Sensitivity to polar effects of reactions of homolytic substitution with cleavage of the C-Br bond and chain transfer constants in the radical telomerization of vinyl chloride with CBrCl3

Abstract

1. The particular transfer constants were determined for radicals with a chain length from one to three monomer units in the radical telomerization of vinyl chloride with CBrCl3 at 55, 105, and 145°. 2. The polar properties of the reagents (estimated using the Bamford correlation equation) significantly influence the rate of homolytic reactions of substitution at the C-Br bond (in CBrCl3), and the sensitivity to polar effects is close to substitution at the C-Cl bond (in polychloromethanes) and substantially higher than in the case of cleavage of the C-H bond (in chloroform). 3. It was hypothesized that this is due to the higher degree of cleavage in the transition state of the weaker C-halogen bond and an increase in the probability of electron transfer or the role of ionic structures in the decrease in the activation energies of the corresponding substitution reactions.