Heat Capacity of Activation for the Hydrolysis of Cyclopropylcarbinyl and Cyclobutyl Chlorides in Water1a

1966 ◽  
Vol 88 (12) ◽  
pp. 2666-2668 ◽  
Author(s):  
Ching Yong Wu ◽  
R. E. Robertson
Keyword(s):  
Heat Capacity ◽  
Hydrolysis Of

Heat capacity of activation for the hydrolysis of methanesulfonyl chloride and benzenesulfonyl chloride in light and heavy water

1969 ◽  
Vol 47 (22) ◽  
pp. 4199-4206 ◽  
Author(s):  
R. E. Robertson ◽  
B. Rossall ◽  
S. E. Sugamori ◽  
L. Treindl
Keyword(s):  
Heat Capacity ◽  
Free Energy ◽  
Temperature Dependence ◽  
Heavy Water ◽  
Bond Formation ◽  
Sulfonyl Chlorides ◽  
Benzenesulfonyl Chloride ◽  
Methanesulfonyl Chloride ◽  
Hydrolysis Of ◽  
Parameter Temperature Dependence

Rates of solvolysis of methanesulfonyl chloride and benzenesulfonyl chloride have been determined in H2O and D2O. The free energy, enthalpy, entropy, and heat capacity of activation were calculated. The exceptional accuracy of the data permitted an estimation of dΔCp≠/dT from a four parameter temperature dependence of the kinetic rates.From these data we conclude that both sulfonyl chlorides hydrolyse by the same mechanism (Sn2) The change in R from CH3 to C6H5 in RSO2Cl did not alter ΔCp≠ but ΔS≠ (20°) was changed from −8.32 to −13.25 cal deg−1 mole−1, respectively. The significance of this difference is attributed to the probability of bond formation rather than to differences in solvent reorganization.

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.

Heat Capacity of Activation for the Hydrolysis of 2,2-Dihalopropanes1

1966 ◽  
Vol 88 (7) ◽  
pp. 1363-1365 ◽  
Author(s):  
A. Queen ◽  
R. E. Robertson
Keyword(s):  
Heat Capacity ◽  
Hydrolysis Of

The Hydrolysis of Disubstituted Alkyl Phosphorochloridates and N,N,N′,N′-Tetra-stibstituted Phosphorodiamidic Chlorides in Water and Deuterium Oxide: Heat Capacity of Activation and Kinetic Solvent Isotope Effects

1973 ◽  
Vol 51 (4) ◽  
pp. 597-603 ◽  
Author(s):  
E. C. F. Ko ◽  
R. E. Robertson
Keyword(s):  
Heat Capacity ◽  
Thermodynamic Parameters ◽  
Alkyl Group ◽  
Deuterium Oxide ◽  
Isotope Effects ◽  
Potential Relationship ◽  
Mechanism Of Reaction ◽  
Solvent Isotope ◽  
Hydrolysis Of ◽  
Solvent Isotope Effects

The pseudo-thermodynamic parameters, ΔH≠, ΔS≠, and ΔCp≠ and the kinetic solvent isotope effects have been determined for the three alkyl-phosphorochloridates, where the alkyl group is ethylisopropyl and n-propyl; for tetra-methyl and tetra-ethyl phosphorodiamidic chlorides; the di-n-propyl and di-isopropyl analog, the di(isopropylmethylcarbinyl)phosphorochloridate and the tetra-ethylthiophosphorodiamidic chloride. These compounds have a potential relationship to compounds used as insecticides and as polymers. The mechanism of reaction is discussed on the basis of these data.

An Examination of the Heat Capacity of Activation for the Hydrolysis of t-Butyl Chloride in Water

1972 ◽  
Vol 50 (2) ◽  
pp. 167-175 ◽  
Author(s):  
J. M. W. Scott ◽  
R. E. Robertson
Keyword(s):  
Heat Capacity ◽  
Alternative Hypothesis ◽  
Ion Pairs ◽  
Heat Capacities ◽  
Butyl Chloride ◽  
Methyl Halides ◽  
Displacement Reactions ◽  
Arrhenius Temperature Dependence ◽  
Hydrolysis Of ◽  
Arrhenius Temperature

