bromobenzenes

Bromobenzenes are aryl bromides in which one or more hydrogen atoms on the benzene ring are replaced by bromine. The simplest member is bromobenzene (C6H5Br), a colorless liquid with a characteristic odor and a boiling point around 156 °C. The term also covers higher brominated derivatives, including the dibromobenzenes: 1,2-dibromobenzene (o-), 1,3-dibromobenzene (m-), and 1,4-dibromobenzene (p-). In typical preparations, bromination of benzene affords bromobenzene, which can be further brominated to give the di‑ and polybrominated benzenes; the existing bromine substituent directs electrophilic bromination to the ortho and para positions, yielding mainly the 1,2- and 1,4- dibromobenzenes with the meta isomer usually less prominent.

Industrial production generally involves bromination of benzene using bromine in the presence of a Lewis acid catalyst such as ferric bromide (FeBr3). Alternative routes include bromination of prefunctionalized or partially brominated benzenes and stepwise substitution strategies to obtain desired substitution patterns.

As aryl halides, bromobenzenes are valuable intermediates in organic synthesis. The carbon–bromine bond is a reactive leaving group, making bromobenzenes suitable substrates for palladium-catalyzed cross-coupling reactions (such as Suzuki–Miyaura and Heck couplings) to form biaryl and other aryl-aryl linkages. They are also involved in various nucleophilic substitutions and other transformations, though their reactivity differs from that of chloro- or iodobenzenes.

Safety considerations are important: bromobenzenes and many of their derivatives are toxic and may pose environmental and health risks, requiring appropriate handling, containment, and disposal.