Collect. Czech. Chem. Commun. 1990, 55, 1216-1222

Kinetics of reaction of 1,2-diaminobenzene with phenylglyoxal

Jiří Klicnar, Jaromír Mindl and Vojeslav Štěrba

Department of Organic Chemistry, Institute of Chemical Technology, 532 10 Pardubice


The cyclization reaction kinetics of phenylglyoxal monohydrate with 1,2-diaminobenzene have been studied in formate, acetate, and phosphate buffers. At high pH values and low buffer concentrations the rate-limiting step consists in the protonation of the intermediate formed by addition of the first amino group to aldehydic group of phenylglyoxal. With increasing concentrations of formate and acetate buffers the rate-limiting step shifts to the formation of the intermediate. In phosphate buffers the catalysis by the basic buffer component makes itself felt, too. At higher concentrations of 1,2-diaminobenzene, the dehydration of phenylglyoxal monohydrate gradually becomes the rate-limiting step.