Equilibria and Kinetics of the Redox Reaction of p‐Benzoquinone Monoimine with NN‐Dialkylsubstituted p‐Phenylenediamine

Abstract

AbstractThe kinetics as well as the equilibrium of the redox reactionmagnified image(where QMI = 3‐methylbenzoquinone 4‐imine, PPD = 4‐aminc‐N‐ethyl‐N‐(2‐methylsulphonamidoethyl)‐3‐methylaniline, QDI+ = diimine corresponding to PPD, PAC = 3‐methyl‐4‐aminophenol) have been investigated at 22°. The equilibrium quotient of the above reaction and its dependence on pH (in the range from pH 8.0 to 10.8) has been evaluated from potentiometric measurements of the redox potentials of the half‐reactions di‐imine/diamine and monoimine/aminophenol. The kinetics of the overall reaction was investigated by mixing in a stopped‐flow spectrophotometer a solution of QMI with a mixture of PPD and a properly chosen colour former reacting with QDI as well as with QMI with dye formation, and by monitoring the variation of absorbance with time. The kinetic constants were evaluated with the aid of a computer. Their pH dependence is discussed in terms of the protonation of reacting species.