The addition of bromine to phenylpropiolic acid

Abstract

During recent years, much work has been done on the addition of bromine to olefinic substances (see especially (1) Robertson, Clare, McNaught and Paul). Comparatively little work, however, has been attempted on acetylenic substances, and the object of the present research has been to study the reaction between bromine and a simple acetylenic acid, phenylpropiolic acid. It is known that in general bromine addition takes place by the effective impact of the positively-charged atom of the polarised bromine atom upon the negatively-charged atom of the unsaturated system (Lowry 5) and the subsequent coupling of the positively-charged atom of the unsaturated system with the negative bromine ion. The latter has a separate if momentary existence, which is aided by an ionising solvent, and if the solvent is itself ionised, the negative ions of the solvent may compete with the bromine for addition to the unsaturated system (Read and Read 2). It has been shown in the work of Robertson and co-workers (1) already mentioned that for olefinic substances in solution there are three main types of reaction possible. These are - (1) unimolecular surface reactions, being heterogeneous, (2) homogeneous bimolecular reactions, (3) homogeneous termolecular reactions.