Benzoquinone imines. Part X. The mechanism and kinetics of the reactions of p-benzoquinone di-imine and p-benzoquinone monoimine with C-methoxy-m-diamines and p-methoxy- and p-chloro-phenols

Abstract

In its reaction with p-benzoquinone imines, 2,4-diaminoanisole behaves as a normal 4-equivalent coupler with the rate controlling coupling reaction occurring in the 5-position. The reaction of imines with 1,5-dimethoxybenzene-2,4-diamine or 5-methoxytoluene-2,4-diamine involves initial coupling at both the 1- and 5-positions, followed by elimination of methanol and/or dissociation of the adduct. With monoimine, the coupling step is rate controlling while with di-imine it is rate controlling at only high pH with the elimination step becoming rate controlling at low pH. The reactions of p-benzoquinone di-imine with p-methoxyphenol and with 4-chloro-2,5-xylenol involve initial, rate controlling, coupling at the 4-position followed by rapid elimination of methanol or hydrogen chloride respectively. The coupling steps have a similar pH dependence to that reported previously for the coupling of p-benzoquinone imines with simple m-diamine and phenolic couplers.