Solvation Model for Chloroform Based on Class IV Atomic Charges

Giesen, David J.; Chambers, Clarke A.; Cramer, Christopher J.; Truhlar, Donald G.

doi:10.1021/jp963080v

Cited by 57 publications

(84 citation statements)

References 21 publications

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“…The functional forms for the SM5.4 model have been presented in full detail in the elsewhere (12,14,15). In this section we review those features of the models that are important to understanding the rest of this chapter.…”

Section: Solvation Model 54mentioning

confidence: 99%

Modeling Free Energies of Solvation and Transfer

Giesen

Chambers

Hawkins

et al. 1998

ACS Symposium Series

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The free energy of transfer of a solute from one medium to another, which is the free energy of solvation if the first medium is the gas phase and the second is a liquid-phase solution, controls all solvation and partitioning phenomena. The SM5.4 quantum mechanical solvation model allows for the calculation of (i) partitioning free energies between the gas phase and a solvent (i.e., free energies of solvation) or (ii) partitioning free energies between two solvents. The model provides a framework for interpreting the factors responsible for differential solvation effects and can be used to predict solvation effects on chemical equilibria and kinetics-examples in this chapter include partitioning of the nucleic acid bases between water and chloroform, solvation effects on anomeric conformational equilibria, and solvation effects on the rate of the Claisen rearrangement.A collection of solute molecules will partition between two (or more) phases so as to equalize the concentration-dependent chemical potential of the solute in all phases (1). This behavior has far reaching consequences in chemistry. For instance, a molecule might have very high specific activity against a target enzyme, but if its concentration in aqueous biophases or fatty tissues is extremely low it may be inefficacious as an oral drug (since it must be carried by the bloodstream and, if the enzyme is locatedintracellularly, it must pass through a lipid bilayer membrane). A second example of medium effects on equilibria is that the fraction of molecules in any one of several potentially accessible conformations can depend significantly on solvent, and this structural equilibrium may have significant effects on molecular properties, recognition, and reactivity. As a final example, medium effects on reaction rates can be viewed as changes in the relative equilibrium concentrations of reactants and activated complexes on going from one environment to the next. These examples 'Corresponding authors

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Section: Solvation Model 54mentioning

confidence: 99%

Modeling Free Energies of Solvation and Transfer

Giesen

Chambers

Hawkins

et al. 1998

ACS Symposium Series

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“…Quantum mechanical treatments for solvation in chloroform have also been developed with continuum models of the solvent in self-consistent reaction field calculations. 22,23 COMPUTATIONAL DETAILS…”

Section: Introductionmentioning

confidence: 99%

Free energies of solvation in chloroform and water from a linear response approach

McDonald

Carlson

Jorgensen

1997

J. Phys. Org. Chem.

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Monte Carlo statistical mechanics simulations were used to compute absolute free energies of solvation in chloroform for 16 organic molecules. The intermolecular interactions were described by classical potential functions consisting of Coulomb and Lennard-Jones interactions. The partial charges for the solutes were derived from fitting to the electrostatic potential surfaces of ab initio 6-31G* wavefunctions. First, free energy perturbation (FEP) calculations yielded relative free energies of solvation. These were converted to absolute quantities through perturbations to the reference molecule, methane, which was annihilated. The average error in the FEP-computed free energies of solvation is 0·8 kcal mol . Combination of the predictions of free energies of solvation in water and chloroform yields partition coefficients, log P, with an average error of 0·3-0·4 log unit.

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“…Eight of the methods considered solvent. In the semiempirical calculations, COSMO [74] and SM5.4 [75] were used. At the HF and DFT levels, SM5.42, [76] C-PCM-UAHF, [77] PCM-UAHF, [78] and Onsager [79] models were used.…”

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confidence: 99%

Experimental and Theoretical Multiple Kinetic Isotope Effects for an S_N2 Reaction. An Attempt to Determine Transition‐State Structure and the Ability of Theoretical Methods to Predict Experimental Kinetic Isotope Effects

Fang

Gao

Ryberg

et al. 2003

Chemistry A European J

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The secondary alpha-deuterium, the secondary beta-deuterium, the chlorine leaving-group, the nucleophile secondary nitrogen, the nucleophile (12)C/(13)C carbon, and the (11)C/(14)C alpha-carbon kinetic isotope effects (KIEs) and activation parameters have been measured for the S(N)2 reaction between tetrabutylammonium cyanide and ethyl chloride in DMSO at 30 degrees C. Then, thirty-nine readily available different theoretical methods, both including and excluding solvent, were used to calculate the structure of the transition state, the activation energy, and the kinetic isotope effects for the reaction. A comparison of the experimental and theoretical results by using semiempirical, ab initio, and density functional theory methods has shown that the density functional methods are most successful in calculating the experimental isotope effects. With two exceptions, including solvent in the calculation does not improve the fit with the experimental KIEs. Finally, none of the transition states and force constants obtained from the theoretical methods was able to predict all six of the KIEs found by experiment. Moreover, none of the calculated transition structures, which are all early and loose, agree with the late (product-like) transition-state structure suggested by interpreting the experimental KIEs.

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Solvation Model for Chloroform Based on Class IV Atomic Charges

Cited by 57 publications

References 21 publications

Modeling Free Energies of Solvation and Transfer

Modeling Free Energies of Solvation and Transfer

Free energies of solvation in chloroform and water from a linear response approach

Experimental and Theoretical Multiple Kinetic Isotope Effects for an S_N2 Reaction. An Attempt to Determine Transition‐State Structure and the Ability of Theoretical Methods to Predict Experimental Kinetic Isotope Effects

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Solvation Model for Chloroform Based on Class IV Atomic Charges

Cited by 57 publications

References 21 publications

Modeling Free Energies of Solvation and Transfer

Modeling Free Energies of Solvation and Transfer

Free energies of solvation in chloroform and water from a linear response approach

Experimental and Theoretical Multiple Kinetic Isotope Effects for an SN2 Reaction. An Attempt to Determine Transition‐State Structure and the Ability of Theoretical Methods to Predict Experimental Kinetic Isotope Effects

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Experimental and Theoretical Multiple Kinetic Isotope Effects for an S_N2 Reaction. An Attempt to Determine Transition‐State Structure and the Ability of Theoretical Methods to Predict Experimental Kinetic Isotope Effects