Isotopic effects during catalytic hydrogenation

No isotopic discrimination is observed during catalytic reduction of methyl oleate with hydrogen‐tritium gas mixtures. One explanation may be that at atmospheric pressure and 40C the isotopic effect on solubility is small and the concentration of the dissolved hydrogen isotopes is rate limiting. Tritium in methyl 9‐octadecenoate‐9,10‐T is not released during saturation of the double bond but appears in the gaseous phase upon completion of hydrogenation, as indicated by an ion chamber. No isotopic discrimination is observed in the reduction of methyl oleate with mixtures of hydrogen, deuterium, and tritium; however, a mass spectrometer indicates an increase in the hydrogen‐deuterium ratio during hydrogenation. Under the conditions described, tritium and deuterium may be used to study the mechanism of hydrogenation without significant isotopic effects.