Monohydroxylation of unsaturated oils: III. Use of halogen intermediates

Abstract

AbstractHydroxylation of safflower and linseed oils by routes involving halogen compounds is described. A product containing 20.5% Br was obtained by treatment of safflower oil in CCl4 solution with N‐bromosuccinimide (NBS) in presence of benzoyl peroxide and UV illumination. Bromine was totally removed using Ag2O in 50% dioxan; the resulting hydroxyl value (HV) was only 100, against an expected HV of 180, perhaps because of dehydration and ether formation. Using other silver salts, bromine replacement with hydroxyl was always incomplete. Such residual bromine was totally replaced by hydrogen, without altering other characteristics, by treatment of the product with zinc amalgam in acetic acid. Linseed oil by similar NBS bromination (Br 22.2%) and Ag2O treatment gave a product with Br 2.9%, HV 74, conj. diene 15% and conj. triene 4%. Halogenreplacement difficulties also attended the hydrobromination of these oils at the double bonds, followed by hydroxylation. Addition of hypochlorous or hypobromous acid to safflower oil, followed by total replacement of halogen with hydrogen using zinc amalgam, yielded products of HV 75 and 83 respectively. The degree of hydroxylation was only half of that expected from the loss of unsaturation.