Hydrogen exchange between molecular tritium and bibenzyl in solution catalyzed by transition metals

The hydrogen-tritium exchange between gaseous tritium and bibenzyl catalyzed by some metals of the VIIIth group, is investigated. The reactions are performed in dioxane, at room temperature and initial tritium gas pressure of 100-130 mm Hg. The exchange occurs only when the oxide form of the metal catalyst is pre-reduced by tritium. This reduction has been found to be a stoichiometric reaction. The efficiency of labelling is proportional to the amount of tritium involved in the activation of the catalyst and to the bibenzyl concentration. It is also dependent on the choice of solvent. The highest specific activity of bibenzyl obtained is 11·2 Ci/mmol. The proposed mechanism for the exchange reaction involves an intermediate step wherein adsorbed tritium, in the hydride or the hydroxyl form, acts on the adsorbed substrate.