\/\/science.uvu.edu\/ochem\/\" target=\"_blank\" rel=\"external nofollow noopener\">OChemPal <\/a>site (<a class=\"external\" title=\"http:\/\/www.uvu.edu\/chemistry\/\" href=\"http:\/\/www.uvu.edu\/chemistry\/\" target=\"_blank\" rel=\"external nofollow noopener\">Utah Valley University<\/a>)<\/li>\n<\/ul>\n<\/div>\n<\/section>\n<\/article>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-519\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Protecting Group. <strong>Authored by<\/strong>: Gamini Gunawardena. <strong>Provided by<\/strong>: Utah Valley University. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/chem.libretexts.org\/Ancillary_Materials\/Reference\/Organic_Chemistry_Glossary\/Protecting_Group\">https:\/\/chem.libretexts.org\/Ancillary_Materials\/Reference\/Organic_Chemistry_Glossary\/Protecting_Group<\/a>. <strong>Project<\/strong>: Chemistry LibreTexts. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA: Attribution-NonCommercial-ShareAlike<\/a><\/em><\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":311,"menu_order":2,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Protecting Group\",\"author\":\"Gamini Gunawardena\",\"organization\":\"Utah Valley University\",\"url\":\"https:\/\/chem.libretexts.org\/Ancillary_Materials\/Reference\/Organic_Chemistry_Glossary\/Protecting_Group\",\"project\":\"Chemistry LibreTexts\",\"license\":\"cc-by-nc-sa\",\"license_terms\":\"\"}]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-519","chapter","type-chapter","status-publish","hentry"],"part":507,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/pressbooks\/v2\/chapters\/519","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/wp\/v2\/users\/311"}],"version-history":[{"count":7,"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/pressbooks\/v2\/chapters\/519\/revisions"}],"predecessor-version":[{"id":3078,"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/pressbooks\/v2\/chapters\/519\/revisions\/3078"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/pressbooks\/v2\/parts\/507"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/pressbooks\/v2\/chapters\/519\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/wp\/v2\/media?parent=519"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/pressbooks\/v2\/chapter-type?post=519"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/wp\/v2\/contributor?post=519"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-potsdam-organicchemistry2\/wp-json\/wp\/v2\/license?post=519"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}