PURPOSE: To obtain the compd. of the purpose with industrially high productivity, high yield and high purity by using a specified compd. as a desorbing agent and carrying out Hofmann elimination of a p-methylbenzyltrimethylamonium deriv. in an alkali soln.

CONSTITUTION: A p-methylbenzyltrimethylammonium deriv. expressed by formula I is subjected to Hofmann elimination at 50 to 150°C for 1 to 50 hours in an alkali soln. by using a compd. expressed by formula II such as hydroquinone, o-aminophenol and p-phenylene diamine in at least a catalytic amt. as an eliminating agent to obtain the compd. of the purpose expressed by formula III which is useful as an intermediate for the production of polyparaxylene. In formula I, B is halogen, alkyl, aralkyl, haloaralkyl (up to 20C); (p) is 0 to 4; Y is OH, halogen. In formula II, A is an aromatic group; X is an electron donating group; R is H, 1 to 4C alkyl; (n) is 1 to 6; (m) is 0 or 1 to such an integer number that m+n ranges the possible numbers of positions for substitution of the aromatic group A.