Halogen Exchange in Near-Critical Water

Abstract

Bromoaromatics are ubiquitous in chemistry, and their manufacture is often wasteful. Halogen exchange under hydrothermal conditions constitutes a viable alternative for their synthesis in some cases. The prepara-tion of 1,2-dibromobenzene and 1-bromo-2-chlorobenzene from 1,2-dichlorobenzene, by treatment with hy-drobromic acid in hydrothermal media at temperatures ranging from 240?C to 320?C was investigated as a viable alternative to de novo synthesis. The effects of temperature, exchange duration and the presence of Fe3+ salts on product yields are discussed. Yields for both targeted haloarenes of up to 37% and 48%, respec-tively, were achieved, with very limited formation of 1,3- and 1,4-dihalobenzene isomers. A mechanism for halogen exchange was proposed.