Polar Radicals. VIII. Kinetic Studies on the Mechanism of the Vapor Phase Bromination of 1-Chlorobutane. The Role of Reversible Hydrogen Abstraction

A general method for the evaluation of the kinetics of the vapor phase brominations of alkanes and substituted alkanes is presented. The method is applied to the bromination of 1-chlrobutane.The hydrogen abstraction reaction and its reversal are both found to be deactivated by the polar influence of the substituent; the effect, as predicted, falls off as the distance of the substituent from the C—H bond involved increases. In the vapor phase bromination of 1-chlorobutane, because of this deactivated reversal, transfer with hydrogen bromide cannot compete (< 10%) with transfer with molecular bromine.There was no evidence for anchimeric assistance by the neighboring chlorine atom during hydrogen abstraction.