Bromine and chlorine, for instance, add readily to yield 1,2-dihaloalkanes. More than 6 million tons of 1,2-dichloroethane(also called ethylene dichloride) are syn- thesized each year in the United States by addition of Cl2 to ethylene. The product is used both as a solvent and as a starting material for the synthesis of poly(vinyl chloride), PVO.