Constitutional effects on the addition of halogens to substituted cinnamic acids

Abstract

The addition of a halogen molecule to an unsaturated compound is not the simple process that it would appear to be, but rather a complex mechanism. The rate at which the addition takes place is determined by many factors, among the most important of which are, the environment of the unsaturated link, the nature of the solvent in which the reaction is carried out, temperature, concentration etc. The early investigators were limited to a comparison of the rates of Bromine addition to various substituted ethylenes in Carbon-tetrachloride and these results were classified as rapid, slow and of very slow reactivity. Francis (1) revealed the mechanism of the process when he discovered that, on bromination in aqueous solution, a foreign ion could replace a bromine atom in the addition process. For example, in the bromination of ethylene in water containing excess chloride ions, a chloro-bromo derivative is formed.