Collect. Czech. Chem. Commun. 1991, 56, 386-397

Azo coupling kinetics of benzenediazonium ions with citrazinic acid

Jaroslava Horáčkováa, Jaromír Kaválekb, Jiří Kuliča and Vojeslav Štěrbab

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


Azo coupling kinetics of 4-methoxybenzenediazonium ion with 1,2-dihydro-6-hydroxy-2-oxopyridine-4-carboxylic acid (citrazinic acid, Ia) have been measured in dilute solutions of hydrochloric acid and in chloracetate, ethoxyacetate, acetate, and dihydrogenphosphate buffers. The reaction is subject to general base catalysis, i.e. splitting off of the proton from the tetrahedral intermediate is the rate-limit step. The rate constants have been measured for the azo coupling reaction with monoanion III (splitting off of the proton from OH group) and dianion. The rate constant with the monoanion III is only 4x smaller than that with the dianion and practically the same as that with the anion of citrazinic acid ester VIII. The azo coupling rte constants of the monoanion III have been determined for various substituted benzenediazonium ions, the ρ value found is 4.85.