Carbon-14 kinetic isotope effect in the decarbonylation of lactic acid[1-14C]

The carbon-14 kinetic isotope effect for the decarbonylation of lactic acid1-¹⁴C] in sulfuric acid has been measured in the temperature interval of 20–90°C. The experimental values of (k_12C/k_14C) are compared with the theoretical¹⁴C kinetic isotope effect calculated assuming that one carbon-oxygen stretching vibration is lost in the rate-determining step. The discrepancy between experimentally observed temperature dependence of the¹⁴C kinetic isotope effect and the theoretical one is explained by the possible side reactions which change the apparent degrees of decarbonylation and isotopic composition of CH₃CHOHCOOH1-¹⁴C] used in experiments aiming at the determination of carbon-14 kinetic isotope effect in the decarbonylation process itself.