ENTROPY-ENTHALPY COMPENSATION BEHAVIOR REVISITED

2004 ◽  
Vol 03 (04) ◽  
pp. 511-520 ◽  
Author(s):  
WILLIAM R. KIRK
Keyword(s):  
Free Energy ◽  
Statistical Mechanics ◽  
Solvent Effect ◽  
Liquid State ◽  
Compensation Behavior ◽  
Solute Interaction ◽  
Entropically Driven ◽  
Thermodynamic Perturbation

The origin of genuine (not statistically spurious) entropy-enthalpy compensation is investigated within standard liquid state statistical mechanics formalism. We treat two extreme cases of solvent-solute interaction: (1) those in which the changes "internal" to the solute dominate, and (2) those in which the solvent effect is dominant. They are evaluated in different ways, and lead to different predictions for compensation behavior. The first involves a conventional "thermodynamic perturbation" formalism.1,2 The second case leads to an Ornstein–Zernicke-like relationship that predicts predominantly entropically driven changes in free energy of reaction.

scholarly journals Studies on the effect of Aquo-Dioxan Solvent System on the biochemical behaviour of the Substituted Valerates

2020 ◽  
Vol 16 (5) ◽  
pp. 63-71
Author(s):  
SUSHMA KUMARI ◽  
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Hydrolysis Product ◽  
Solvent System ◽  
Simultaneous Increase ◽  
Solute Interaction ◽  
Reaction Media ◽  
Energy Activation

Valerates and Substituted Valerates have been found to be useful for humanbeings as its hydrolysis product i.e. valence acid is used in the society in the form of perfumes flavours platister, vinyl stabilizer and pharmaceuyicals. With a views to study the solvent effect of 1:4 dioxan on the biochemical behivour of the hydrolysis product of a substituted valerate, the kinetic of Alkali catalysed of mothyl iso-valerate was studies in aquodioxan media. Increase observed in free energy activation with simultaneous increase in the value of both the activation H* and S*, it is concluded that in the presence of dioxan with reaction media, the reaction becomes enthaipy dominating and entropy controlled. From the evaluated values of the reaction which comes to be 329.0, it is inferred that Barclay-Butler rule is obeyed by the reaction and there is strong solvent- solute interaction in presence of dioxan the reaction media.

Kinetics of Ion-Pair Effect of Aquation of Bromopentaammine Cobalt(III) Complex in Different Dicarboxylate Media

2011 ◽  
Vol 324 ◽  
pp. 166-169 ◽  
Author(s):  
Farah Zeitouni ◽  
Gehan El-Subruiti ◽  
Ghassan Younes ◽  
Mohammad Amira
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Compensation Effect ◽  
Ion Pairing ◽  
Reaction Rates ◽  
Ion Pair ◽  
Free Energy Of Activation ◽  
Different Types ◽  
Different Temperatures ◽  
Kinetics Of

The rate of aquation of bromopentaammine cobalt(III) ion in the presence of different types of dicarboxylate solutions containing tert-butanol (40% V/V) have been measured spectrophotometrically at different temperatures (30-600°C) in the light of the effects of ion-pairing on reaction rates and mechanism. The thermodynamic and extrathermodynamic parameters of activation have been calculated and discussed in terms of solvent effect on the ion-pair aquation reaction. The free energy of activation ∆Gip* is more or less linearly varied among the studied dicarboxylate ion-pairing ligands indicating the presence of compensation effect between ∆Hip* and ∆Sip*. Comparing the kip values with respect of different buffers at 40% of ter-butanol is introduced.

Free-Energy Calculations

2006 ◽  
Author(s):  
Vasily Bulatov ◽  
Wei Cai
Keyword(s):  
Free Energy ◽  
Melting Temperature ◽  
Open System ◽  
Finite Temperature ◽  
Liquid State ◽  
Crystalline State ◽  
Minimum Energy ◽  
Temperature Limit ◽  
Free Energy Calculations ◽  
Energy Calculations

Free energy is of central importance for understanding the properties of physical systems at finite temperatures. While in the zero temperature limit the system should evolve to a state of minimum energy (Section 2.3), this is not necessarily the case at a finite temperature. When an open system exchanges energy with the outside world (a thermostat) and maintains a constant temperature, its evolution proceeds towards minimizing its free energy. For example, a crystal turns into a liquid when the temperature exceeds its melting temperature precisely because the free energy of the liquid state becomes lower than that of the crystalline state. In the context of dislocation simulations, free energy is all important when one has to decide which of the possible core configurations the dislocation is likely to adopt at a given temperature.

