216585-42-1Relevant articles and documents
General base and general acid catalyzed intramolecular aminolysis of esters. Cyclization of esters of 2-aminomethylbenzoic acid to phthalimidine
Fife, Thomas H.,Chauffe
, p. 3579 - 3586 (2000)
Plots of log K0 vs pH for the cyclization of trifluoroethyl and phenyl 2-aminomethylbenzoate to phthalimidine at 30 °C in H2O are linear with slopes of 1.0 at pH >3. The values of the second-order rate constants KOH for apparent OH- catalysis in the cyclization reactions are 1.7 × 105 and 5.7 × 107 M-1 s-1, respectively. These rate constants are 105- and 107-fold greater than for alkaline hydrolysis of trifluoroethyl and phenyl benzoate. The KOH for cyclization of the methyl ester is 7.2 × 103 M-1 s-1. Bimolecular general base catalysis occurs in the intramolecular nucleophilic reactions of the neutral species. The value of the Bronsted coefficient β for the trifluoroethyl ester is 0.7. The rate-limiting step in the general base catalyzed reaction involves proton transfer in concert with leaving group departure. The mechanism involving rate-determining proton transfer exemplified by the methyl ester in this series (β = 1.0) can then be considered a limiting case of the concerted mechanism. General acid catalysis of the neutral species reaction or a kinetic equivalent also occurs when the leaving group is good (pKa ≤ 12.4). That the mechanism and/or rate-determining step of the intramolecular aminolysis reactions is different than in bimolecular reactions or the intramolecular reactions of other esters is attributed to the excellent steric fit of the nucleophile to the reaction center of the 2-aminomethylbenzoate esters.
Kinetic study of hydrolysis of benzoates. Part XXV. Ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in water
Nummert, Vilve,Piirsalu, Mare,Maeemets, Vahur,Koppel, Ilmar
, p. 107 - 128 (2007/10/03)
The second-order rate constants k2 for alkaline hydrolysis of phenyl esters of meta-, para-and ortho-substituted benzoic acids, X-C 6H4CO2C6H5 (X = H, 3-Cl, 3-NO2, 3-CH3, 4-NO2, 4-Cl, 4-F, 4-CH 3, 4-OCH3, 4-NH2, 2-NO2, 2-CN, 2-F, 2-Cl, 2-Br, 2-I, 2-CH3, 2-OCH3, 2-CF3, 2-NH2), and of substituted phenyl esters of benzoic acid, C 6H5CO2C6H4-X (X = 2-I, 2-CF3, 2-C(CH3)3, 4-Cl, 4-CH3, 4-OCH3, 4-NH2), have been measured spectrophotometrically in water at 25 °C. The substituent effect in alkaline hydrolysis of phenyl esters of para-substituted benzoic acids, similar to that for ethyl esters of para-substituted benzoic acids, was found to be precisely described by the Hammett relationship (p = 1.7 in water). The log k value for alkaline hydrolysis of phenyl and ethyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2R, was nicely correlated with log km,p,ortho = log ko + (ρ)m,pσ + (ρI)orthoσI + (ρ° R)orthoσ°R + δ orthoΕsB where σ, σI, σ°R are the Hammett polar, Taft inductive and Taft resonance (σ°R = σ° - σI) substituent constants, respectively. Ε SB is the steric scale for ortho substituents calculated on the basis of the log k values for the acid hydrolysis of ortho-substituted phenyl benzoates in water owing to the ortho substituent in the phenyl of phenyl benzoates. In water, the main factors responsible for changes in the ortho substituent effect in alkaline hydrolysis of phenyl and ethyl esters of ortho-substituted benzoic acids, X-C6H4CO2R, were found to be the inductive and steric factors while the role of the resonance term was negligible ((ρ°R)ortho ca. 0.3). In alkaline hydrolysis of substituted benzoates in neat water, the ortho inductive effect appeared to be 1.5 times and steric influence 2.7 times higher than the corresponding influences from the ortho position in the phenyl of phenyl benzoates. The contributions of the steric effects in alkaline hydrolysis of esters of ortho-substituted benzoic acids was found to be approximately the same as in acid hydrolysis of esters of ortho-substituted benzoic and acid esterification of ortho-substituted benzoic acids.
