The catalytic exchange properties of a
number of organic compounds containing nitrogen, sulphur, or arsenic have been
studied in the presence of benzene and heavy water. The results confirm a
charge-transfer-no-bond adsorption mechanism previously proposed for the
deuteration of aromatic polycyclic hydrocarbons. For aromatic nitrogen
compounds an increase in ionization potential of substrate leads to an increase
in deuterium incorporation and a decrease in catalyst poisoning. Some aromatic
amines deuterate faster than expected by theory and this is attributed to rapid
exchange of the amino hydrogens in heavy water with a consequential increase in
D-H ratio at the catalyst; surface. Sulphur and arsenic, even in their
saturated valency states, extensively poison benzene exchange as does
triethylamine. p-Benzoquinone, 2,6-dichloroquinone, and NN-dimethyl benzylamine
exhibit catalytic side reactions which poison benzene exchange. With tritium
oxide, the technique is suitable for the synthesis of tritiated aromatic amines
and heterocycles to high specific activity.
