Kinetic medium effects. II. Hydrolysis of esters in electrolyte solutions

1965 ◽  
Vol 18 (12) ◽  
pp. 1943 ◽  
Author(s):  
PT McTigue ◽  
AR Watkins
Keyword(s):  
Rate Constants ◽  
Butyl Acetate ◽  
Aqueous Electrolyte ◽  
Aqueous Media ◽  
Electrolyte Solutions ◽  
Hydration Numbers ◽  
Medium Effects ◽  
Hydrolysis Of Esters ◽  
Hydrolysis Of ◽  
Methyl Chloroacetate

Rate constants have been measured for the acid-catalysed hydrolyses of t-butyl acetate and methyl chloroacetate in various aqueous electrolyte solutions; the activity coefficients of the esters in these electrolyte solutions have also been measured. The results are used to test a recently proposed method of determining transition state hydration numbers for reactions in aqueous media.

NMR Studies of Aqueous Electrolyte Solutions. IV. Hydration Numbers of Strong Electrolytes Determined from Temperature Effects on Proton Shifts

1971 ◽  
Vol 54 (1) ◽  
pp. 178-181 ◽  
Author(s):  
Brother Ferdinand J. Vogrin ◽  
Paul S. Knapp ◽  
William L. Flint ◽  
Arthur Anton ◽  
Gerald Highberger ◽  
...  
Keyword(s):  
Temperature Effects ◽  
Aqueous Electrolyte ◽  
Electrolyte Solutions ◽  
Hydration Numbers ◽  
Nmr Studies ◽  
Aqueous Electrolyte Solutions ◽  
Strong Electrolytes

scholarly journals Effect of Anions (Cl−, SO2−4) on the Interfacial Properties of Akaganeite (β-FeOOH) in Aqueous Electrolyte Solutions

1988 ◽  
Vol 5 (4) ◽  
pp. 257-279 ◽  
Author(s):  
K.M. Parida
Keyword(s):  
Aqueous Electrolyte ◽  
Surface Acidity ◽  
Aqueous Media ◽  
Electrolyte Solutions ◽  
Chloride Ions ◽  
Point Of Zero Charge ◽  
Surface Complexes ◽  
Solution Interface ◽  
Adsorption Data ◽  
Titration Data

The point of zero charge (pHpzc) of the sample (β-FeOOH) is shifted from 7.50 to 8.20 and 8.55, respectively, in KCl and K2SO4 electrolyte media. Intrinsic surface acidity and complexation constants have been calculated by single and double extrapolation methods using Potentiometrie titration data obtained for different concentrations of KCl and K2SO4 in aqueous media. Complexation con stants for K+, Cl− and SO2−4 have also been calculated from adsorption data by the same two methods. Close agreement exists between the two sets of values. Chloride ions form SOH2−4 – Cl− surface complexes on a β-FeOOH surface, whereas sulphate ions form two types of surface complex i.e. SOH+2 – SO2−4 and SOH+2 – SO4H−. Various parameters such as σ0, ψ0, ψd, dσ0/dψ0, etc. associated with the electrical double layer at the oxide/aqueous KCl and K2SO4 electrolyte solution interface have been calculated from Potentiometrie and adsorption data, and are discussed.

Interpretation of properties of aqueous electrolyte solutions in terms of hydration and incomplete dissociation

1988 ◽  
Vol 53 (4) ◽  
pp. 686-696 ◽  
Author(s):  
Rajalakshmi Heyrovská
Keyword(s):  
Aqueous Solutions ◽  
Aqueous Electrolyte ◽  
Electrolyte Solutions ◽  
Hydration Numbers ◽  
Concentrated Aqueous Solutions ◽  
Strong Electrolytes ◽  
Strong Acids ◽  
Degrees Of Dissociation ◽  
Concentration Cells ◽  
Existing Data

The existing data on the vapour pressures, densities and e.m.f.s of concentration cells of dilute and concentrated aqueous solutions of strong electrolytes have been interpreted in terms of hydration and incomplete dissociation. Hydration numbers and degrees of dissociation have been presented for several 1 : 1 strong electrolytes at 25 °C. Thus the actual ionic concentrations of strong acids, bases and salts, hitherto inaccessible, have now been made available.

