SUBSTITUENT EFFECTS ON THE LIFETIMES AND REACTIVITIES OF ARYLNITRENIUM IONS STUDIED BY LASER FLASH-PHOTOLYSIS AND PHOTOTHERMAL BEAM DEFLECTION

Photolysis of 5-substituted-N-tert-butyl-3-methylanthranilium produces transient N-tert-butyl-(2-acetyl-4-substituted) phenylnitrenium ions. This is confirmed by identification of the stable products, transient absorption experiments, and photothermal beam deflection experiments. Analysis of the stable photoproducts shows that the major decay pathw ay for these species is addition of nucleophiles to the aromatic ring. The kinetics of the these reactions were examined with the goal of de termining how various ring substituents affect arylnitrenium ion stabi lity. Rate constants measured for the 4-phenyl and 4-methoxy derivativ es are compared with those from previous work. It is shown that a 4-ph enyl group stabilizes the nitrenium ion to approximately the same exte nt as a 4-methoxy group. Both of these substituents stabilize the aryl nitrenium ions considerably more than 4-halogens or a 4-methyl group. Time resolved photothermal beam deflection experiments were applied to the 4-cyano and 4-unsubstituted derivatives, which gave no transient absorption spectra. The latter two compounds are shown to have lifetim es of less than 100 ns.