Abstract The rate constants k 2 and equilibrium constants K= k 2/k-2 of the title process (A) have been measured in aqueous solutions of eight quaternary salts of nicotinamide I (R= p- XC 6 H 4 CH 2) at 298 K. The substituent effects of X= CH 3 O, CH 3, H, F, Cl, COOCH 3, CN, and NO 2 exhibiting the Hammett dependence have been correlated with half-wave potentials of reduction of the depolarizers I, and the correlation results have been ...