Presence of 3 : 4–8 : 9-Dibenzpyrene in Coal-Tar

Abstract

ALTHOUGH several carcinogenic hydrocarbons of varied potency have been isolated from coal-tar, including 1 : 2–5: 6-dibenzanthracene, 3 : 4-benzpyrene¹, and 1 : 12-benzperylene², it is known that the presence of such substances is not sufficient to account for both the qualitative and the quantitative carcinogenicity of coal-tar itself. This consideration warranted the search for further carcinogens in coal-tar, particularly in pitch fractions containing the more condensed aromatic hydrocarbons, and especially in view of the considerable carcinogenic activity of several hexacyclic hydrocarbons such as 3 : 4–8 : 9-(I)³ and 3 : 4–9: 10-dibenzpyrene (II)⁴. Schoental⁵ has recently reported the presence of (II) in a carcinogenic fraction of coal-tar, and this prompted the present report of the isolation of another potent carcinogen, 3 : 4–8 : 9-dibenzpyrene, from similar material. This hydrocarbon, which was isolated in small amounts by the usual fractionation and chromatographic methods, from the fractions boiling above 500° C. of various samples of coal-tar pitch, was identified by direct comparison of melting point and ultra-violet and fluorescence spectra with those of an authentic sample prepared by zinc dust reduction of 3 : 4–8 : 9-dibenzpyrene-5 : 10-quinone⁶.