[{"from": "human", "value": "Provide a brief overview of this molecule. [C][C][=Branch1][C][=O][C][Br]"}, {"from": "gpt", "value": "The molecule appears as a clear colorless liquid turning violet on standing, even in the absence of air, and decomposing to a black resinous mass on long standing. Denser than water and poorly soluble in water. Hence sinks in water. A violent lachrymator--low concentrations are very irritating to the eyes; high concentrations or prolonged exposure at lower concentrations may have adverse health effects. Very toxic by inhalation. Contact with the liquid causes painful burns. Used as a chemical war gas."}]