Demethylation of Carcinogenic Aminoazo Dyes by Autoxidizing Linoleic Acid.

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Abstract
P-Dimethylaminoazobenzene and p-monomethylaminoazobenzene both increased the latent period of autoxidation of linoleic acid, the former being a more effective antioxidant than the latter. The antioxidant effect of each dye was proportional to the concn. employed. Other dyes with approx. the same inhibiting effect as p-dimethylamino-azobenzene were [image]''-methyl-g-dimethylaminoazobenzene, P''-methyl-p-dimethylaminoazobenzene, and p-ethylmethylamino-azobenzene. In contrast p-diethylaminoazobenzene had only a slight effect and p-aminoazobenzene had no inhibitory influence. During the latent period, an output of gas was observed when any of the methylated dyes were mixed with the linoleic acid; a gas output was also found with autoxidizing linoleic acid alone at the end of the oxidation period. The gas evolved was probably CO2. As autoxidation of the linoleic acid-dye mixtures proceeded demethylation of p-dimethylaminoazo-benzene and p-monomethylaminoazobenzene occurred. At the end of 30 hrs., 90% of the p-dimethylaminoazobenzene initially added had disappeared and as much as 85% was accounted for in the form of the monomethyl derivative. Thereafter, the amt. of p-monomethylaminoazobenzene decreased. Small amts. of -aminoazobenzene also were formed. The demethylation occurred only during autoxidation; none was found when the oxidation was inhibited with tocopherol.