STUDIES ON LABILE CHARGETRANSFER COMPLEXES BETWEEN O-CHLORANIL AND A SERIES OF PHENOLS

The electron donor-acceptor (EDA) interactions between o-chloranil and a series of phenols have been studied in dioxan medium. Except for re sorcinol, the EDA complexes are formed instantaneously on mixing the d onor and the acceptor solutions and then they decay slowly into second ary products. In case of resorcinol, formation and decay of the EDA co mplex are slow and simultaneous. The kinetics of all these reactions h ave been studied spectrophotometrically and the formation constants of EDA complexes have been determined from kinetic data. The hv(CT) valu es change systematically as the number and position of the -OH groups change in the aromatic ring of the phenol moiety. From the trends in t he hv(CT) values, the Huckel parameters (h((O) double over dot) and k( C-(O) double over dot)) for the -OH group, required for a PMO calculat ion on phenols, have been obtained in a straightforward way and the va lues so obtained, viz., 1.8 and 1.0 respectively, are close to the one s (1.8 and 0.8) recommended by Streitwieser on the basis of other evid ences. (C) 1997 Elsevier Science B.V.