Kinetics and mechanism of the addition of triphenylphosphoniocyclopentadienide to tetrahalo-p-benzoquinones. Part III. The disubstitution of chloranil and bromanil

Abstract

Chloranil and bromanil react with an excess of triphenylphosphoniocyclopentadienide to yield the 2,5- and 2,6-disubstituted quinone derivatives through two parallel, second-order reactions. Kinetic data suggest that the reaction proceeds in two steps, involving addition to form a polar betaine intermediate followed by elimination of hydrogen halide. The activation parameters strongly suggest that the loss of halide is of the E₁ type. The empirical rate law has been established carrying out a multi-response non-linear least-squares analysis followed by a Gaussian de-convolution of the visible spectra of the reaction mixtures.