Medium effect on alkaline hydrolysis of diphenic acid monomethyl ester

1980 ◽  
Vol 45 (5) ◽  
pp. 1485-1494 ◽  
Author(s):  
Ján Benko ◽  
Vladislav Holba
Keyword(s):  
Alkaline Hydrolysis ◽  
Reaction Medium ◽  
Activation Parameters ◽  
Butyl Alcohol ◽  
Medium Effect ◽  
Tert Butyl Alcohol ◽  
Diphenic Acid ◽  
Different Temperatures ◽  
Hydrolysis Of ◽  
Monomethyl Ester

The alkaline hydrolysis of diphenic acid monomethyl ester was studied in mixtures of water with methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, tert-butyl alcohol, and acetone. The dependences of the rate constant on the concentration of the nonaqueous component at different temperatures were obtained and the activation parameters at an isodielectric composition of the reaction medium were determined. The influence of the ionic strength on the reaction rate in the mentioned media was studied and conclusions were drawn as to the role of specific interactions between the reacting ions in the kinetics and mechanism of the studied reaction.

Kinetics of alkaline hydrolysis of 3,4-thiophenedicarboxylic acid monomethyl ester in aqueous-nonaqueous media

1988 ◽  
Vol 53 (6) ◽  
pp. 1268-1273
Author(s):  
Ján Benko ◽  
Oľga Vollárová
Keyword(s):  
Methyl Alcohol ◽  
Alkaline Hydrolysis ◽  
Mixed Solvents ◽  
Activation Parameters ◽  
Butyl Alcohol ◽  
Nonaqueous Media ◽  
Alcohol Water ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Monomethyl Ester

The kinetics of alkaline hydrolysis of 3,4-thiophenedicarboxylic acid monomethyl ester has been studied in mixed solvents water-methyl alcohol, water-tert-butyl alcohol, and water-dioxane. The specific effects causing different courses of these dependences have been evaluated. The greatest changes in the thermodynamic activation parameters have been observed in the medium of water-methyl alcohol.

Kinetics of alkaline hydrolysis of diphenic and terephthalic acid monomethyl esters

1980 ◽  
Vol 45 (1) ◽  
pp. 255-262 ◽  
Author(s):  
Vladislav Holba ◽  
Ján Benko ◽  
Jana Kozánková
Keyword(s):  
Ionic Strength ◽  
Alkaline Hydrolysis ◽  
Terephthalic Acid ◽  
Activation Parameters ◽  
Diphenic Acid ◽  
Temperature Dependences ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Specific Influence ◽  
Monomethyl Ester

The dependence of the rate constant of alkaline hydrolysis of diphenic acid monomethyl ester and terephthalic acid monomethyl ester on ionic strength and temperature was studied together with the specific influence of some electrolytes on the reaction rate. Thermodynamic activation parameters extrapolated to zero ionic strength and critical interionic distances of reacting ions were calculated from the temperature dependences of the rate constants.

Effects of organic solvents on immobilized enzyme catalyses. Chymotrypsin immobilized on Sephadex

1980 ◽  
Vol 58 (23) ◽  
pp. 2633-2640 ◽  
Author(s):  
Diana H. Pliura ◽  
J. Bryan Jones
Keyword(s):  
Enzyme Activity ◽  
Organic Solvents ◽  
Immobilized Enzyme ◽  
Reaction Medium ◽  
Butyl Alcohol ◽  
Native Enzyme ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Catalytic Rate ◽  
Hydrolysis Of

The esterolytic activities of native chymotrypsin (CT) and immobilized CT-Sephadex have been studied in the presence of up to 20% of the organic solvents methanol, ethanol, 2-propanol, tert-butyl alcohol, dioxane, or DMSO. The general cosolvent-induced inhibition of the native enzyme was attenuated for immobilized CT. Most noticeably, the apparent catalytic rate constants for the CT-Sephadex-catalyzed hydrolysis of N-acetyl-L-tyrosine ethyl ester were invariant over the 2–20% dioxane concentration range surveyed. In contrast, the activity of the native enzyme in 20% dioxane was only 3% the activity recorded in the absence of cosolvent. Increasing the hydrophobic character of the protic cosolvents destabilized the native enzyme but stabilized CT-Sephadex. Both native and immobilized CT displayed remarkable stability in 20% aqueous DMSO [Formula: see text]. At least part of the DMSO-induced inhibition of native CT and CT-Sephadex was offset by increasing the apparent pH of the reaction medium. The altered kinetic patterns for CT-Sephadex are best explained by the effects of diffusional limitations on the apparent enzyme activity. The best compromise solvent for preparative applications of CT-Sephadex was found to be tert-butyl alcohol.

