The platinum-catalyzed isotopic exchange reaction of aromatic compounds.

Abstract

Partial protonation (10--12 atom% H) of a series of perdeuteriomonosubstituted aromatic compounds (98--99.5 atom% D) was effected by exchange with water in the presence of activated platinum metal. The products were subjected to analyses by mass-spectrometry and N.M.R. spectrometry. From a knowledge of the amount of protium introduced in the ortho, meta and para positions, partial rate factors for each of a series of monosubstituted benzenes were calculated. A correlation was found with the A values reported in the literature for the steric effect of different substituents. No relationship between electronic factors and directive effects of the substituent was apparent. The data obtained are interpreted with respect to the most likely mechanism for the exchange reaction.