Heterogeneous palladium-catalyzed exchange labelling of representative organic compounds with tritium gas

Article abstract of DOI:10.1002/jlcr.2580360102

A range of organic substrates was successfully exchanged with tritium gas using NaBH₄-reduced palladium oxide or chloride as catalyst. Exchange conditions involved a reaction temperature of 100°C, a reaction time of 3 days, and products were analyzed by radio-gas chromatography and ³H NMR spectroscopy. Both aromatic and aliphatic compounds underwent exchange, 18 of the 22 substrates incorporated >35% of the available tritium, and most products showed high radiochemical purity. ³H NMR analyses showed that both alkanes and the alkyl chains of alkylbenzenes were rapidly and evenly labelled. Some aromatic compounds showed general ring exchange while others showed high specificity. These results for hulk palladium catalyst are strikingly different from those obtained with bulk platinum and supported palladium catalysts. The results are discussed in terms of currently accepted mechanisms of heterogeneous metal catalyzed hydrogen isotope exchange reactions.