{"id":241781,"date":"2025-07-04T03:32:22","date_gmt":"2025-07-04T03:32:22","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=241781"},"modified":"2025-07-04T03:32:24","modified_gmt":"2025-07-04T03:32:24","slug":"starting-with-the-ester-shown-below-synthesize-a-ketoester-hydrolyze-ester-back-to-the-carboxylic-acid-and-perform-the-decarboxylation","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/07\/04\/starting-with-the-ester-shown-below-synthesize-a-ketoester-hydrolyze-ester-back-to-the-carboxylic-acid-and-perform-the-decarboxylation\/","title":{"rendered":"Starting with the ester shown below, synthesize a ?-ketoester, hydrolyze ester back to the carboxylic acid, and perform the decarboxylation"},"content":{"rendered":"\n

Starting with the ester shown below, synthesize a ?-ketoester, hydrolyze ester back to the carboxylic acid, and perform the decarboxylation. Ketone 1) CH
CH
O
2) H
Heat ?-ketoester H
H
O ?-ketocarboxylic acid<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The Correct Answer and Explanation is:<\/mark><\/strong><\/p>\n\n\n\n

Here are the completed chemical structures for the reaction sequence.<\/p>\n\n\n\n

Explanation<\/h3>\n\n\n\n

The reaction sequence outlines a method for synthesizing a ketone from an ester, involving three main steps: a Claisen condensation, ester hydrolysis, and decarboxylation.<\/p>\n\n\n\n

1. Synthesis of the \u03b2-ketoester:<\/strong> The first step is a Claisen condensation. Two molecules of the starting material, ethyl propanoate, react in the presence of a strong base, sodium ethoxide (CH3CH2O-). The ethoxide removes an acidic \u03b1-proton from one ester molecule to form a nucleophilic enolate. This enolate then attacks the electrophilic carbonyl carbon of a second ester molecule. The resulting tetrahedral intermediate collapses, eliminating an ethoxide ion to form the \u03b2-ketoester product, ethyl 2-methyl-3-oxopentanoate. An acidic workup (H+) is required in the second part of this step to neutralize the reaction mixture and protonate the enolate of the product, yielding the final neutral \u03b2-ketoester.<\/p>\n\n\n\n

2. Hydrolysis to a \u03b2-ketocarboxylic acid:<\/strong> The \u03b2-ketoester is then treated with acid (H+) and water. This is an acid-catalyzed ester hydrolysis reaction. The ethyl ester group (\u2013COOCH2CH3) is converted into a carboxylic acid group (\u2013COOH). This transformation yields 2-methyl-3-oxopentanoic acid, which is a \u03b2-ketocarboxylic acid because the ketone group is on the beta-carbon relative to the carboxyl group.<\/p>\n\n\n\n

3. Decarboxylation to a Ketone:<\/strong> The final step involves heating the \u03b2-ketocarboxylic acid. Molecules of this type are thermally unstable and readily undergo decarboxylation, which is the loss of a molecule of carbon dioxide (CO2). The reaction proceeds through a stable, cyclic six-membered transition state. This process results in the formation of an enol intermediate, which rapidly rearranges (tautomerizes) to the more stable final product, the ketone 3-pentanone. This overall sequence is a variation of the acetoacetic ester synthesis, a powerful method for preparing substituted ketones.<\/p>\n\n\n\n

\"\"<\/figure>\n","protected":false},"excerpt":{"rendered":"

Starting with the ester shown below, synthesize a ?-ketoester, hydrolyze ester back to the carboxylic acid, and perform the decarboxylation. Ketone 1) CHCHO2) HHeat ?-ketoester HHO ?-ketocarboxylic acid The Correct Answer and Explanation is: Here are the completed chemical structures for the reaction sequence. Explanation The reaction sequence outlines a method for synthesizing a ketone […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-241781","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/241781","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=241781"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/241781\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=241781"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=241781"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=241781"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}