an aldehyde used as a starting material in the synthesis of 1-butanol (n-butyl alcohol), ethyl acetate, perfumes, flavourings, aniline dyes, plastics, synthetic rubber, and other chemical compounds. It has been manufactured by the hydration of acetylene and by the oxidation of ethanol (ethyl alcohol). Today the dominant process for the manufacture of acetaldehyde is the Wacker process, developed between 1957 and 1959, which catalyzes the oxidation of ethylene to acetaldehyde. The catalyst is a two-component system consisting of palladium chloride, PdCl2, and copper chloride, CuCl2.