Koch reaction carboxylic acid synthesis

H. Koch [593] formulated the mechanism of the carboxylic acid synthesis found by him via initial formation of a carbonium ion from the starting material and the acid catalyst with subsequent addition of carbon monoxide to the carbonium ion to give an acylium cation in the first reaction step (1) followed by the reaction of the acylium cation with water or alcohol in the second step (2). 

The Koch carboxylic acid synthesis proceeds with high reaction velocity if care is taken to stir the reaction mixture sufficiently. After formation of the acylium cations, the carboxylic acids can be separated nearly quantitatively by adding the stoichiometric amount of water if suitable catalysts are applied. Therefore in most cases solvents or dilution mediums are not required. 

The reaction is also called hydrocarboxylation. According to a later modification, the alkene first reacts with carbon monoxide in the presence of the acid to form an acyl cation, which then is hydrolyzed with water to give the carboxylic acid.97 The advantage of this two-step synthesis is that it requires only medium pressure (100 atm). Aqueous HF (85-95%) gave good results in the carboxylation of alkenes and cycloalkenes.98 Phosphoric acid is also effective in the carboxylation of terminal alkenes and isobutylene, but it causes substantial oligomerization as well.99 100 Neocarboxylic acids are manufactured industrially with this process (see Section 7.2.4). The addition may also be performed with formic acid as the source of CO (Koch-Haaf reaction).101 102 The mechanism involves carbocation formation via protonation of the alkene97 103 [Eq. (7.10)]. It then reacts with carbon monoxide... 

O. R. XVIII-I, M. J. Jorgenson, Preparation of Ketones from the Reaction of Organo-lithium Reagents with Carboxylic Acids XVI, A. J. Nielsen and W. J. Houlihan, The Aldol Condensation IV-5, W. S. Ide and J. S. Buck, The Synthesis of Benzoins II-3, T. A. Geissman, The Cannizzaro Reaction V-6, N. N. Crounse, The Gattermann-Koch Reaction I-10, F. f. 3licke, The Mannich Reaction. ... 

The carbonylation of olefins, by using such strong acids such as H2SO4, H3PO4-BF3, or HF-SbFs (superacids or magic acids) as catalysts, is known as the Koch synthesis. It 3delds predominantly branched isomers of carboxylic acids Neo acids (Exxon) and Versatic acids (Shell). The economic importance of these products is far less than that of the compovmds obtained by Reppe reactions (85,86). 

The isolation of saturated and unsaturated acetic acid derivatives in the manganese(m) acetate oxidation of olefins has been reported earlier examples of this oxidation led solely to y-lactones. A one-step synthesis of aeo-di-carboxylic acid diesters has been reported, based on Kolbe electrolysis of oxalic and malonic half-esters in the presence of olefins, and is exemplified in Scheme 2. As part of a study of insect hormone activity, Kolbe electrolysis has been utilized in the preparation of aj9-unsaturated Cj4—Cj7 acid esters with a terminal quaternary alkyl group. The utility of liquid hydrogen fluoride in the Koch carbonylation of olefins has been descried, as has a general study of this reaction. ... 

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