Reactions of lead tetra-acetate. Part XIV. The base-catalysed decomposition of lead tetra-acetate in acetic acid

Abstract

The rate of reduction of lead(IV) in solutions of lead tetra-acetate in acetic acid containing a base (sodium acetate, pyridine, or triethylamine) is increased by the addition of each of the chloroacetic acids (dichloro > monochloro > trichloro). The rate for the sodium acetate-catalysed reaction does not follow integral-order kinetics, but as the concentration of lead tetra-acetate is reduced it approaches increasingly closely to kinetics which are of the first order with respect to each reactant. When the decomposition of lead tetra-acetate in acetic acid containing sodium acetate or pyridine is interrupted, a complex can be isolated which readily reverts to lead tetra-acetate; osmometric measurements suggest that it is a binuclear PbIV species. The results are accommodated by the view that the base-catalysed destruction of (mononuclear) PbIV occurs concurrently with reaction leading to the complex in which the PbIV is reduced less rapidly. A mechanism for the base-catalysed reduction is suggested.