Kinetics of neutral hydrolysis of two 1-acyl-1,2,4-triazoles in binary aqueous mixtures: a critique of the Evans and Polanyi proposals concerning isochoric activation parameters

1985 ◽  
Vol 107 (21) ◽  
pp. 6031-6035 ◽  
Author(s):  
Jan R. Haak ◽  
Jan B. F. N. Engberts ◽  
Michael J. Blandamer
Keyword(s):  
Activation Parameters ◽  
Aqueous Mixtures ◽  
Kinetics Of ◽  
Hydrolysis Of

Kinetics of the hydrolysis of acyl chlorides in pure water

1967 ◽  
Vol 45 (14) ◽  
pp. 1619-1629 ◽  
Author(s):  
A. Queen
Keyword(s):  
Pure Water ◽  
Activation Parameters ◽  
Acyl Chlorides ◽  
Reversible Addition ◽  
Electron Donation ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Chlorine Bond ◽  
Oxygen Bond ◽  
Bimolecular Mechanism

The activation parameters ΔH≠, ΔS≠, and ΔCP≠ for the hydrolyses of a series of alkyl chloroformates and dimethylcarbamyl chloride in water have been determined. The results indicate that, with increasing electron donation to the chlorocarbonyl group, the mechanism changes from bimolecular to unimolecular (SN1) displacement at this position. For isopropyl chloroformate, some concurrent alkyl–oxygen bond fission is also indicated. The bimolecular mechanism involves reversible addition of water to the carbonyl group followed by ionization of the carbon–chlorine bond.

Synthesis and Base Hydrolysis of the Pentaammine(dimethyl sulfide)cobalt(III) Ion

1992 ◽  
Vol 45 (12) ◽  
pp. 2049 ◽  
Author(s):  
A Ellis ◽  
A Fultz ◽  
R Hicks ◽  
T Morgan ◽  
L Parsons ◽  
...  
Keyword(s):  
Linear Dependence ◽  
Reaction Rate ◽  
Dimethyl Sulfide ◽  
Activation Parameters ◽  
Base Hydrolysis ◽  
Basic Solution ◽  
Acidic Solutions ◽  
Temperature Range ◽  
Kinetics Of ◽  
Hydrolysis Of

The synthesis of the trifluoromethanesulfonate salt of the pentaarnmine (dimethy1 sulfide)-cobalt(III) ion, [NH3)5Co-S(CH3)2]3+, is described along with the kinetics of its hydrolysis in basic and acidic solutions. The synthesis proceeds in 44% yield from the reaction of [(NH3)5Co-OSO2CF3] (CF3SO3)2 with CH3SCH3 in tetramethylene sulfone at 80�C. The salt has been characterized by elemental analysis, visible-U.V. spectroscopy, and 1H n.m.r. In basic solution the complex decomposes by Co-S cleavage to yield [(NH3)5CO-OH]2+ and non-coordinated CH3SCH3. The kinetics of this reaction were studied in phosphate buffers ranging from pH 8.50 to 11.67 ( �= 1.0 M); a linear dependence of the reaction rate on [OH-] was observed. At 25�C, kOH = 8.8 � 0.2 dm3 mol-1 s-1. Activation parameters, determined over a temperature range from 15 to 44�C, were ΔH‡ = 152 � 3 kJ mol-1 and Δ S‡ = 286 � 9 J K-1 mol-1. In 0.01 M HClO4 ( � = 1.0 M, 25�C), the cobaltsulfur bond is cleaved at a rate of 1.6×10-6 s-l. Activation parameters, determined over a temperature range from 25 to 60�C, were ΔH‡ = 106 � 5 kJ mol-1 and ΔS‡= -2 � 16 J K-1 mol-1.

Medium effects on activation parameters on alkaline hydrolysis of 2-carbomethoxypropionate ion in aqueous mixtures of ethylene glycol

1987 ◽  
Vol 65 (2) ◽  
pp. 235-237 ◽  
Author(s):  
Prasanta Kumar Biswas ◽  
Bikas Chandra Bag ◽  
Mihir Nath Das
Keyword(s):  
Ethylene Glycol ◽  
Alkaline Hydrolysis ◽  
Silver Salt ◽  
Activation Parameters ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Medium Effects ◽  
Transfer Parameters ◽  
Experimental Values ◽  
Hydrolysis Of

The standard free energies of transfer [Formula: see text] of the 2-carbomethoxypropionate ion (R−) have been determined from the solubilities of the silver salt (AgR) in water and six aqueous mixtures of ethylene glycol (1–60%) at 25 °C, using the literature values of [Formula: see text] of Ag+. Utilizing these values of the R− ion as well as the literature values of [Formula: see text] of the OH− ion, combined with the experimental values of ΔG≠ for the alkaline hydrolysis of R− ion, the corresponding transfer parameters of the transition states [Formula: see text] for the hydrolysis reaction in aquo-glycolic media at 25 °C have been calculated. Attempts have been made to correlate the rates and activation parameters with the transfer quantities and solvent properties.

