Reactions of keten. Part IV. Kinetics and thermodynamics of the gas-phase reaction: thioacetic acid + keten ⇆ acetic thioanhydride

Abstract

The homogeneous gas-phase reaction CH₃COSH + CH₂:CO ⇆ Ac₂S has been studied in both directions over the temperature range 128–253°. The forward reaction is of the second order, k= 10^5·45 exp (–37,900/RT) l mol^–1 s^–1, and the back reaction first order, k= 10^11·02 exp (–131,000/RT) s^–1. Equilibrium constants were measured starting from both sides of the reaction, and calculated from the ratio of the rate constants. From the mean of these was obtained ΔH°=–94·7 kJ mol^–1 and ΔS°=–140·8 J K^–1 mol^–1. Results are compared with those obtained for the keten–acetic acid system.