These halogen-containing ethylbenzene derivatives may be prepared by reacting a vinyl compound such as acrylonitrile, acrylic acid, an acrylate or an amide with abenzenediazonium salt and halogen ions.Heretofore, in this method (i.e. a method using a so-called Meerwein reaction), it has been most common to conduct the reaction by using a copper compound catalyst in a solvent mixture comprising ace