PURPOSE: To obtain a noncondensed polyaromatic compd. which is partially brominated exclusive of polyphenylene ether at a high selection rate by brominating the polyaromatic compd. in the presence of a zirconium halide catalyst at a specific temp. by using a specific amt. of bromine.

CONSTITUTION: The polyaromatic compd. like polyphenylene ether of formula ((n) is an integer from 1 to ≥20), such as diphenyl ether, is brought into reaction with the liquid bromine of 5 to 24 mol. for each of the respective equivalents of the polyaromatic compd. with the value obtd. by dividing the mol.wt. of the polyaromatic compd. by the number of benzene rings as the equivalent in the presence of the catalyst amt. of the zirconium halide catalyst, such as ZnCl4, in a substantially absent state of a solvent, by which the compd. is brominated, thereby the objective compd., such as brominated diphenyl ether, contg. average 6 pieces of Br per molecule useful as a fire retardant for org. substances, such as polyethylene, polyester, ABS and high-impact polystyrene, is obtd.