AbstractBenzyl chloride has been used in a kinetic study of chlorine replacement by acetoxy groups to model the behaviour of allylic chlorine during the acetoxylation of poly(vinyl chloride). Chlorine substitution was carried out in tetrahydrofuran at 30°C using a potassium acetate‐crown ether complex with methanol to ensure homogeneous solution. The process followed an SN2 mechanism. The orders of reaction with respect to benzyl chloride and potassium acetate were close to one, and the second order velocity constant was 4.2 x 10−5litre mol−1s−1when the molar ratio of crown ether to potassium acetate was approximately unity. Higher ratios caused a slight increase in rate constant. Substitution was followed by NMR spectroscopy which also revealed a proton exchange between methanol and acetate anion with an equilibrium constant 9.4 x 10−2. This observation has suggested an explanation for the effect of some free‐radical inhibitors on the rate of acetoxylation of poly(vinyl chloride) by potassium acetate in the presence of