ISOTOPE EFFECTS IN CHEMICAL REACTIONS

Abstract

The effect on reaction rates caused by substitution of C-3 for C12 has been measured for two organic decomposition reactions. Isotope effects have been found in the thermal decarboxylation of malonic acid and in the decomposition of oxalic acid in concentrated sulfuric acid. Ealonic and oxalic acid molecules containing only C^2 carbon atoms -..-ere found to decarboxylate about 3.5% faster than those containing a 0^° isotope in a carboxyl position. It was found that C^3 did not distribute itself equally among the decomposition products of oxalic acid, but showed a 3.3% preference for the carbon dioxide rather than carbon monoxide. A 2.1% greater probability of rupture of C-l-2-C-i-2 over c^-C-3 bonds in the decarboxylation of malonic acid was observed. The effect of temperature on the isotope effects in malonic acid was investigated. The magnitude of the effects was found to be constant in the temperature range studied.