Kinetics and mechanism of hydrolysis of substituted phenyl N-(4-methylphenyl)sulphonylcarbamates. Solvolysis of 3-nitrophenyl N-(4-methylphenyl)-sulphonylcarbamate in mixtures water-1,4-dioxane and water-tert-butyl alcohol and its decomposition to neutral molecules in non-aqueous media

1979 ◽  
Vol 44 (9) ◽  
pp. 2639-2652 ◽  
Author(s):  
Jitka Moravcová ◽  
Miroslav Večeřa
Keyword(s):  
Organic Solvents ◽  
Ph Dependence ◽  
Aqueous Media ◽  
Activation Parameters ◽  
Butyl Alcohol ◽  
Base Catalysis ◽  
Hydrolysis Rate ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Hydrolysis Of

pH Dependence of hydrolysis rate of the substituted phenyl N-(4-methylphenyl)sulphonylcarbamates has been followed in aqueous medium. The activation parameters and the Hammet reaction constant (ρ = 2.4) have been determined at pH 11.3. For hydrolysis of 3-nitrophenyl N-(4-methylphenyl)sulphonylcarbamate (pK about 3.5) no general base catalysis has been found. The hydrolysis mechanism is discussed. Perturbation of the water structure by organic solvents (1,4-dioxane and tert-butyl alcohol) has been used for differentiation of ElcB and Bac2 mechanisms, 2,4-dinitrophenyl acetate being used for comparison. The decomposition rates of 3-nitrophenyl N(4-methylphenyl)sulphonylcarbamate have been determined in six organic solvents. Mechanism of spontaneous splitting of the carbamate molecule in non-aqueous media is discussed.

Alkaline hydrolysis of methyl hydrogen malonate in water-organic solvents

1986 ◽  
Vol 51 (6) ◽  
pp. 1187-1194 ◽  
Author(s):  
Oľga Grančičová ◽  
Vladislav Holba ◽  
Ľudmila Beluská
Keyword(s):  
Experimental Data ◽  
Ethylene Glycol ◽  
Alkaline Hydrolysis ◽  
Transfer Functions ◽  
Butyl Alcohol ◽  
Gibbs Energies ◽  
Tert Butyl Alcohol ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Activated Complex

Kinetics of alkaline hydrolysis of methyl hydrogen malonate in water-methanol, water-dioxane, water-tert-butyl alcohol and water-ethylene glycol mixtures was examined. The valuse of the transfer functions of the activated complex δmμ≠ from water to the first two mixed media were calculated from the measured solubilities of tetrabutylammonium hydrogen malonate, the activation Gibbs energies and the known values of transfer functions for tetrabutylammonium and hydroxide ions. Some conclusions concerning the effect of a nonaqueous component of the solvent on solvation of the reactants and the activated complex have been drawn from the experimental data obtained.

Thermodynamic and Kinetic Investigation of the Solvent Effect on the Oxidation of [Co(en)2SCH2COO]+ with S2O82- In Water-Methanol and Water-tert-Butyl Alcohol Mixtures

1993 ◽  
Vol 58 (5) ◽  
pp. 1001-1006 ◽  
Author(s):  
Oľga Vollárová ◽  
Ján Benko
Keyword(s):  
Transfer Functions ◽  
Activation Parameters ◽  
Butyl Alcohol ◽  
Oxidation Of Co ◽  
Kinetics Of Oxidation ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Alcohol Mixtures ◽  
Kinetics Of

The kinetics of oxidation of [Co(en)2SCH2COO]+ with S2O82- was studied in water-methanol and water-tert-butyl alcohol mixtures. Changes in the reaction activation parameters ∆H≠ and ∆S≠ with varying concentration of the co-solvent depend on the kind of the latter, which points to a significant role of salvation effects. The solvation effect on the reaction is discussed based on a comparison of the transfer functions ∆Ht0, ∆St0 and ∆Gt0 for the initial and transition states with the changes in the activation parameters accompanying changes in the CO-solvent concentration. The transfer enthalpies of the reactant were obtained from calorimetric measurements.

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.

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