A SURVEY OF THERMODYNAMIC PARAMETERS FOR SOLVOLYSIS IN WATER

1959 ◽  
Vol 37 (4) ◽  
pp. 803-824 ◽  
Author(s):  
R. E. Robertson ◽  
R. L. Heppolette ◽  
J. M. W. Scott
Keyword(s):  
Transition State ◽  
Activation Enthalpy ◽  
Detailed Knowledge ◽  
Standard State ◽  
Initial State ◽  
Enthalpy Of Activation ◽  
Halide Exchange ◽  
Hydrolysis Of Esters ◽  
Hydrolysis Of ◽  
Linear Correlations

A method is suggested for determining the standard state entropies [Formula: see text] of the transition state for the neutral hydrolysis of esters in water. This has required the development of methods for approximating initial state parameters where experimental data are lacking.Characteristic linear correlations between the entropy and enthalpy of activation are observed for hydrolysis in water, as well as for the bimolecular halide exchange reaction in acetone and for acid–base equilibria. Explanations are advanced to explain the observed trends.From the derived standard state entropies, a method for estimating the charge development in the transition state for the methyl and isopropyl halides is proposed. With this further detailed knowledge of the transition state in the methyl halide series, reasonable values of the activation enthalpy can be calculated from available thermochemical data.

Transition state activity coefficients in the acid-catalyzed hydrolysis of esters

1975 ◽  
Vol 97 (18) ◽  
pp. 5223-5231 ◽  
Author(s):  
Robert A. McClelland ◽  
Tomasz A. Modro ◽  
Malcolm F. Goldman ◽  
Keith Yates
Keyword(s):  
Transition State ◽  
Activity Coefficients ◽  
State Activity ◽  
Acid Catalyzed ◽  
Hydrolysis Of Esters ◽  
Hydrolysis Of

scholarly journals Application of Singh-Jha Equation in the Evaluation of b* Parameter of Laidler-Landskroener Equation in the Hydrolysis of Vinyl Acetate

2010 ◽  
Vol 7 (4) ◽  
pp. 1170-1173
Author(s):  
Sangita Sharma ◽  
Bijal Vyas ◽  
Falguni Thakkar ◽  
Ketan Patel ◽  
J. J. Vora
Keyword(s):  
Organic Solvent ◽  
Transition State ◽  
Vinyl Acetate ◽  
Alkaline Hydrolysis ◽  
Initial State ◽  
Closed Approach ◽  
Rate Of Hydrolysis ◽  
Solvent Molecules ◽  
Hydrolysis Of

Singh-Jha method is applied to calculate b* of Laidler-Landskroener equation, the distance of closed approach of solvent molecules to the activated complexes in alkaline hydrolysis of vinyl acetate. This method is applied to alkaline hydrolysis of vinyl acetate in water enriched ethanol between 30 °C and 35 °C. The rate of hydrolysis decreases with the increase of content of organic solvent at both temperatures. The size of transition state was found to be large as compared to the initial state. The b* was found to be 3.7693Å which is in agreement with the values obtained earlier.

Solvolysis of sulphonyl halides. V. Hydrolysis and deuterolysis of methanesulphonyl chloride

1970 ◽  
Vol 23 (12) ◽  
pp. 2427
Author(s):  
ML Tonnet ◽  
AN Hambly
Keyword(s):  
Transition State ◽  
Thermodynamic Parameters ◽  
Isotope Effect ◽  
Large Reduction ◽  
Butyl Chloride ◽  
Solvent Isotope Effect ◽  
Initial State ◽  
Solvent Isotope ◽  
Hydrolysis Of

The values of the thermodynamic parameters of activation have been determined for the solvolysis of methanesulphonyl chloride in H2O and D2O and their mixtures with moderate amounts of dioxan. Some of the data are not in agreement with the postulate that the kinetic solvent isotope effect and the maximum in the rate of solvolysis produced by the addition of dioxan are due to changes in the initial state of the reacting system rather than to changes in the transition state. The addition of dioxan does not produce a large reduction in the solvent isotope effect as reported for the hydrolysis of t-butyl chloride and predicted to be general. The relative rates of solvolysis in mixtures of H2O and D2O are not in agreement with the analysis of such reactions by Swain and Thornton.

