AsCl3

AsCl3, or arsenic trichloride, is an inorganic compound with the formula AsCl3. It contains arsenic in the +3 oxidation state and behaves as a covalent, reactive substance that is volatile and can fume in air. It hydrolyzes readily in water and moisture to give arsenous acid (H3AsO3) and hydrogen chloride (HCl).

Preparation and structure: AsCl3 is produced industrially by chlorinating arsenic trioxide or directly from arsenic metal. A common route is As2O3 + 6 HCl → 2 AsCl3 + 3 H2O, while direct chlorination can be described by 2 As + 3 Cl2 → 2 AsCl3. In solution, AsCl3 acts as a Lewis acid and readily forms adducts with bases such as ethers and amines.

Reactivity and use: Arsenic trichloride reacts with water and oxygen-containing substances, producing HCl and arsenous acid. It forms a range of arsenic-containing derivatives upon reaction with alcohols, amines, and other nucleophiles, and is used as a precursor in the synthesis of organoarsenic compounds. Historically, it has been employed in organic synthesis and in the production of certain arsenic-containing materials; however, its toxicity has limited its modern use.

Hazards and handling: AsCl3 is highly toxic and corrosive. Exposure can cause severe irritation, damage to the eyes and skin, and systemic effects with prolonged or high-level exposure. It hydrolyzes to release corrosive HCl and arsenous acid. It should be handled only under a properly functioning fume hood with appropriate personal protective equipment, and kept away from moisture and incompatible materials. Waste and spills are managed as hazardous chemical waste, with attention to environmental toxicity.