32792-81-7Relevant academic research and scientific papers
Evidence of substituent-induced electronic interplay. Effect of the remote aromatic ring substituent of phenyl benzoates on the sensitivity of the carbonyl unit to electronic effects of phenyl or benzoyl ring substituents
Neuvonen, Helmi,Neuvonen, Kari,Pasanen, Paavo
, p. 3794 - 3800 (2007/10/03)
Carbonyl carbon 13C NMR chemical shifts δC(C=O) measured in this work for a wide set of substituted phenyl benzoates p-Y-C 6H4CO2C6H4-p-X (X = NO2, CN, Cl, Br, H, Me, or MeO; Y = NO2, Cl, H, Me, MeO, or NMe2) have been used as a tool to study substituent effects on the carbonyl unit. The goal of the work was to study the cross-interaction between X and Y in that respect. Both the phenyl substituents X and the benzoyl substituents Y have a reverse effect on δC(C=O). Electron-withdrawing substituents cause shielding while electron-donating ones have an opposite influence, with both inductive and resonance effects being significant. The presence of cross-interaction between X and Y could be clearly verified. Electronic effects of the remote aromatic ring substituents systematically modify the sensitivity of the C=O group to the electronic effects of the phenyl or benzoyl ring substituents. Electron-withdrawing substituents in one ring decrease the sensitivity of δC(C=O) to the substitution of another ring, while electron-donating substituents inversely affect the sensitivity. It is suggested that the results can be explained by substituent-sensitive balance of the contributions of different resonance structures (electron delocalization, Scheme 1).
Imidazole-Catalyzed Hydrolysis of Substituted Benzoate Esters. A Detailed Kinetic and Mechanistic Study
Menegheli, Paulo,Farah, Joao P. S.,Seoud, Omar A. El
, p. 1610 - 1615 (2007/10/02)
Kinetic and mechanistic details of the imidazole-catalyzed hydrolysis of substituted phenyl benzoates in 10percent acetonitrile in water (V/V) were examined.The following 4 ester series were studied: p-nitrophenyl p-X-benzoates (X = CH3, H, Cl, CN, NO2, series I), p-Y-phenyl p-nitrobenzoates (Y = CH3, H, Cl, CN, NO2, series II), 2,4-dinitrophenyl p-X-benzoates (X = CH3O, H, Cl, CN, NO2, series III) and p-Y-phenyl 2,4-dinitrobenzoates (Y = CH3, H, Cl, CN, NO2, series IV).Based on: catalytic rate constants, activation parameters, kinetic solvent isotope effects, Hammett (ρ) values and the spectroscopic detection of the reaction intermediates, the following conclusions were reached: a) imidazole acts as a nucleophilic catalyst, i.e., the hydrolysis occurs via the intermediate formation of acylimidazole; b) the leaving group is the phenoxide ion; c) the rate limiting step is the decomposition of the tetrahedral intermediate that precedes the acylimidazole (series I, II and IV) or the attack of imidazole on the acyl group of the ester (series III). Keywords: Acylimidazoles / Catalysis / Chemical Kinetics / Isotope Effects / Reaction Mechanism
