Nonmetallic palladium‐on‐resin: A very active and selective catalyst for the hydrogenation of diunsaturated fatty acid esters I

Methyl cis ‐9, cis ‐12‐octadecadienoate (methyl linoleate; c 9, c 12) and the corresponding cis,trans and trans.trans geometric isomers ( c 9, t 12 and t 9, t 12) were hydrogenated at 40 C and atmospheric hydrogen pressure in acetone as solvent, with nonmetallic palladium‐on‐resin catalyst. These catalysts were prepared by impregnation of cationic exchange resins with an aqueous solution of palladium dichloride. The methyleneinterrupted dienes were hydrogenated to the monoene stage with almost infinite selectivity, especially with c 9, c 12, whereas t 9, t 12 was hydrogenated somewhat less selectively. The latter isomer was reduced considerably more slowly than the first, whereas c 9, t 12 occupied an intermediate position. The hydrogenation proceeded for an important part via a straightforward reduction of one of the double bonds, though conjugation prior to hydrogenation also occurred. The methylene‐interrupted dienes isomerized to a high degree geometrically during hydrogenation, but they scarcely isomerized positionally, resulting in small amounts of inactive ethylene‐interrupted dienes.