This thesis is concerned with the preparation of regiospecifically labelled compounds by homogeneous metal catalysed hydrogen isotope exchange reactions. The features of homogeneous hydrogen isotope exchange reactions are discussed in Chapter 1, along with other exchange methods; acid, base, heterogenous metal, radiation, enzymic and zeolite catalysis. In Chapter 2, homogeneous rhodium trichloride is investigated for regiospecificity of tritium labeling in a wide range of aromatic compounds. High regiospecificity of labelling ortho to carboxyl, carboxamide and methanamide groups is found, with the regiospecificity determined by 3H nmr spectroscopy. Also discussed is a study to determine whether any other Group VIII metal complexes will catalyse the ortho tritiation of benzoic acid, in addition to rhodium trichloride. The results of detritiation studies performed on benzoic acids using ruthenium acetylacetonate as catalyst as a model for rhodium trichloride are presented in Chapter 3, A possible reaction mechanism is also presented. Finally, an application of the rhodium trichloride system to the labelling of biologically useful molecules is discussed in Chapter 4. The deuteration and tritiation of a number of drugs and metabolites containing known ortho directing groups is described. In a large number of cases, the regiospecificity for ortho labelling is very high.

Hydrogen isotope separation systems using palladium (Pd) are currently being designed for both reactor designs with the aim of separating and purifying the reactor exhaust products which contain valuable unspent hydrogen isotopes. Hydrogen isotope exchange in Pd offers an efficient, ambient condition process that can produce pure isotopic species in a process far simpler and less costly than the current state of the art cryogenic distillation processes. The method is applicable whether separating hydrogen (protium), deuterium or tritium and any combination of these. If practical fusion devices are ever to be realised it is essential to produce an economical and efficient fuel cycle capable of separating and purifying hydrogen isotopes. Hydrogen isotope exchange in Pd is also of interest to the waste separation and purification industries, in particular those using hydrogen separation membranes which used Pd and Pd-alloy membranes. Understanding hydrogen isotope exchange, with particular regard to the formation of the intermediate (and often unwanted) hydrogen deuteride (HD), will aid significantly in future designs of hydrogen isotope separation systems. Novel hydrogen isotope exchange experiments involving hydrogen and deuterium at a number of temperatures (208 K, 293 K and 373 K) and pressures (1.3 bar – 8 bar) not yet explored are presented in this thesis. The experiments were carried out on a unique piece of laboratory apparatus provided to and further developed at the University of Bath. Alongside experimentation, a novel comprehensive multidimensional multi-physics model has been created to analyse the experimental data obtained using the new apparatus and elucidate the kinetics and mechanisms of the reactions occurring between hydrogen isotopic species and Pd during hydrogen isotope exchange based on Langmuir-Hinshelwood surface reaction mechanism. The surface reaction rates, kinetic rate constants and heat effects have been examined in detail, and in tandem, for the first time.

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