Boron tribromide

Boron tribromide, BBr3, is a liquid compound containing boron and bromine. It is usually made by heating boron oxide with carbon in the presence of bromine: this generates free boron which reacts vigorously with the bromine. It is very volatile and fumes in air because it reacts vigorously with water to form boric acid and hydrogen bromide.

This compound is commercially available and acts as a strong Lewis acid. Boron Tribromide is an excellent demethylating or dealkylating agent for ethers, often in the production of pharmaceuticals. Additionally, it also finds applications in olefin polymerization and in Friedel-Crafts chemistry as a Lewis acid catalyst. The electronics industry uses boron tribromide as a boron source in pre-deposition processes for doping in the manufacture of semiconductors.

Synthesis
The reaction of boron carbide with bromine at temperatures above 300°C leads to the formation of boron tribromide. The product can be purified by vacuum distillation.