A kinetic study of the copper chloride-catalysed addition of benzenesulphonyl chloride to a number of styrenes carrying substituents of widely different electronegativity shows that the overall rates are very little affected by the substituent. This rules out the possibility of a concerted reaction, in which the olefin should participate in the rate-determining step, and confirms a redox chain mechanism. The lack of stereospecificity of the addition of carbon tetrachloride to norbornene points to the same conclusion. P-Methylstyrene reacts much more slowly with benzenesulphonyl chloride than the other styrenes. This is attributed to an unfavourable equilibrium for sulphonyl radical addition to this olefin. Carbon tetrachloride adds a t the same rate to different olefins, including P-methylstyrene, in accord with the redox chain mechanism.

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