Kinetics of the competitive elimination of hydrogen chloride and hydrogen fluoride from chemically activated 1,1,1-difluorochloroethane from ketone photolysis

Abstract

The rates of elimination of hydrogen chloride and hydrogen fluoride have been compared with the rates of stabilization by collision for chemically activated 1,1,1-difluorochloroethane over a range of pressure and temperature. The energized molecules have been produced by radical combination from the co-photolysis of acetone and 1,3-dichloro-1,1,3,3-tetrafluoroacetone mixtures. The ratios of k(elimination of hydrogen fluoride)/k(deactivation by collision) and k(elimination of hydrogen chloride)/k(deactivation by collision) at room temperature are 0·4 and 0·1 cm. respectively.

The classical Rice–Ramsperger–Kassel theory of unimolecular reactions is shown to give a quantitative description of the competitive decomposition of the excited molecules. Reasonable values of the critical energy necessary for decomposition are CH₃CF₂Cl → CH₂CF₂+ HCl (58 kcal. mole^–1) and CH₃CF₂Cl → CH₂CFCl + HF (56–57 kcal. mole^–1).