Study on the Reaction of Higher Fatty Acid Methyl Esters with Metallic Sodium. VIII.

Abstract

Bouveault et Blanc reduction of oleic, erucic, debrominated linoleic and linolenic acid methyl esters was studied for the purpose of examining the properties and isomerization of unsaturated fatty alcohols. No geometrical isomer was observed by the infrared spectroscopic study in the case of esters of monoethylenic acids such as oleic and erucic acid. With increase of the number of double bonds the yield of the fatty alcohol slightly decreased. It shows that Bouveault et Blanc reduction has a little effect on the double bond of dienoic and trienoic acid esters.From the ultraviolet spectroscopy linolenyl alcohol contains more conjugated double bonds than linoleyl alcohol, showing that the higher content of double bonds favors the more rapid conjugation when reduced under the same condition. If the alcohol produced would be treated during a prolonged period in the reaction vessel, the conjugated double bonds contained in the alcohol decrease to be lower than that of the raw ester.When methyl linoleate and linolenate are reduced with excess of reducing alcohol, metallic sodium reacts priorly with raw ester and reducing alcohol, resulting more conjugation compared with the case whereby reducing alcohol is not excess.Isomerization reaction on the reduction of dienoic and trienoic acid esters was discussed.