Charge Development and Mechanism in Disrotatory Ring Opening of Cyclopropyl Bromides

1974 ◽  
Vol 52 (14) ◽  
pp. 2660-2665 ◽  
Author(s):  
Jan Han Ong ◽  
Ross Elmore Robertson
Keyword(s):  
Transition State ◽  
Temperature Dependence ◽  
Temperature Coefficient ◽  
Isotope Effect ◽  
Ring Opening ◽  
Deuterium Isotope Effect ◽  
Enthalpy Of Activation ◽  
Cis And Trans ◽  
Hydrolysis Of

The temperature dependence of the rates of hydrolysis of cis- and trans-2-vinylcyclopropyl bromides has been determined in water. The temperature coefficient of the enthalpy of activation (ΔCp≠) for both compounds was unusual (−27 and −35 cal mol−1 deg−1). From this fact, it was concluded that the charge development at the transition state was low, in agreement with the conclusions of Clark and Smale (19). The slightly inverse α-deuterium isotope effect (kH/kD = 0.994) is consistent with that conclusion.

Kinetic solvent effects on acid-catalyzed hydrolysis of sucrose in aqueous mixtures of some protic, aprotic, and dipolar aprotic solvents

1986 ◽  
Vol 64 (8) ◽  
pp. 1638-1642 ◽  
Author(s):  
Urmila Mandal ◽  
Kaushik Das ◽  
Kiron Kumar Kundu
Keyword(s):  
Transition State ◽  
Optical Rotation ◽  
Aqueous Mixtures ◽  
Free Energies ◽  
Initial State ◽  
Composition Profiles ◽  
Acid Catalyzed ◽  
Solvent Systems ◽  
Hydrolysis Of ◽  
Reference Electrolyte

Rate constants of acid-catalyzed hydrolysis of sucrose (S) to D-glucose and L-fructose have been determined at 25 °C by optical rotation measurements in aqueous mixtures of protophobic protic glycerol (GL), protophilic protic urea (UH), aprotic dioxane (D), and dipolar aprotic dimethyl sulphoxide (DMSO). Transfer free energies of the substrate sucrose, [Formula: see text] have also been determined in the solvents from solubility measurements. These values as well as those of H+, as obtained earlier by use of the widely used tetraphenylarsonium tetraphenylboron (TATB) reference electrolyte assumption, yielded transfer free energies of the transition state. The observed log (ks/kw) – composition profiles reveal that the rates increase monotonically in GL–water mixtures, that decrease more or less monotonically in UH– and DMSO–water mixtures, and decrease up to 10 mol% D in D–water mixtures, beyond which the values tend to increase. Examination of [Formula: see text]–composition profiles for the different species in each case indicates that the initial and transition state solvation get more or less compensated and the observed rates are dictated by the increased solvation of H+ in aqueous UH, DMSO, and D co-solvent systems. But in GL–water mixtures the decreased solvation of the transition state compared with the initial state is overcome by the decreased solvation of H+, thus resulting in the gradual enhancement of the rates of the reaction. The observed linearity of the correlative plots of −δ(ΔG≠) [= RT ln (ks/kw)] vs. [Formula: see text] with distinctly different slopes in the two cases also substantiates the relative importance of H+ solvation in dictating the rates of the reaction in these widely different aqueous co-solvents.

Ion pairs and heat capacity of activation for 2,2-disubstituted cyclopropyl bromides

1976 ◽  
Vol 54 (8) ◽  
pp. 1246-1252 ◽  
Author(s):  
Surendra Singh ◽  
Ross Elmore Robertson
Keyword(s):  
Heat Capacity ◽  
Transition State ◽  
Relative Rate ◽  
Ion Pairs ◽  
Water Structure ◽  
Ion Pair ◽  
External Effects ◽  
Enthalpy Of Activation ◽  
Rate Ratios ◽  
Hydrolysis Of

The temperature dependence of the rates of hydrolysis of 2,2-dimethylcyclopropyl bromide, 2,2-cis-vinyl-trans-methylcyclopropyl bromide and 2,2-cis-methyl-trans-vinylcyclopropyl bromide have been determined in water. The temperature coefficient of the enthalpy of activation (ΔCp≠) for these compounds was determined to be −52, −27 and −37 cal deg−1 mol−1 respectively. The relative rate ratios for hydrolysis of the 2,2-methylvinylcyclopropyl bromides with respect to the appropriate 2-vinylcyclopropyl bromide isomer indicate a considerable progress towards allyl cations at the transition state in contrast to the indications of the ΔCp≠ values.The ΔCp≠ term for such reactions in water depends to an important degree on the external effects of charge development on water structure but is insensitive to internal electrostatic effects. In the three examples of ΔCp≠ reported in this study, all tend to show small external effects in spite of evidence which might suggest larger. The differences in ΔCp≠ are attributed to the particular shape and charge distribution of the quasi-ion pair.

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