Thermodynamic studies in solution. Part IV. Solvent effect on the solvolysis of tert-butyl chloride. A new treatment of the experimental data

1979 ◽  
Vol 57 (5) ◽  
pp. 500-502 ◽  
Author(s):  
Joaquim Jose Moura Ramos ◽  
Jacques Reisse ◽  
M. H. Abraham
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Free Energies ◽  
Butyl Chloride ◽  
Activation Free Energy ◽  
Tert Butyl ◽  
New Treatment ◽  
The One ◽  
Activated Complex ◽  
Tert Butyl Chloride

A new treatment of the solvent effect on the solvolysis of tert-butyl chloride is proposed. This treatment is based on activation free energy measurements and on transfer free energy measurements of the reactant (R) on the one hand and of a model (M) of the activated complex (AC) on the other hand. Solute–solvent interaction free energies for the reactant, the activated complex and the model compound are estimated. This estimation involves the calculation of the free energy of cavity formation of these various solutes (R, AC, and M) in all the solvents. These cavity terms, which are a function of the cohesive properties of the solvent and of the surface of the cavity do not reflect the electronic structure of the solute whereas the interaction free energy term does. The method we propose can be described as a new 'experimental' approach for the study of the charge separation in an activated complex.

A reaction density functional theory study of the solvent effect in prototype SN2 reactions in aqueous solution

2019 ◽  
Vol 21 (45) ◽  
pp. 24876-24883 ◽  
Author(s):  
Cheng Cai ◽  
Weiqiang Tang ◽  
Chongzhi Qiao ◽  
Peng Jiang ◽  
Changjie Lu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Density Functional Theory ◽  
Free Energy ◽  
Solvent Effect ◽  
Density Functional ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Sn2 Reactions ◽  
Energy Profiles ◽  
Free Energy Profiles

Reaction density functional theory (RxDFT), combining quantum DFT with classical DFT, has been employed to investigate the solvent effect and free energy profiles of SN2 reactions in aqueous solution.

On the theory of the liquid state

1941 ◽  
Vol 37 (3) ◽  
pp. 252-275 ◽  
Author(s):  
R. Fürth
Keyword(s):  
Thermodynamic Properties ◽  
Statistical Mechanics ◽  
Liquid State ◽  
Classical Statistical Mechanics

The theory of holes in liquids, suggested in a previous paper, is developed by means of classical statistical mechanics, and it is shown that the principal thermodynamic properties of the liquid state can be derived in this way and that they are in numerical agreement with the experiments.

Studies on the iodide–triiodide equilibrium

1977 ◽  
Vol 55 (5) ◽  
pp. 792-797 ◽  
Author(s):  
Robert L. Benoit ◽  
Michael F. Wilson ◽  
Sing-Yeung Lam
Keyword(s):  
Free Energy ◽  
Solvent Effect ◽  
Gas Phase ◽  
Formation Enthalpy ◽  
Aprotic Solvents ◽  
Free Energies ◽  
Potentiometric Measurements ◽  
Cast Doubt ◽  
Transfer Parameters ◽  
The Enthalpy Of Formation

The solvent effect on the iodide–triiodide equilibrium has been investigated by means of calorimetric and potentiometric measurements. The aprotic solvents studied were nitromethane, nitrobenzene, sulfolane, acetonitrile, propylene carbonate, acetophenone, dimethylformamide, dimethylsulfoxide, and o-dichlorobenzene. The resulting enthalpy and free energy changes imply that the variations of the enthalpies and free energies of transfer of the iodide and triiodide ions probably are small and that there is an important non-coulombic contribution to these transfer parameters. Values were obtained for the enthalpy of formation of two solid triiodides, which together with values for other triiodides, cast doubt on reported calculated lattice enthalpies of triiodides and formation enthalpy of I3− ion in the gas phase. This latter formation enthalpy is found to be, from our solution data, more negative than −22 kcal mol−1.

Sign in / Sign up

Export Citation Format

Share Document