KINETICS AND MECHANISM OF DECOMPOSITION OF 1,3-BIS(4-METHYLPHENYL)TRIAZENE CATALYZED WITH SUBSTITUTED BENZOIC-ACIDS IN 25-PERCENT AQUEOUS-METHANOL - GENERAL OR SPECIFIC CATALYSIS

The kinetics of decomposition of 1,3-bis(4-methylphenyl)triazene catal yzed with 13 substituted benzoic acids of various concentrations have been measured in 25 vol.% aqueous methanol at 25.0 degrees C. The rate constants observed (297 data) have be used as values of independent v ariable in a series of models of the catalyzed decomposition. For the catalytic particles were considered the undissociated acid, its conjug ated base, and the proton in both the specific and general catalyses. Some models presumed formation of reactive or nonreactive complexes of the individual reactants. The substituent effect is described by the Hammett equation. The statistically best model in which the observed r ate constant is a superposition of a term describing the dependence on proton concentration and a term describing the dependence on the prod uct of concentrations of proton and conjugated base is valid with the presumption of complete proton transfer from the catalyst acid to subs trate, which has been proved. The behaviour of 4-dimethylamino, 4-amin o, and 3-amino derivatives is anomalous (lower catalytic activity as c ompared with benzoic acid). This supports the presumed participation o f conjugated base in the title process.