Kinetics of the hydrolysis of thiochloroformate esters in pure water

1970 ◽  
Vol 48 (4) ◽  
pp. 522-527 ◽  
Author(s):  
A. Queen ◽  
T. A. Nour ◽  
M. N. Paddon-Row ◽  
K. Preston
Keyword(s):  
Isotope Effect ◽  
Structural Changes ◽  
Pure Water ◽  
Activation Parameters ◽  
Deuterium Isotope Effect ◽  
Hydro Carbon ◽  
Electron Donation ◽  
Kinetics Of ◽  
Hydrolysis Of

The effects of structural changes on the rates of hydrolysis of a series of thiochloroformate esters in water have been investigated. The reactivity is enhanced by increased electron donation by the hydro carbon group. These results, the activation parameters for the hydrolysis of methyl thiochloroformate and the solvent deuterium isotope effect, are shown to be consistent with the operation of the SN1 mechanism.

Kinetics of aquation and base hydrolysis of the macrocyclic complex trans-Bromo(N-meso-5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)nitro-cobalt(III) perchlorate

1976 ◽  
Vol 29 (10) ◽  
pp. 2319 ◽  
Author(s):  
GA Lawrance ◽  
RW Hay
Keyword(s):  
Activation Parameters ◽  
Macrocyclic Complex ◽  
Base Hydrolysis ◽  
Hydrolysis Kinetics ◽  
Rate Expression ◽  
Entropy Of Activation ◽  
Ph Range ◽  
Kinetics Of ◽  
Hydrolysis Of

The macrocyclic complex trans-[Co(dtcd)(NO2)Br] [ClO4] (dtcd = 5,12-dimethyl-l,4,8,1l-tetraaza-cyclotetradeca-4,ll-diene) has been prepared and its hydrolysis kinetics investigated. At 25�C and 0.1 M HN03 the aquation occurs with kaq = 6.2 x 10-3 s-1 to give the trans-Co(dtcd)(NO2)- (OH2)]2+ cation. The activation parameters at 298 K are ΔH? = 75.0 kJ mol-1 and ΔS? = -35.6 J K-1 mol-1. Hydrolysis of the bromide in the pH range 7.5-8.8 follows the rate expression kobs = kaq + kOH[OH-]. At 25�C (I = 0.1 M, NaClO4) kOH = 1.21 x 103 1. mol-1 s-1 with the activation parameters for base hydrolysis being ΔH? = 74.2 kJ mol-1 and ΔS? = +63.2 J K-1 mol-1 at 298 K. Aquation and base hydrolysis of the bromo complex at 25�C occur at rates 14 and 5 times faster respectively than those previously reported for the analogous trans-[Co(dtcd)(NO2)Cl]+ complex, the acceleration being due to a more favourable entropy of activation in each case.

Kinetics of alkaline hydrolysis of mono- and dimethyl esters of 2,3- and 3,4-thiophenedicarboxylic acids, cyanothiophenecarboxylic acids and their dihydroanalogues

1987 ◽  
Vol 52 (8) ◽  
pp. 2005-2018
Author(s):  
Milan Struhárik ◽  
Pavel Hrnčiar ◽  
Dušan Loos
Keyword(s):  
Kinetic Parameters ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Activation Parameters ◽  
Hydrolysis Rate ◽  
Electronic Effects ◽  
Cyclic System ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Reactivity Order

Kinetics of alkaline hydrolysis of mono- and dimethyl esters of 2,3- and 3,4-thiophenedicarboxylic acids and their dihydroanalogues have been studied in 70% dioxane. The rate measurements have been carried out by the titrimetric method and the k1, k2 rate constants evaluated by the Frost-Schwemer method. The activation parameters of these reactions have been calculated. The results are compared with kinetic parameters of alkaline hydrolysis of methyl and dimethyl phthalates. The hydrolysis rate is significantly affected by the cyclic system to which the methoxycarbonyl groups are bound, the reactivity order being: Dihydrothiophene > thiophene > benzene. Also measured were the kinetics of alkaline hydrolyses of methyl 4-cyano-3-thiophenecarboxylate and 3-cyano-2-thiophenecarboxylate and of their dihydroanalogues. No meaningful preference of the hydrolysis of the group at the position 2 has been observed in case of 2,3-isomers. However, it has been confirmed that the hyper- and hypo-ortho transfer of electronic effects operates in the thiophene nucleus.

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.

scholarly journals Kinetics of base hydrolysis of α-amino acid esters catalyzed by palladium(II) piperazine complex

2010 ◽  
Vol 8 (4) ◽  
pp. 797-805 ◽  
Author(s):  
Azza Shoukry ◽  
Mohamed Shoukry ◽  
Mohamed Hafez
Keyword(s):  
Kinetic Data ◽  
Methyl Esters ◽  
Activation Parameters ◽  
Base Hydrolysis ◽  
Amino Acid Esters ◽  
One Step ◽  
Glycine Methyl Ester ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Acid Esters

AbstractThe kinetics of base hydrolysis of glycine, histidine, and methionine methyl esters in the presence of [Pd(pip)(H2O)2]2+ complex, where pip is piperazine, is studied in aqueous solutions, at T = 25°C, and I = 0.1 mol dm−3. The rate of ester hydrolysis for glycine methyl ester is studied at different temperature and dioxane/water solutions of different compositions. The kinetic data are fit under the assumption that the hydrolysis proceeds in one step. The activation parameters for the base hydrolysis of the complexes are evaluated

Sign in / Sign up

Export Citation Format

Share Document