Selective Hydrogenation of Polyethenoid Fatty Compounds: a Possible Mechanism

Abstract

IT has long been known^1,2 that, when a mixture of linoleic and oleic glycerides is catalytically hydrogenated, the linoleic groups are reduced to the mono-ethenoid condition before any appreciable quantity of saturated (stearic) glycerides is produced. Whereas this selectivity is extremely marked in glycerides or other mixtures of unsaturated esters, it is much less prominent when corresponding mixtures of unsaturated acids are hydrogenated². Further, Richardson et al.³ observed that selectivity is not so fully developed during hydrogenation of whale or other marine animal oils, wherein polyethenoid acids of the C₁₈, C₂₀ and C₂₂ series are prominent ; and Harper, Hilditch and Terleski⁴ showed that up to a very late stage in the hydrogenation of whale oil or cod liver oil, definite proportions of unsaturated glycerides containing more than one ethenoid group persist.