PURPOSE: To obtain mixed dimers free of α-halogen with different structures by the combination of three kinds of compounds by bringing a mixture of three kinds of halogenated p-methylbenzylmethylammonium compounds into Hofmann elimination reaction.

CONSTITUTION: Halogenated p-methylbenzyltrimethylammonium of formula I, a monohalobenzyl body of formula II and a dihalobenzyl body of formula III are selected so as to impart a prescribed distribution and are formed into a mixture, this mixture is reacted with an alkaline hydroxide, and Hofmann elimination reaction is allowed to occur to obtain a mixture of dimers with different structures of the formulae A to F. From this mixture, a parylene film and coating imparted with preferable characteristics can be obtd. They are particularly suitable for use in the electronics industry. Furthermore, at the time of executing the reaction, dimethylsulfoxide and at least one kind of reaction promoters (such as methylmethoxyethyl ether, crown ether, alkyl- substituted imidazolidinone or the like) are preferably present.