Hydrogenation of methyl oleate in solvents

The hydrogenation of the oleic acid group was investigated with the objective of determining the effect of solvents on the reaction rate and the formation of positional and geometrical isomers. Methyl oleate, either alone or dissolved in one of several solvents, hexane, ethanol, n ‐butyl ether, or acetic acid, was hydrogenated to an iodine value of about 50 under atmospheric pressure and at 30°C, with palladium‐on‐carbon and the W‐5 form of Raney nickel as catalysts. Hydrogenation with palladium catalyst, with or without solvents, produced 76.6 to 79.1% trans bonds, based on the total double bonds. This is significantly greater than the 67% obtained previously. Hydrogenation products obtained with Raney nickel and solvents contained as little as 20.7% trans bonds at an iodine value of about 50. In two cases the trans bonds were equal to about one‐third the positional isomers. Positional isomers formed extensively when the Raney nickel was used in the absence of solvents and when the palladium catalyst was used. When the Raney nickel and solvents were used large proportions of double bonds were found in the original 9‐position.