Polarographic Study of Acid-Base Reactions of the Tropylium Ion

Abstract

A POLAROGRAPHIC study of the tropylium ion (C7H7+) in unbuffered media1 did not permit any quantitative interpretation of the acid-base phenomena at the surface of the mercury dropping electrode. We therefore followed the reduction of the tropylium ion in well-buffered media. At concentrations lower than about 0.00015 M one irreversible reduction wave was observed. The height of this wave decreased with increasing pH in the form of a dissociation curve (Fig. 2) with pK′ = 5.64 at t 1 = 3.3 sec. The kinetic current at higher pH values is limited by the rate of formation of the reducible tropylium cation from electro-inactive tropyl alcohol, which is present in the solution and is brought by diffusion to the surface of the mercury electrode.