Influence of the Polarity of the Medium on the Alkaline Hydrolysis of n-Butyl Acetate in Hydroalcoholic Mixtures

1977 ◽  
Vol 32 (5) ◽  
pp. 496-500
Author(s):  
M. S. Celdrán ◽  
M. V. Ramón ◽  
P. Martínez
Keyword(s):  
Reaction Mechanism ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Butyl Acetate ◽  
Activation Energies ◽  
Free Energies ◽  
Kinetics Of ◽  
Hydrolysis Of

Abstract The kinetics of the alkaline hydrolysis of n-butyl acetate have been studied in water and in hydroalcoholic mixtures. The rate constants, activation energies, frequency factors, entropies, Gibbs free energies and enthalpies of activation have been determined. The radii of the activated com­ plexes have been calculated and related to their degree of solvation. A possible reaction mechanism is formulated.

Hydrolysis of esters of oxy acids: pKa values for strong acids; Brønsted relationship for attack of water at methyl; free energies of hydrolysis of esters of oxy acids; and a linear relationship between free energy of hydrolysis and pKa holding over a range of 20 pK units

1978 ◽  
Vol 56 (17) ◽  
pp. 2342-2354 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Rate Constants ◽  
Methyl Esters ◽  
Dimethyl Sulfate ◽  
Tetraethyl Orthosilicate ◽  
Free Energies ◽  
Dilute Aqueous Solution ◽  
Hydrolysis Of Esters ◽  
Strong Acids ◽  
Hydrolysis Of ◽  
Good Agreement

By combining various kinds of evidence from the literature it is possible to derive an internally consistent set of pKa values for the strong mineral acids and the arenesulfonic acids; the values are referred to dilute aqueous solution as standard state and are expected to be correct within 0.5 log unit. Using these pKa values and literature data for hydrolysis of methyl esters of acids of the type Y—XO3Men, where Y is O, OH, OMe, alkyl, or aryl and X is Cl, S, or P, a Brønsted plot can be constructed with slope equal to 1.02 ± 0.04. From the free energies of hydrolysis for dimethyl sulfate and the methyl phosphates it is possible to calculate rate constants for the microscopic reverse reaction. These define a Brønsted line of slope 0.27 ± 0.3, from which rate constants for the formation of the esters of perchloric and various sulfonic acids may be estimated. This permits calculation of free energies of hydrolysis for these esters.Thermochemical data in the literature permit calculation of the free energies of hydrolysis of dimethyl sulfate, trimethyl arsenite, and tetraethyl orthosilicate. In the case of dimethyl sulfate the calculation (using the previously reported eq. [1]) leads to a pKa value in close agreement with theoretical expectation, confirming that eq. [1] is valid for acids of pKa ≥ −3. For tetraethyl orthosilicate the thermochemical data are less precise but are in satisfactory agreement with the predictions of eq. [1]. The free energies of hydrolysis derived from the Brønsted correlations are also in good agreement with expectation based on eq. [1].For acids where resonance phenomena are important either in the acid itself (boric acid) or in the anion (nitric acid, nitrous acid, carboxylic acids) the experimental free energies of formation fall far from the line defined by eq. [1]. It is concluded that eq. [1] is limited to species where there is no n delocalization involving the reacting oxygen, but where this condition is satisfied, the equation holds over the entire accessible range of oxy acid pKa values, i.e., from −6.4 to 16.

Kinetics and Mechanisms of the Acid-catalysed Hydrolysis of Tertiary Butyl Acetate

1962 ◽  
Vol 15 (3) ◽  
pp. 467 ◽  
Author(s):  
KR Adam ◽  
I Lauder ◽  
VR Stimson
Keyword(s):  
Rate Constants ◽  
Butyl Acetate ◽  
Arrhenius Equation ◽  
Aqueous Acetone ◽  
Energy Of Activation ◽  
Kcal Mole ◽  
Tertiary Butyl ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of the acid-catalysed hydrolysis of tertiary butyl acetate in water, in aqueous acetone, and in aqueous dioxan, over a range of temperature have been studied. The Arrhenius equation is not obeyed. In 40% water-60% acetone the energy of activation varies from 26-29 kcal mole-1 for temperatures 48-97 �C. This is due presumably to simultaneous hydrolyses via the AAL1 and the AAC2 mechanisms. By combination of oxygen-18 tracer results and kinetic results the rate constants for reactions by these mechanisms in water have been separated. The observed percentage of alkyl-oxygen fission in water varies from 85 at 25 �C to 97 at 60 �C. Rate constants for reactions by the AAL1 and the AAC2 mechanisms are expressed by the equations : k (sec-1 l mole-1) = 10l6.l exp (-27500/RT), and k (sec-1 l mole-1) = 107.9 exp (-l73OO/RT),respectively. However, the parameters of the latter equation may contain considerable errors because the extent of reaction by the AAC2 mechanism is small. In water and in 80% water-20% acetone, tertiary butyl acetate undergoes an uncatalysed solvolytic reaction, involving presumably the BAL1 mechanism. The variation of the rate of this reaction with temperature is expressed by the equation, k (sec-1) = 1012.3 exp (-26800/RT).

