29980-76-5Relevant articles and documents
SYNTHESIS AND CYCLIZATION KINETICS AND MECHANISM OF 1-(2-ETHOXYCARBONYLPHENYL)-3-ARYLTRIAZENES. KINETIC ACIDITY FUNCTION OF SODIUM METHOXIDE IN METHANOL
Pytela, Oldrich,Dlouhy, Vladimir
, p. 2468 - 2474 (2007/10/02)
Eight 1-(2-ethoxycarbonylphenyl)-3-aryltriazenes have been synthetized and the rate constants of their sodium-metoxide-catalyzed cyclization have been measured in methanol at 25.0 deg C.The experimental rate constants kobs have been adopted to construct the kinetic acidity function HKM which has been shown to be identical with the -log -> values.Two mathematical procedures have been used to determine the catalytic rate constants and their dependence on the Hammett substituent constants.A closer dependence is obtained with the ? values than with the?p- values.The Q value found (0.3) indicates a compensation of the substituent effects upon the dissociation of the starting triazene and upon the subsequent reaction of the conjugated base.Out of the two mechanistic alternatives - E1cB and BAc2 - the latter appears to be more probable, the splitting of tetrahedral intermediate being its limiting step.