Abstract
Summary
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 concentration employed. Other dyes with approximately the same inhibiting effect as p-dimethylaminoazobenzene were m'-methyl-p-dimethylaminoazobenzene, p'-methyl-p-di-methylaminoazobenzene, and p-ethylmethyl-aminoazobenzene. In contrast p-diethyl-aminoazobenzene 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 carbon dioxide.
As autoxidation of the linoleic acid-dye mixtures proceeded demethylation of p-dimethylaminoazobenzene and p-monomethyl-aminoazobenzene occurred. At the end of 30 hours, 90% of the p-dimethylaminoazo-benzene initially added had disappeared and as much as 85% was accounted for in the form of the monomethyl derivative. Thereafter, the amount of p-monomethylaminoazo-benzene decreased. Small amounts of p-aminoazobenzene also were formed. The demethylation occurred only during autoxidation; none was found when the oxidation was inhibited with tocopherol.
Get full access to this article
View all access options for this article.