The influence of ion-pair intermediates on solvolytic displacement reactions is considered for cases where the observed rate constant is complex.Such complex and composite rate constants under certain conditions may show deviations from the Arrhenius temperature dependence law. The deviations will manifest themselves as "spurious" positive and/or negative heat capacities of activation, superimposed on the real heat capacity terms.The hypothesis of Albery and Robinson (1) which proposes that the heat capacity of activation for t-butyl chloride is entirely "spurious" in the sense outlined above, is critically evaluated and rejected. An alternative hypothesis that considers the heat capacity to be a manifestation of solvation effects is retained.The mechanism of the hydrolysis of both the methyl and t-butyl halides in water is discussed and the kinetic laws appropriate to each are shown to be consistent with real heat capacities of activation. The mechanism proposed differs from the classical SN1–SN2 description. Both series of substrates are considered to give rise to intimate-ion-pairs but in the case of the methyl halides these react further by a path which involves the nucleophilicity of the solvent in a kinetically significant way. In the cases of the tertiary compounds, solvent separation of ion-pairs becomes kinetically significant. The nucleophilic component which characterizes the destruction of the solvent-separated ion-pairs for the tertiary compounds is kinetically insignificant.

The Hydrolysis of t-Butyl Chloride in Aquo-Organic Mixtures: Heat Capacity of Activation and Solvent Structure

1972 ◽  
Vol 50 (9) ◽  
pp. 1353-1360 ◽  
Author(s):  
R. E. Robertson ◽  
S. E. Sugamori
Keyword(s):  
Heat Capacity ◽  
Temperature Dependence ◽  
High Water ◽  
Remarkable Difference ◽  
Solvent Structure ◽  
Butyl Chloride ◽  
Organic Mixtures ◽  
A Value ◽  
Polar Solutes ◽  
Hydrolysis Of

The temperature dependence of the rate of solvolysis of t-butyl chloride in mixtures of tetrahydrofuran and of acetonitrile in water have been determined. In the high-water range both minor co-solvents lead to a reduction in the value of ΔH≠ similar to that found previously where alcohol was the co-solvent. However, a remarkable difference in the values of [Formula: see text] across the same concentration range reflected a difference in the effect of these two co-solvents on the structural properties of the several solvent media. Where tetrahydrofuran or alcohols are the minor co-solvent, [Formula: see text] becomes much more negative until that concentration is reached where the quasi-aqueous structure collapses. Where acetonitrile is the minor co-solvent [Formula: see text] becomes more positive relative to the value found for hydrolysis in water until a value of about −40 cal deg−1 mol−1 is reached. The implication of these findings concerning the nature of solvation of weakly polar solutes in such mixtures is discussed.

Studies in Solvolysis. Part VI. An Examination of the Heat Capacity of Activation for the Hydrolysis of 4-Methoxybenzyl Trifluoroacetate

1975 ◽  
Vol 53 (7) ◽  
pp. 1051-1055 ◽  
Author(s):  
June Gertrude Winter ◽  
John Patrick Barron ◽  
John Marshall William Scott
Keyword(s):  
Heat Capacity ◽  
The Other ◽  
Relative Importance ◽  
Reaction Paths ◽  
Enthalpy Of Activation ◽  
Hydrolysis Of

The heat capacity of activation for the hydrolysis of 4-methoxybenzyl trifluoroacetate in water containing 9.05 × 10−2 mol fraction of acetone has been measured and shown to be positive. This unusual result is consistent with the notion that the ester reacts by two distinct routes: one involving acyl–oxygen fission, the other, alkyl–oxygen fission. The relative importance of the two paths for the 4-methoxy ester has been established quantitatively via a Hammett σ–ρ correlation for a series of 4-substituted-benzyl trifluoroacetates. Such an assessment allows the observed heat capacity, entropy, and enthalpy of activation to be factored into parts appropriate to each of the two reaction paths.

Solvation differences in the hydrolysis of certain alicyclic bromides

1970 ◽  
Vol 48 (8) ◽  
pp. 1296-1301 ◽  
Author(s):  
H. S. Golinkin ◽  
D. M. Parbhoo ◽  
R. E. Robertson
Keyword(s):  
Heat Capacity ◽  
Isotope Effects ◽  
Trans Isomers ◽  
Apparent Heat Capacity ◽  
Deuterium Isotope Effects ◽  
Cis And Trans ◽  
Hydrolysis Of

A detailed study of the hydrolysis in water of the cis and trans cyclopentyl and cyclohexyl bromohydrins reveals significant differences in the apparent heat capacity of activation (ΔCp≠). The cis isomers have values of[Formula: see text]; the same value as found for cyclopentyl bromide, but more negative by 10 caldeg−1 mole−1 than that found for the hydrolysis of cyclohexyl bromide. By contrast, the corresponding value for trans isomers was about −45 cal deg−1 mole−1. The differences in ΔCP≠ can be explained in terms of different mechanisms. Secondary β-deuterium isotope effects of 2.28 for the cis-2-bromocyclopentanol-1-d and 2.45 for cis-2-bromocyclohexanol-1-d confirm hydrogen participation in these cases. The corresponding ketones were the only products detected.

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