BCl3

Boron trichloride (BCl3) is an inorganic compound with the formula BCl3. It is a colorless, highly volatile gas that fumes in air and has a boiling point around -12 °C, readily condensing to a liquid at lower temperatures. It is extremely reactive and moisture sensitive, and exposure can be corrosive and harmful.

The molecule is trigonal planar at boron, reflecting its electron deficiency and status as a strong Lewis acid. BCl3 accepts electron pairs from bases to form adducts such as BCl3·ether or BCl3·amines. In the absence of strong donors, BCl3 tends to associate into B2Cl6 via bridging chlorides, particularly in the gas phase.

BCl3 hydrolyzes readily in water: BCl3 + 3 H2O → B(OH)3 + 3 HCl. It also reacts with alcohols and other oxygen- or nitrogen-containing donors to form boron esters or adducts. As a Lewis acid, it participates in various organic transformations, often as a reactive intermediate or catalyst, and is used in the synthesis of boron-containing compounds.

Industrial production is typically achieved by chlorinating boron-containing materials, such as B2O3, with chlorine or hydrogen chloride at elevated temperature: B2O3 + 6 HCl → 2 BCl3 + 3 H2O. BCl3 is handled under strictly dry, inert conditions to prevent hydrolysis and corrosion.

Safety: BCl3 is highly corrosive and toxic; it reacts violently with water, releasing HCl gas. It should be handled with appropriate protective equipment and in well-ventilated, dry systems.