Antioxidant activity of phenols as related to effects of substituent groups

Summary Antioxidant activity in lard was exhibited by all phenols which had electron‐repelling groups in the 2 and 6 positions. No activity was shown by those which had electron‐attracting groups in these positions. The mechanism of antioxidant action of alkyl phenols in lard does not appear to differ from that of di‐ or polyphenols. A free phenolic group was shown to be essential, and spectral absorption studies after autoxidation did not reveal any evidence for a dimer of the alkyl phenol. The dimer, stilbene quinone, reported isolated from oxidized petroleum oil, disappeared quite rapidly when added to oxidizing lard.