The addition of chloroform to alkenes to give 1 : 1 adducts has been studied at 60-160 °C. In the addition to styrene taken as a model reaction, copper complexes formed from metallic copper or cuprous oxide and 1,10-phenanthroline showed highest catalytic activity and selectivity even under mild conditions and gave 1,1,3-trichloro-3-phenylpropane in up to 95% yields. Aliphatic alkenes and vinyl monomers were less reactive than styrene. The mechanism proposed for redox chain additions of chloroform involves chain transfer via copper complexes.