CARBON-ISOTOPE EFFECT STUDIES IN THE MECHANISM OF REACTIONS OF ALKYNES WITH FORMIC-ACID - II - C-13 FRACTIONATION IN THE DECARBONYLATION OFMERCK FORMIC-ACID IN THE PRESENCE OF PHENYLACETYLENE

The C-13 fractionation has been studied in the reaction of phenylacety lene with the excess of liquid Merck formic acid at 30 and 40 degrees C to see the contribution of the C-13 fractionation in the formolysis of transient alpha-formoxystyrene to the experimentally observed globa l C-13 fractionation. The C-13 fractionation has been investigated als o in the hydration of 1 ml of PhC = CH with 1 ml of formic acid in the temperature interval of 80-100 degrees C. The C-13 KIE equal to 1.016 8 at 91.75 degrees C and 1.0167 at 100 degrees C indicate that the sel f-decomposition of formic acid in such experimental conditions is alre ady largely suppressed. The isotope effect is discussed within the fra mework of the sequence of reaction steps leading to acetophenone and c arbon monoxide production listed in part I.