REACTIONS OF SULPHONIC ESTERS: VI. THE TEMPERATURE DEPENDENCE OF THE RATE FOR THE HYDROLYSIS OF A SERIES OF ALKYL BENZENESULPHONATES

1957 ◽  
Vol 35 (7) ◽  
pp. 613-622 ◽  
Author(s):  
R. E. Robertson
Keyword(s):  
Transition State ◽  
Temperature Dependence ◽  
Methyl Ethyl ◽  
Temperature Dependent ◽  
Temperature Coefficients ◽  
Nucleophilic Displacement ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

Data are presented showing temperature dependence of the rate of hydrolysis of methyl, ethyl, isopropyl, and n-propyl benzenesulphonates in water. The heat of activation is shown to be temperature dependent to the extent of −30 to −40 cal./mole deg. Since, in solvolysis, the properties of water favor ionization over nucleophilic displacement, it is suggested that these temperature coefficients, ΔCp‡, and the accompanying entropy differences, ΔS‡, can be rationalized in terms of variations in the reorganization of the solvent about the transition state.

The Nucleophilic Displacement of the Nitrate Group. 1. The Hydrolysis of a Series of Benzyl Nitrates in Water

1974 ◽  
Vol 52 (13) ◽  
pp. 2485-2490 ◽  
Author(s):  
Kalavelil Matthew Koshy ◽  
Ross Elmore Robertson
Keyword(s):  
Individual Differences ◽  
Transition State ◽  
Temperature Dependence ◽  
Ionic Character ◽  
Nucleophilic Displacement ◽  
Wide Range ◽  
Specific Factors ◽  
The Individual ◽  
Hydrolysis Of ◽  
Group 1

The temperature dependence of the rates of hydrolysis of a series of substituted benzyl nitrates in water provided estimates of the heat capacities of activation. These values varied with the substituent over a wide range (−28 → −101 cal mol−1 deg−1).An approximate parallelism has been found to exist between the ΔCp≠ values and kinetic α-deuterium effects obtained for the nitrates and chlorides.While recognizing the existence of specific factors contributing to individual differences, the relative values of these parameters for the individual members of the two series provide a useful measure of the ionic character of the transition state.

Neutral Solvolysis of Acyl Carbon and the Temperature Dependence of the Kinetic Solvent Isotope Effect

1975 ◽  
Vol 53 (6) ◽  
pp. 869-877 ◽  
Author(s):  
B. Rossall ◽  
R. E. Robertson
Keyword(s):  
Temperature Dependence ◽  
Isotope Effect ◽  
Solvent Isotope Effect ◽  
Acyl Carbon ◽  
Rate Of Hydrolysis ◽  
Solvent Isotope ◽  
Neutral Conditions ◽  
Hydrolysis Of

The temperature dependence of the rate of hydrolysis of benzoic, phthalic, and succinic anhydrides have been determined in H2O and D2O under "neutral" conditions. Corresponding data have been obtained for methyl trifluoroacetate. While both series supposedly react by the same BAc2 mechanism, remarkable differences are made obvious by this investigation. Possible sources of such differences are proposed.

Studies in Solvolysis. Part VII. The Neutral Hydrolysis of Methyl Perchlorate

1975 ◽  
Vol 53 (20) ◽  
pp. 3106-3115 ◽  
Author(s):  
Ross Elmore Robertson ◽  
Adrianna Annesa ◽  
John Marshall William Scott
Keyword(s):  
Heat Capacity ◽  
Carbon Atom ◽  
Temperature Dependence ◽  
Thermodynamic Parameters ◽  
Isotope Effect ◽  
Perchlorate Ion ◽  
Rate Of Hydrolysis ◽  
Leaving Groups ◽  
Hydrolysis Of

The temperature dependence of the rate of hydrolysis of methyl perchlorate has been measured and the entropy (ΔS≠), enthalpy (ΔH≠), and heat capacity (ΔCp≠) of activation calculated. The measurements confirm that the perchlorate ion is superior to all other leaving groups in water. The isotope effect related to the hydrolysis of methyl-d3 perchlorate has been measured at three temperatures and shown to be inverse. The thermodynamic parameters and the isotope effect were examined with respect to the mechanism of substitution at a primary carbon atom.

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.

