Introduction to the Mechanism of the Hydrochlorination of Rubber

Abstract

Abstract The mechanism of rubber hydrochlorination is discussed in the light of the known crystal structure of rubber hydrochloride. The coiling of a rubber chain segment into a trans-decalin-shaped transition state is shown to be necessary and sufficient to explain the alternation along the polymer chain of d- and l-asymmetric carbon atoms, each separated from the next by three CH2 groups. As a preliminary to kinetic analysis, techniques are described for precise measurements of the degree of hydrochlorination of latex at various times of reaction. An analytical technique defines the reaction progress to 0.5 per cent, and serves to calibrate a diffusion-gradient method of following the reaction by density change. This method is at least equally sensitive, but more convenient. Despite the complexity of the natural-latex medium, the reaction kinetics are shown to be reproducible and free from uncontrolled effects. The reaction is rate-controlled chemically rather than by transport. The main part of the rate curve consists of two straight-line (zero-order) portions meeting at a kink.