Kinetics and mechanism of the gas phase photochlorination of 1,2-dichloro-1,2-difluoroethylene

Abstract

The gas phase photochlorination of 1,2-dichloro-1,2-difluoroethylene was studied in a static system at temperatures between 30 and 90°C. The rate was measured under both continuous and intermittent light of wavelength 436 nm. The only final product, CFCl₂,CFCl₂, is formed according to the equation + $\text{d[C}{}_2\text{F}{}_2\text{Cl}{}_4\text{]}\text{d}\text{t}$=k[Cl₂]J_abs^{$\text{1}\text{2}$} where J is the intensity of the absorbed light.

The rate constants determined under continuous illumination are as follows: k_30°C=5.63 ± 0.09 1^{$\text{1}\text{2}$} mol^{−$\text{1}\text{2}$} s^{−$\text{1}\text{2}$}, k_60°C = 10.43 ± 0.02 1^{$\text{1}\text{2}$} mol^{−$\text{1}\text{2}$} s^{−$\text{1}\text{2}$} and k_90°C = 21.26 ± 1.4 l^{$\text{1}\text{2}$} mol^{−$\text{1}\text{2}$} s^{−$\text{1}\text{2}$}.

The rate constants for the elementary reactions CFCl₂ĊFCl+Cl₂→C₂F₂Cl₄+Cl and 2CFCl₂ĊFCl→products are log k₃=8.68-$\text{4810±300 4.57}\text{T}$ and log k₄=8.91±0.21 respectively, where k₃ and k₄ are in litres per mole per second.