The Hydrolysis of Bis(2-chloroethyl) Sulfide (Sulfur Mustard) in Aqueous Mixtures of Ethanol, Acetone and Dimethyl Sulfoxide

1993 ◽  
Vol 46 (3) ◽  
pp. 293 ◽  
Author(s):  
RI Tilley
Keyword(s):  
Transition State ◽  
Dimethyl Sulfoxide ◽  
Rate Constants ◽  
Charge Separation ◽  
Sulfur Mustard ◽  
Transition States ◽  
Aqueous Mixtures ◽  
Sulfide Sulfur ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

The rate of hydrolysis of bis (2-chloroethyl) sulfide (sulfur mustard) in aqueous mixtures of ethanol, acetone and dimethyl sulfoxide has been measured and compared with previously reported values. Rate constants in water at 25°C for the two consecutive hydrolysis reactions undergone by sulfur mustard were estimated to be (2.93�0.15)×10-3 and (3.87�0.14)×10-3 s-1. Charge separation of 0.42 in the transition states was indicated together with significant solvation of the positive end of the transition state dipoles.

Lanthanum ion catalysis of nucleophilic displacement reactions of monoesters of methyl phosphonic acid

1969 ◽  
Vol 47 (23) ◽  
pp. 4383-4387 ◽  
Author(s):  
R. J. Withey
Keyword(s):  
Aqueous Solution ◽  
Phosphonic Acid ◽  
Methylphosphonic Acid ◽  
Nucleophilic Displacement ◽  
Displacement Reactions ◽  
Lanthanum Ion ◽  
Rate Of Hydrolysis ◽  
Catalytic Effects ◽  
Hydrolysis Of

The catalytic effects of lanthanum ion on the rate of hydrolysis of p-nitrophenyl hydrogen methylphosphonate in aqueous solution at pH > 7.0 are reported. Increases in rate by a factor of about 3.6 × 104 have been observed. No such catalysis was found for diesters of methylphosphonic acid.

Hydrolysis of α-bromoisobutyrate ion in water

1967 ◽  
Vol 45 (18) ◽  
pp. 2071-2077 ◽  
Author(s):  
B. N. Hendy ◽  
W. A. Redmond ◽  
R. E. Robertson
Keyword(s):  
Temperature Dependence ◽  
Isotope Effect ◽  
Deuterium Isotope Effect ◽  
Detailed Mechanism ◽  
Temperature Range ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

The temperature dependence of the rate of hydrolysis of α-bromoisobutyrate ion in water was determined over a temperature range 9–37 °C. From these data corresponding values of ΔH≠, ΔS≠, and ΔCP≠ have been derived. The implication of these terms, together with corresponding data for hydrolysis in D2O and for the secondary deuterium isotope effect from the hydrolysis of (CD3)2CBrCOO−, provide a basis for reexamining the detailed mechanism with particular reference to accompanying solvent reorganization.

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.

HYDROLYSIS OF A SERIES OF PRIMARY ALKYL CHLOROSULFATES: ENTROPY OF ACTIVATION AS A CRITERION OF FRAGMENTATION IN SOLVOLYTIC REACTIONS

1965 ◽  
Vol 43 (3) ◽  
pp. 556-564 ◽  
Author(s):  
E. Buncel ◽  
J. P. Millington
Keyword(s):  
Transition State ◽  
Multiple Bond ◽  
Aqueous Dioxane ◽  
Methyl Ethyl ◽  
Straight Chain ◽  
Leaving Group ◽  
Entropy Of Activation ◽  
Hydrolysis Of ◽  
Chlorine Bond

The solvolysis of the series of alkyl chlorosulfates, ROSO2Cl, where R = methyl, ethyl, n-propyl, isobutyl, and neopentyl, has been studied in 10 M aqueous dioxane. The relative reactivities fit well a solvolytic mechanism involving displacement by water on carbon, with OSO2Cl as the leaving group. The change in mechanism of solvolysis from bimolecular with the straight-chain chlorosulfates to unimolecular with neopentyl chlorosulfate is shown by the absence of the lyate ion effect and the observation of rearrangement in the latter case.The entropies of activation in chlorosulfate solvolysis appear to be abnormally large. It is proposed that the abnormal ΔS≠ indicates a transition state in which both carbon–oxygen and sulfur–chlorine bond weakening occurs. It is shown that some other solvolytic reactions that are characterized by abnormally high entropies of activation may be interpreted on the basis of multiple bond fission (fragmentation). The mechanism of SNi reactions is considered in this context.

REACTIONS OF ARYLSULPHONIC ESTERS: III. ON THE HYDROLYSIS OF METHYL p-METHYLBENZENESULPHONATE

1955 ◽  
Vol 33 (10) ◽  
pp. 1536-1543 ◽  
Author(s):  
R. E. Robertson
Keyword(s):  
Specific Heat ◽  
Temperature Dependence ◽  
Specific Solvation ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Reaction In Water

A study of the temperature dependence for the rate of hydrolysis of methyl p-methylbenzenesulphonate shows the specific heat of activation for this reaction in water to be 33.45 ± 3 cal./mole degree. A comparison with the corresponding term for other methyl compounds reveals differences apparently characteristic of the anionic portion of the molecule. These differences are discussed in terms of specific solvation.

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