Collect. Czech. Chem. Commun. 1988, 53, 3154-3163

Reaction kinetics of 1,2-diaminobenzene with ethyl 2-oxopropanoate and 2,3-butanedione

Jiří Klicnara, Jaromír Mindla, Ivana Obořilováb, Jaroslav Petříčekc and Vojeslav Štěrbaa

a Department od Organic Chemistry, Institute of Chemical Technology, 532 10 Pardubice
b VCHZ Synthesia, 533 54 Pardubice-Semtin
c Chemopetrol, 530 06 Pardubice


The reaction of 1,2-diaminobenzene with 2,3-butanedione is subject to general acid catalysis in acetate and phosphate buffers (pH 4-7). The rate-limiting step of formation of 2,3-dimethylquinoxaline consists in the protonation of dipolar tetrahedral intermediate. In the case of the reaction of 1,2-diaminobenzene with ethyl 2-oxopropanoate, the dehydration of carbinolamine gradually becomes rate-limiting with increasing pH in acetate buffers, whereas in phosphate buffers a new reaction pathway makes itself felt, viz. the formation of amide catalyzed by the basic buffer component and by hydroxide ion.