Very low-pressure pyrolysis (VLPP) of 3-chloropropionitrile

Abstract

The thermal decomposition of 3-chloropropionitrile has been investigated over the temperature range 942–1152 K using the technique of very low-pressure pyrolysis (VLPP). The experimental results are consistent with the reaction proceeding via the unimolecular elimination of HCl CH₂ClCH₂CN → C₂H₃CN + HCl. The high-pressure Arrhenius parameters obtained via the application of RRKM theory are given by log (k_∞/s^–1)=(13.2 ± 0.3)–(241.0 ± 4 kJ mol^–1)/2.3 RT.

In contrast to its decomposition in a conventional static system, no radical reactions occur under VLPP conditions. No evidence could be found for the unimolecular elimination of HCN. When compared with the extant kinetic parameters for the unimolecular elimination of HCl from ethyl chloride, the results show that β-cyano substitution has a retarding effect on the rate of HCl elimination. This is consistent with a polar transition state.