Hydrogen-deuterium isotope effect in the λ-initiated chain reaction between carbon tetrachloride and cyclohexane in the liquid phase

Abstract

The hydrogen-deuterium kinetic isotope effect for the chain reaction between carbon-tetrachloride and cyclohexane was measured in the liquid phase, in the temperature range from 302 to 413 K. The rate expression for the two following reactions was obtained by competitive experiments in ternary solutions of CCl 4 in c- C 6 H 12/ c- C 6 D 12 mixtures (2) ·CCl 3+c-C 6H 12→CHCl 3+c-C 6H 11 . (2′) ·CCl 3+ c-C 6D 12→CDCl 3+c-C 6D 11 . log 10 ( k 2/ k 2′)=-0.38±0.04-(10.1±0.3) kJ· mol -1/2.303 RT. The high value for the difference in activation energies between (2) and (2′) suggests that tunneling is important in the proton abstraction reaction by ·CCl 3.