Acrylic acid is the simplest unsaturated carboxylic acid, and its molecular structure consists of a vinyl group and a carboxyl group. Pure acrylic acid is a colorless, clear liquid with a characteristic pungent odor. Density 1.0511. Melting point 14°C. Boiling point 140.9°C. Strong acidity. Corrosive. Soluble in water, ethanol and ether. Chemically active. Easy to polymerize to form a transparent white powder. Propionic acid is generated when reduced. 2-chloropropionic acid is generated when hydrochloric acid is added, which is used to prepare acrylic resins, etc., and is also used in other organic syntheses. It is obtained by oxidation of acrolein or hydrolysis of acrylonitrile, and can also be synthesized from acetylene, carbon monoxide and water, or by pressurized oxidation of ethylene and carbon monoxide.