Kinetic Study on Alkaline Hydrolysis of 2-Pyridyl and 4-Pyridyl X-substituted-Benzoates: Effects of Benzoyl Substituent X and Leaving-Group Basicity on Reactivity and Reaction Mechanism

2017 ◽  
Vol 38 (10) ◽  
pp. 1138-1142 ◽  
Author(s):  
Young-Hee Shin ◽  
Han-Joong Koh ◽  
Ik-Hwan Um
Keyword(s):  
Reaction Mechanism ◽  
Kinetic Study ◽  
Alkaline Hydrolysis ◽  
Leaving Group ◽  
Hydrolysis Of

Kinetic Study of Hydrolysis of Benzoates. Part XXVI. Variation of the Substituent Effect with Solvent in Alkaline Hydrolysis of Substituted Alkyl Benzoates

2006 ◽  
Vol 71 (11-12) ◽  
pp. 1557-1570 ◽  
Author(s):  
Vilve Nummert ◽  
Mare Piirsalu ◽  
Ilmar A. Koppel
Keyword(s):  
Kinetic Study ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Substituent Effect ◽  
Substituent Effects ◽  
Alkyl Substituent ◽  
Solvent Parameters ◽  
Substituent Constants ◽  
Hydrolysis Of ◽  
Main Factor

The second-order rate constants k2 (dm3 mol-1 s-1) for the alkaline hydrolysis of substituted alkyl benzoates C6H5CO2R have been measured spectrophotometrically in aqueous 0.5 M Bu4NBr at 50 and 25 °C (R = CH3, CH2Cl, CH2CN, CH2C≡CH, CH2C6H5, CH2CH2Cl, CH2CH2OCH3, CH2CH3) and in aqueous 5.3 M NaClO4 at 25 °C (R = CH3, CH2Cl, CH2CN, CH2C≡CH). The dependence of the alkyl substituent effects on different solvent parameters was studied using the following equations:      ∆ log k = c0 + c1σI + c2EsB + c3∆E + c4∆Y + c5∆P + c6∆EσI + c7∆YσI + c8∆PσI     ∆ log k = c0 + c1σ* + c2EsB + c3∆E + c4∆Y + c5∆P + c6∆Eσ* + c7∆Yσ* + c8∆Pσ* .  ∆ log k = log kR - log kCH3. σI and σ* are the Taft inductive and polar substituent constants. E, Y and P are the solvent electrophilicity, polarity and polarizability parameters, respectively. In the data treatment ∆E = ES - EH2O , ∆Y = YS - YH2O , ∆P = PS - PH2O were used. The solvent electrophilicity, E, was found to be the main factor responsible for changes in alkyl substituent effects with medium. When σI constants were used, variation of the polar term of alkyl substituents with the solvent electrophilicity E was found to be similar to that observed earlier for meta and para substituents, but twice less when σ* constants were used. The steric term for alkyl substituents was approximately independent of the solvent parameters.

Effect of Medium on Reactivity for Alkaline Hydrolysis of p-Nitrophenyl Acetate and S-p-Nitrophenyl Thioacetate in DMSO-H2O Mixtures of Varying Compositions: Ground State and Transition State Contributions

2021 ◽  
Author(s):  
Ik-Hwan Um ◽  
Seungjae Kim
Keyword(s):  
Transition State ◽  
Alkaline Hydrolysis ◽  
Ground State ◽  
Rate Constants ◽  
Kinetic Data ◽  
Reaction Medium ◽  
Stepwise Mechanism ◽  
Rate Determining Step ◽  
Leaving Group ◽  
Hydrolysis Of

Second-order rate constants (kN) for reactions of p-nitrophenyl acetate (1) and S-p-nitrophenyl thioacetate (2) with OH‒ have been measured spectrophotometrically in DMSO-H2O mixtures of varying compositions at 25.0 ± 0.1 oC. The kN value increases from 11.6 to 32,800 M‒1s‒1 for the reactions of 1 and from 5.90 to 190,000 M‒1s‒1 for those of 2 as the reaction medium changes from H2O to 80 mol % DMSO, indicating that the effect of medium on reactivity is more remarkable for the reactions of 2 than for those of 1. Although 2 possesses a better leaving group than 1, the former is less reactive than the latter by a factor of 2 in H2O. This implies that expulsion of the leaving group is not advanced in the rate-determining transition state (TS), i.e., the reactions of 1 and 2 with OH‒ proceed through a stepwise mechanism, in which expulsion of the leaving group from the addition intermediate occurs after the rate-determining step (RDS). Addition of DMSO to H2O would destabilize OH‒ through electronic repulsion between the anion and the negative-dipole end in DMSO. However, destabilization of OH‒ in the ground state (GS) is not solely responsible for the remarkably enhanced reactivity upon addition of DMSO to the medium. The effect of medium on reactivity has been dissected into the GS and TS contributions through combination of the kinetic data with the transfer enthalpies (ΔΔHtr) from H2O to DMSO-H2O mixtures for OH‒ ion.

Kinetic study on the alkaline hydrolysis of Co(NH3)5O2C2Cl32+ and Co(NH3)5O2C2Cl2H2+

1967 ◽  
Vol 6 (2) ◽  
pp. 379-382 ◽  
Author(s):  
Neil S. Angerman ◽  
Robert B. Jordan
Keyword(s):  
Kinetic Study ◽  
Alkaline Hydrolysis ◽  
Hydrolysis Of

scholarly journals Kinetics and Reaction Mechanism for Alkaline Hydrolysis of Y-Substituted-Phenyl Diphenylphosphinates

2013 ◽  
Vol 34 (7) ◽  
pp. 2001-2005 ◽  
Author(s):  
Hyo-Jeong Hong ◽  
Jieun Lee ◽  
Ae Ri Bae ◽  
Ik-Hwan Um
Keyword(s):  
Reaction Mechanism ◽  
Alkaline Hydrolysis ◽  
Hydrolysis Of

Kinetic study of microwave-assisted alkaline hydrolysis of Jatropha curcas oil

2016 ◽  
Author(s):  
Nur’aini Raman Yusuf ◽  
Ruzaimah Nik Mohamad Kamil ◽  
Suzana Yusup
Keyword(s):  
Kinetic Study ◽  
Alkaline Hydrolysis ◽  
Jatropha Curcas ◽  
Jatropha Curcas Oil ◽  
Microwave Assisted ◽  
Hydrolysis Of

Kinetic study on the alkaline hydrolysis of oxalato, fumarato, and maleoto complexes of pentaamminecobalt(III)

1967 ◽  
Vol 6 (7) ◽  
pp. 1376-1379 ◽  
Author(s):  
Neil S. Angerman ◽  
Robert B. Jordan
Keyword(s):  
Kinetic Study ◽  
Alkaline Hydrolysis ◽  
Hydrolysis Of
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