Pyrolysis of thiocyanates and isothiocyanates. Part IV. Effect of structure on thiocyanate elimination

Abstract

The mechanistic study of the pyrolysis of thiocyanates has been continued with the detailed kinetic investigation of the gas-phase elimination of isopropyl, t-butyl, and but-3-enyl thiocyanates for which the Arrhenius equations are: k₁= 10^12·27 exp (–39,330/RT) s^–1, k₁= 10^12·28 exp (–37,370/RT) s^–1, and k₁– 10^12·34 exp (–41,879/RT) s^–1 respectively. Rate data at one temperature were also obtained for n-propyl and 2-phenylethyl thiocyanates. The structure and character of the transition state for this reaction, which is believed to be homogeneous and unimolecular, is discussed and a six-centre concerted mechanism is suggested.