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Ketonic decarboxylation (also known as ketonization) is a type of organic reaction and a decarboxylation converting two equivalents of a carboxylic acid to a symmetric ketone by the application of heat with expulsion of one equivalent of water and one equivalent of carbon dioxide. Bases promote this reaction. The reaction mechanism likely involves nucleophilic attack of the alpha-carbon of one acid group on the other acid group's carbonyl, possibly as a concerted reaction with the decarboxylation. The initial formation of an intermediate carbanion with decarboxylation from one acid group prior to the nucleophilic attack has been proposed, but is unlikely since the byproduct resulting from the carbanion's protonation by the acid has never been reported. This reaction is different from oxidative decarboxylation with proceeds through a radical mechanism and is characterised by a different product distribution in isotopic labeling experiments with two different carboxylic acids. With two different carboxylic acids the reaction behaves poorly because of poor selectivity except when one of the acids (small, volatile) is used in large excess. ==Examples== The dry distillation of calcium acetate to acetone was reported by Charles Friedel in 1858 〔Friedel, C. (1858), Ueber s. g. gemischte Acetone. Justus Liebigs Ann. Chem., 108: 122–125. 〕 and until World War I ketonization was the premier commercial method for its production.〔''IMPROVEMENT IN THE MANUFACTURE OF ACETONE.1'' E. R. Squibb Journal of the American Chemical Society 1895 17 (3), 187-201 〕 Ketonic decarboxylation of propanoic acid over a manganese(II) oxide catalyst in a tube furnace. affords the synthesis of 3-pentanone. Of commercial importance is the production of 3-pentanone from propionic acid with catalysts cerium(IV) oxide and manganese dioxide on alumina. An example of intramolecular ketonization is the conversion of adipic acid to cyclopentanone with barium hydroxide.〔.〕 : 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ketonic decarboxylation」の詳細全文を読む スポンサード リンク
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