Photochlorination studies. Part 9.—1, 1-dichloroethylene

Abstract

The photochlorination of 1,1-dichloroethylene (vinylidene chloride) has been studied in a static system between 25 and 48°C using either continuous or intermittent illumination. The reaction follows a chain mechanism, similar to that established for other chloroalkenes, in which chain termination is by bimolecular association of trichloroethyl radicals at olefin pressures greater than 2 mm. The rate constants for recombination of C₂H₂Cl radicals (k₄) and for reaction with chlorine molecules (k₃) are given by log₁₀k₄(l. mole^–1 sec^–1)=(10.02±0.06)–(1.2±0.7 kcal mole^–1)/RT, log₁₀k₃(l. mole^–1 sec^–1)=(8.84±0.4)–(4.1±0.7 kcal mole^–1)/RT. The Arrhenius parameters for reactions in the photochlorination of all the chloroalkenes (C₂H₄Cl_4–n, 0⩽n⩽4) are summarized and discussed.