Kinetic Carbon Isotope Effects in the Decarbonylation of Lactic Acid of Natural Isotopic Composition and of [1-14C] Lactic Acid

Abstract

Abstract Studies of carbon-13 and carbon-14 kinetic isotope effects (K. I. E.) in the decarbonylation of lactic acid (L. A.) in sulphuric acid and in phosphoric acids media have been summarized and compared with earlier studies of 14C and 13C K. I. E. in the decarbonylation of formic and oxalic acids in concentrated sulphuric acid. Supplementary data concerning the decarbonylation of L. A. in sulphuric acid diluted with water and in pyrophosphoric acid are presented and discussed. The observed temperature dependences of 13C and 14C K. I. E. in concentrated H2SO4 and in concentrated phosphoric acids media have been rationalized by invoking a change of the mechanism of decarbonylation of L. A. in concentrated sulphuric and phosphoric acids with temperature. Preliminary calculational results concerning 13C and 1∗∗C K. I. E. in decarbonylation processes are also presented. In H2SO4 diluted with water and in H3PO4 diluted with water the temperature dependence of 13C and 14C K. I. E. is normal and well reproduc...