Interaction of alcohols with hydrogen halides

Abstract

Abstract Previous and submitted evidence on the mechanism of interaction between an alcohol and a hydrogen halide points to the conclusion that the formation of an alkyl halide entails two steps: the rapid formation of an oxonium halide, ROH 2 + X − , and the rate‐determining dehydration of it. Results from the studies of kinetics and optical rotatory power are as yet inconclusive on the mechanism of the second step, but they point to the concurrence of several modes. The maximum amount of hydrogen halide absorbed by an alcohol depends on the nature of the alcohol and on the temperature. This amount is of great significance because it determines the maximum concentration of the oxonium halide, and also can control the extent to which the water produced reduces the rate of formation of alkyl halide. Because of these points, and because the concentration of halide ion can be increased, certain added substances, such as pyridine, dioxan and even water, can increase the rate of formation and final yield of alkyl halide. Results of experiments on the solubility of hydrogen chloride in different alcohols, and on the extraction of the halide by water, are discussed.