The Effects of Amines on the Esterase Activities of Thrombin and Thrombokinase and on Several Clotting Tests

1974 ◽  
Vol 31 (02) ◽  
pp. 309-318
Author(s):  
Phyllis S Roberts ◽  
Raphael M Ottenbrite ◽  
Patricia B Fleming ◽  
James Wigand
Keyword(s):  
Choline Chloride ◽  
Polymerization Process ◽  
Ammonium Bromide ◽  
Bovine Thrombin ◽  
One Stage ◽  
Human Proteins ◽  
Rate Of Hydrolysis ◽  
The One ◽  
Hydrolysis Of Esters ◽  
Hydrolysis Of

Summary1. Choline chloride, 0.1 M (in 0.25 M Tris. HCl buffer, pH 7.4 or 8.0, 37°), doubles the rate of hydrolysis of TAME by bovine thrombokinase but has no effect on the hydrolysis of this ester by either human or bovine thrombin. Only when 1.0 M or more choline chloride is present is the hydrolysis of BAME by thrombokinase or thrombin weakly inhibited. Evidence is presented that shows that these effects are due to the quaternary amine group.2. Tetramethyl ammonium bromide or chloride has about the same effects on the hydrolysis of esters by these enzymes as does choline chloride but tetra-ethyl, -n.propyl and -n.butyl ammonium bromides (0.1 M) are stronger accelerators of the thrombokinase-TAME reaction and they also accelerate, but to a lesser degree, the thrombin-TAME reaction. In addition, they inhibit the hydrolysis of BAME by both enzymes. Their effects on these reactions, however, do not follow any regular order. The tetraethyl compound is the strongest accelerator of the thrombokinase-TAME reaction but the tetra-ethyl and -butyl compounds are the strongest accelerators of the thrombin-TAME reaction. The ethyl and propyl compounds are the best (although weak) inhibitors of the thrombokinase-BAME and the propyl compound of the thrombin-BAME reactions.3. Tetra-methyl, -ethyl, -n.propyl and -n.butyl ammonium bromides (0.01 M) inhibit the clotting of fibrinogen by thrombin (bovine and human proteins) at pH 7.4, imidazole or pH 6.1, phosphate buffers and they also inhibit, but to a lesser degree, a modified one-stage prothrombin test. In all cases the inhibition increases regularly as the size of the alkyl group increases from methyl to butyl. Only the ethyl com pound (0.025 M but not 0.01 M), however, significantly inhibits the polymerization of bovine fibrin monomers. It was concluded that inhibition of the fibrinogen-thrombin and the one-stage tests by the quaternary amines is not due to any effect of the com pounds on the polymerization process but probably due to inhibition of thrombin’s action on fibrinogen by the quaternary amines.

Promoting Nitrogen Electroreduction to Ammonia with Bismuth Nanocrystals and Potassium Cations in Water

2020 ◽  
Author(s):  
Jaecheol Choi ◽  
Hoang-Long Du ◽  
Manjunath Chatti ◽  
Bryan H. R. Suryanto ◽  
Alexandr Simonov ◽  
...  
Keyword(s):  
Electrocatalytic Activity ◽  
Aqueous Electrolyte ◽  
Electrolyte Solutions ◽  
Reduction Reaction ◽  
Nitrogen Reduction ◽  
Aqueous Electrolyte Solutions

We demonstrate that bismuth exhibits no measurable electrocatalytic activity for the nitrogen reduction reaction to ammonia in aqueous electrolyte solutions, contrary to several recent reports on the highly impressive rates of Bi-catalysed electrosynthesis of NH<sub>3</sub> from N<sub>2</sub>.

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