The chlorination of isophthaloyl and terephthaloyl chloride in the presence of iron leads to 5- chloroisophthaloyl chloride and 2, 3, 5, 6-tetrachloroterephthaloyl chloride, respectively. The latter compound, due to its highly hindered structure, shows considerable stability toward reagents which are capable of attacking an acid chloride. The chlorinated phthaloyl chlorides have been converted to a number of derivatives.
