Higher brominated pyrene prepn. - by reacting pyrene-contg. coal tar fraction with chlorine and bromine at room temp. in soln

Higher brominated pyrenes, (I) are prepd. by letting 4.4g atom Br2 and 4.4 g atom Cl2 act simultaneously, at 20-30 degrees C, in a solvent, on 1 mol pyrene present in a pyrene fraction recovered by coal tar distn. Prod. contains 90% 3,5,8-tribromo-pyrene and 10% dichloropyrene and can be oxidised to naphthalene-1,4,5,8-tetracarboxylic acid, (II), known as a dyestuff precursor. Yields of (II) correspond to those obtd. from 3,5,8,10-tetrabromo-pyrene prepd. by the technically more difficult bromination of pure pyrene. In reaction, Br2 is used to substitute the aromatic hydrocarbon, while Cl2 bonds H released to HCl.