132639-95-3Relevant academic research and scientific papers
Steric effects in acid-catalyzed decomposition and base-catalyzed cyclization of 1-(2-alkoxycarbonyl-phenyl)-3-phenyltriazenes
Pytela, Oldrich,Halama, Ales
, p. 751 - 763 (2007/10/03)
Eight derivatives of 1-(2-alkoxycarbonylphenyl)-3-phenyltriazene (R = methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, and allyl) have been synthesized and their UV-VIS, IR, 1H and 13C NMR spectra measured. The NMR spectra have been interpreted in detail. The kinetics of acid-catalyzed decomposition and base-catalyzed cyclization of the title compounds have been measured in 52.1% w/w methanol at 25.0 °C. The unit reaction order has been verified and the cyclization product has been identified. The pH-profiles obtained have been used to calculate the catalytic rate constants kA (acid-catalyzed decomposition) and kB (base-catalyzed cyclization) of all the derivatives; the constants have been interpreted with regard to inductive and steric effects. The catalytic rate constant kA has been found to be independent of the substituents. The catalytic rate constant kB depends statistically significantly upon both inductive and steric effects, the sensitivity to the former being more significant. The experimental results and their interpretation confirm the base-catalyzed cyclization mechanism with formation of tetrahedral intermediate as the rate-limiting step.
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.
