Radiation Chemistry of Dicarboxylic Acids in the Solid State. II. C-13 Isotope Effects in the Radiation-induced Decarboxylation of Malonic and Several Aliphatic Dicarboxylic Acids

Abstract The C-13 isotope effects in the radiation-induced decarboxylation of several dicarboxylic acids were investigated. Malonic acid showed a C-13 isotope effect of about 2%; this is much greater than those of monocarboxylic acids. The greater isotope effect of malonic acid is attributed to the intramolecular competition of the C-carboxyl bond rupture. Succinic, adipic, and pimeric acid, in which the intramolecular interaction of two carboxyl groups can be expected, gave large isotope-effect values, whereas glutaric and sebatic acid, in which such an effect may be expected to be small, showed lower isotope effects. Analogously, maleic acid (cis isomer) showed a larger isotope effect than did fumaric acid (trans isomer).