Solvolysis of isopropyl bromide in ethanol–water mixtures. Dissection into initial state and transition state contributions

1976 ◽  
Vol 54 (24) ◽  
pp. 3944-3948 ◽  
Author(s):  
Wiendelt Drenth ◽  
Michael Cocivera
Keyword(s):  
Vapor Pressure ◽  
Transition State ◽  
Thermodynamic Parameters ◽  
Activation Parameters ◽  
Solvent Composition ◽  
Initial State ◽  
Partial Vapor Pressure ◽  
State Variation

Rates were determined for the solvolysis of isopropyl bromide in ethanol–water mixtures (20 to 80% by volume of ethanol) at 50 and 75 °C and the corresponding activation parameters calculated. From the partial vapor pressure of isopropyl bromide over the various solutions at 50 and 75 °C, the variations in its initial state thermodynamic parameters were calculated. Thus, the variation in the activation parameters with solvent composition could be analyzed in terms of initial and transition state contributions. The initial state variation dominates according to a unimolecular as well as to a bimolecular treatment of data.

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.

The pressure dependence of benzyl chloride solvolysis in aqueous acetone and aqueous dimethylsulfoxide

1970 ◽  
Vol 48 (16) ◽  
pp. 2494-2499 ◽  
Author(s):  
Digby D. Macdonald ◽  
J. B. Hyne
Keyword(s):  
Transition State ◽  
Benzyl Chloride ◽  
Activation Volume ◽  
Aqueous Acetone ◽  
Solvent Composition ◽  
Pressure Data ◽  
Initial State ◽  
First Order ◽  
Solvent Systems ◽  
Aqueous Dimethylsulfoxide

First-order rate constants for the solvolysis of benzyl chloride in a series of aqueous acetone and aqueous dimethylsulfoxide (DMSO) mixtures at 50.100 °C and at various pressures in the range 1–4083 atm are reported. Volume of activation, calculated from the rate/pressure data, is found to exhibit extremum behavior with varying solvent composition in both solvent systems. The activation volumes are dissected into their initial state and transition state contributions by determining the "instantaneous" volumes of solution of benzyl chloride in the solvent systems. The contributions of both the initial state and the transition state to the behavior of the activation volume as a function of solvent composition are discussed.

Kinetics and Mechanism of the 2+ 2 Cycloaddition of Tetracyanoethylene to 2,5-Dimethyl-2,4-Hexadiene

1988 ◽  
Vol 43 (5) ◽  
pp. 435-441 ◽  
Author(s):  
Adel N. Asaad ◽  
Gunnar Aksnes
Keyword(s):  
Complex Formation ◽  
Transition State ◽  
Thermodynamic Parameters ◽  
Cycloaddition Reaction ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Kinetics And Mechanism ◽  
Eda Complex ◽  
Kinetics Of ◽  
Cyclobutane Derivative

The kinetics of the 2 + 2 cycloaddition reaction between tetracyanoethylene and 2,5-dimethyl- 2,4-hexadiene in different solvents has been studied by following the disappearance of the intermediate EDA-complex spectrophotometrically. It is concluded that the EDA-complex is transformed through a concerted cyclicpolar transition state to give the vinyl cyclobutane derivative (III). The effects of various solvents on the reaction rates have been analysed using a multiparameter approach. The thermodynamic parameters (ΔH0 and ΔS0), of EDA-complex formation and the activation parameters (ΔH# and ΔS#) of the cycloaddition have been discussed.

The Mutarotation of Glucose in Dimethylsulfoxide and Water Mixtures

1973 ◽  
Vol 51 (4) ◽  
pp. 556-564 ◽  
Author(s):  
N. M. Ballash ◽  
E. B. Robertson
Keyword(s):  
Transition State ◽  
Activation Parameters ◽  
Solvent Composition ◽  
Water Molecules ◽  
Solvent Mixtures ◽  
Cyclic Transition ◽  
Proton Transfers ◽  
Poor Region ◽  
Cyclic Transition State ◽  
Acid Catalyzed

The mutarotation of glucose is a general acid – base-catalyzed reaction which involves two proton transfers. Whether these proton transfers are carried out in a stepwise or concerted manner, the latter alternative possibly incorporating several water molecules in a cyclic transition state, is not known with certainty.This study was undertaken in an attempt to clarify the mechanism by determining directly the number of water molecules participating in the transition state. The method chosen was to determine rates for the acid-catalyzed mutarotation of glucose as a function of solvent composition in dimethylsulfoxide and water mixtures, particularly in the water poor region. The results show that for the acid-catalyzed reaction the order with respect to water is zero. For water catalysis, the results are less reliable but suggest that about three water molecules may be involved. These facts are interpreted to mean that a stepwise mechanism is operative in the proton-catalyzed reaction, but that the solvent-catalyzed process may involve a cyclic concerted mechanism.Rate measurements were also carried out as a function of temperature for various solvent mixtures. The calculated activation parameters remain practically constant over the solvent composition region and attest to the constancy of the mechanism over this range. Thus the results which pertain strictly to solutions of high dimethylsulfoxide content should apply to aqueous solutions as well.

