Boron triiodide

Boron triiodide

Boron triiodide is a chemical compound with the formula BI₃. It is one of the most important boron halides, alongside boron trifluoride (BF₃), boron trichloride (BCl₃), and boron tribromide (BBr₃). Boron triiodide is used in organic synthesis as a strong Lewis acid to catalyze reactions such as Friedel-Crafts acylations and as a reagent in the preparation of organoiodine compounds.

Properties

Boron triiodide is a colorless, crystalline solid at room temperature, with a sharp, pungent odor. It is highly reactive, especially with water, releasing hydrogen iodide gas. Due to its high reactivity, it must be handled with care, under strict safety protocols to avoid moisture and air exposure. It has a melting point of 49.9°C and a boiling point of 210°C.

Synthesis

Boron triiodide can be synthesized by the direct combination of elemental boron and iodine at elevated temperatures. Alternatively, it can be produced by the reaction of boron with iodine monochloride (ICl) in the presence of aluminum trichloride (AlCl₃) as a catalyst.

Applications

In organic chemistry, boron triiodide is utilized as a powerful Lewis acid catalyst in various chemical reactions, including the Friedel-Crafts reaction, where it facilitates the alkylation and acylation of aromatic compounds. It is also used in the synthesis of alkyl iodides and vinyl iodides, serving as a source of iodine in these reactions.

Safety

Boron triiodide is highly corrosive and poses significant risks upon exposure. It can cause severe burns to the skin and eyes and is harmful if inhaled or ingested. Proper safety equipment, including gloves, goggles, and fume hoods, must be used when handling this compound. It is also important to store it in tightly sealed containers under an inert atmosphere to prevent decomposition and reaction with moisture in the air.