t-butanol containing potassium t-butoxide and in ethanol containing sodiumethoxide. The rates of the E2 reaction of the sulphur compounds are found to be 102–103 times as great as those of the corresponding oxygen analogues in both media. These rates can be correlated with Hammett σ values. The ρ values obtained for sulphur compounds are 1·98 and 2·14 in t-butanol and ethanol, while those for oxygen