Solvent effect on the initial state and transition state of anation of pentaammine-aquachromium(III) ion by thiocyanate

1993 ◽  
Vol 18 (1) ◽  
pp. 110-112 ◽  
Author(s):  
Olga A. ◽  
J�n Benko ◽  
Ol'ga Voll�rov� ◽  
Vladislav Holba
Keyword(s):  
Transition State ◽  
Solvent Effect ◽  
Initial State

scholarly journals PHYSICAL CHEMICAL STUDIES OF THE SURFACTANT DILAURYLDIMETHYLAMMONIUM BROMIDE (DLDMAB): AGGREGATION AND CATALYTIC PROPERTIES

2009 ◽  
Vol 17 (17) ◽  
pp. 21-32
Author(s):  
Elizabeth Fatima de Souza ◽  
Silvia Dani ◽  
Lavinel G. IONESCU
Keyword(s):  
Thermodynamic Parameters ◽  
Catalytic Properties ◽  
Activation Parameters ◽  
Critical Micellar Concentration ◽  
Physical Chemical ◽  
Chemical Studies ◽  
Diphenyl Phosphate ◽  
C 32 ◽  
Free Energy Of Micellization ◽  
Hydrolysis Of

The micellization of dilauryldimethylammonium bromide (DLDMAB) in water was studied by using surface tension measurements. The critical micellar concentration (CMC) was determined at 25°C, 32°C and 40°C and thermodynamic parameters such as the free energy of micellization (∆G°mic), enthalpy (∆H°mic), and entropy (∆S°mic) of micellization were measured. The CMC at 25°C was 4.93 x 10-5 M and the corresponding values of the thermodynamic parameters were: ∆G°mic = -5.87 kcal/mol; ∆H°mic = -1.12 kcal/mol and ∆S°mic = +16.00 e.u. Micelles of the surfactant DLDMAB act as catalysts for the alkaline hydrolysis of p-nitrophenyl diphenyl phosphate (NPDPP) with a maximum catalytic factor of approximately 120 compared to 80 for CTAB. Typical activation parameters measured for 1.00 x 10-3 M surfactant and 0.005 M NaOH were: Ea = 9.7 kcal/mo/; ∆H°≠ = 9.1 kcal/mol; ∆G°≠ = 19.6 kcal/mol and ∆S°≠ = -33.9 e.u. The kinetic results were also analyzed in terms of the pseudo-phase ion-exchange models (PPIE) and showed that the model is applicable to describe the experimental results.

Isotope effects and activation parameters for the proton transfer reaction from 1-(4-nitrophenyl)-1-nitroethane to free anions and ion pairs of cesium n-propoxide in n-propanol solvent

1986 ◽  
Vol 64 (6) ◽  
pp. 1021-1025 ◽  
Author(s):  
Arnold Jarczewski ◽  
Grzegorz Schroeder ◽  
Przemyslaw Pruszynski ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Rate Constants ◽  
Isotope Effects ◽  
Ion Pairs ◽  
Activation Parameters ◽  
Solvation Shell ◽  
Ion Pair ◽  
Initial State ◽  
Free Ion ◽  
Deuteron Transfer

Rate constants for the proton and deuteron transfer from 1-(4-nitrophenyl)-1-nitroethane to cesium n-propoxide in n-propanol have been measured under pseudo-first-order conditions with an excess of base for four temperatures between 5 and 35 °C. Using literature values of the fraction of cesium n-propoxide ion pairs that are dissociated into free ions, separate second-order rate constants for the proton and deuteron transfer to the ion pair and to the free ion have been calculated. The cesium n-propoxide ion pair is about 2.8 times more reactive than the free n-propoxide ion. The primary kinetic isotope effects for the two reactions are the same (kH/kD = 6.1–6.3 at 25 °C) within experimental error. The enthalpy of activation is smaller for the ion-pair reaction and the entropy of activation more negative than for the free-ion reaction. For proton transfer, ΔH±ion pair = 8.3 ± 0.2 kcal mol−1, ΔH±ion = 9.6 ± 1.0 kcal mol−1, ΔS±ion pair = −12.3 ± 0.6 cal mol−1 deg−1, ΔS±ion = −10.1 ± 3.4 cal mol−1 deg−1. The greater reactivity of the ion pair relative to the free ion is interpreted in terms of the weaker solvation shell of the ion pair in the initial state.

Initial state and transition state contributions to solvent effects on activation enthalpies for substitution reactions of tris(1,10-phenanthroline)iron(II) in aqueous methanol

1983 ◽  
Vol 8 (3) ◽  
pp. 148-152 ◽  
Author(s):  
Michael J. Blandamer ◽  
John Burgess ◽  
Timothy Digman ◽  
Philip P. Duce ◽  
John P. McCann ◽  
...  
Keyword(s):  
Transition State ◽  
Solvent Effects ◽  
Aqueous Methanol ◽  
Substitution Reactions ◽  
Initial State
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