Free‐radical chain dechlorination of chloroethanes in liquid triethylsilane

The kinetics and mechanism of the free‐radical chain dechlorination of C 2 Cl 6 , C 2 Cl 5 H, and sym ‐C 2 Cl 4 H 2 in Et 3 SiH wereinvestigated over a wide temperature range. The propagation step of the dechlorination of chloroethanes (C 2 Cl x H 6− x ) proceeds by the following reactions:Analysis of the temperature dependence of product formation gave the Arrhenius expressions for k 4 / k 3 which in turn were utilized for the estimation of the absolute Arrhenius parameters for hydrogen abstraction from Et 3 SiH. Our results show that the values of E abs are lower in Et 3 SiH than in c ‐C 6 H 12 by about 2–3 kcal/mol, while the A factors are almost equal. In competitive studies k 2 was determined versus Br abstraction from n ‐C 5 H 11 Br. The relative Arrhenius parameters determined by this method show that variations in both A factors and activationenergies are responsible for the reactivity trends observed in the Cl transfer reactions of Et 3 Si radicals.