Studies Involving Isotopically Labeled Formic Acid and its Derivatives.1,2 V. Studies of the Decarbonylation of Formic, Benzoylformic and Triphenylacetic Acids in Sulfuric Acid

Abstract

By employing deuterium and carbon-14 isotope fractionation studies, carbon-14 tracer studies, and oxygen-18 isotope exchange studies, definite irformation was obtained about the mechanism of decarbonylation of formic acid, triphenylacetic acid and benzoylformic acid in concentrated sulfuric acid. The experimental results are in accord with previously proposed mechanisms of decarbonylation of formic and benzoylformic acids. In the case of the triphenylacetic acid decarbenylation, strong evidence is presented that a previously proposed mechanism is incorrect. A tentative mechanism for the decarbonylation of triphenylacetic acid which will account for the experimental observations was suggested. An oxygen-18 exchange between carbon monoxide and concentrated sulfuric acid was observed. A general discussion of isotopic methods which are applicable to the study of decarbonylation reactions and other similar reactions is included. Specific activity-per cent reaction curves that facilitate rapid computation of kinetic isotope effects are presented. (auth)