KINETICS AND MECHANISM OF THE ADDITION OF TRIPHENYLPHOSPHONIOCYCLOPENTADIENIDE TO TETRAHALOGENO-P-BENZOQUINONES .4. THE SUBSTITUTION-REACTIONS OF FLUORANIL

Fluoranil reacts with excess triphenylphosphoniocyclopentadienide to y ield the monosubstituted and 2.6-disubstituted quinone derivatives thr ough two parallel. irreversible, second-order reactions which are well separated in time. The rate of formation of the monosubstitution prod uct was resolved using the stopped-flow technique and its half-rite wa s found to be in the millisecond range. Kinetic data for the mono- and di-substitution products indicate that both reactions proceed in two steps involving rate-limiting addition to form a polar betaine interme diate followed by elimination of hydrogen halide through an E1 mechani sm.-The empirical rate law was established by carrying out a multi-res ponse non-linear least-square analysis of the absorbance of the reacti on mixtures.