Solvation free energy, comparison

C. Curutchet, M. Orozco, F. J. Luque, B. Mennucci and J. Tomasi, Dispersion and repulsion contributions to the solvation free energy comparison of quantum mechanical and classical approaches in the polarisable continuum model, J. Comput. Chem. 27 (2006) 1769-1780. 

Parchment et al25 also found reasonable agreement between the PCM and MD-FEP methods. Simpler SCRF approaches however differ widely. For example spherical cavity ab initio SCRF calculations predict a solvation free energy of the keto-N2H tautomer of 3-hydroxypyrole (see Sec. 3.1) of -93.5 kJ/mol in comparison to the PCM and FEP values of -9.0 kJ/mol and -12.5 kJ/mol respectively. 

This paper provides an example of how accurate continuum models can open the door to the modeling of condensed-phase processes where solvation free energies have a very large influence on reaction energetics. It additionally offers a case study of how to first choose a model on the basis of experimental/tlieoretical comparisons over a relevant data set, and then apply tliat model with a greater expectation for its utility. The generality of this approach to other (equilibrium) electrochemical reactions seems promising. 

The atomic radii may be further refined to improve the agreement between experimental and theoretical solvation free energies. Work on this direction has been done by Luque and Orozco (see [66] and references cited therein) while Barone et al. [67] defined a set of rules to estimate atomic radii. Further discussion on this point can be found in the review by Tomasi and co-workers [15], It must be noted that the parameterization of atomic radii on the basis of a good experiment-theory agreement of solvation energies is problematic because of the difficulty to separate electrostatic and non-electrostatic terms. The comparison of continuum calculations with statistical simulations provides another way to check the validity of cavity definition. A comparison between continuum and classical Monte Carlo simulations was reported by Costa-Cabral et al. [68] in the early 1980s and more recently, molecular dynamics simulations using combined quantum mechanics and molecular mechanics (QM/MM) force-fields have been carried out to analyze the case of water molecule in liquid water [69],... 

Figure 17-6. Comparison of the solvation free energy A//, for typical solute molecules in solvent water. The thermodynamic state is specified by the solvent density and temperature...

Ewing, P. J. and T. P. Lybrand. (1993). A comparison of perturbation method and PB electrostatic calculations for estimation of relative solvation free energies. J. Phys. Chem. 98 1748-52. 

Single electron transfer (SET), as antioxidant mechanism 844, 896, 897 Size exclusion chromatography 953 Slash pine bark, phenolic compounds in 944 Smiles rearrangement 466-470, 759 S Ar reactions 673 Soil samples, phenolic compounds in, analysis of 932, 965, 972, 985 field screening of 938 Sol-gel technique 1082 Solid acid catalysis 612-621 Solid-phase extraction (SPE) 930-933, 936, 942, 944-950, 955, 958, 960, 962-964, 969, 972, 985, 986, 995, 1354 Solvation energy 500, 992 Solvation free energy 5 Solvatochromic comparison method, for solvent hydrogen-bond basicity 591 Solvent effects,... 

The calculated individual contributions to the total aqueous solvation free energies of 30 organic compounds are given in Table 1. The electrostatic (SCRF) contributions were calculated using semiempirical AMI (Austin Model 1 [60,61]) method. The dispersion energies were calculated using INDO/1 parameterization [62] and AMI optimized molecular geometries in solution. A comparison of different columns in Table 1 with the experimental solvation... 

Lee, M. S., and Olson, M. A. (2013). Comparison of volume and surface area nonpolar solvation free energy terms for implicit solvent simulations,/. Chem. Phys. 139, pp. 044119 1-6. 

Validation of the OPLS2.0 force field includes comparison to quantum mechanical energy profiles and experimental solvation free energies. For the latter, we performed explicit solvent molecular dynamics free energy perturbation simulations on a set of 239 diverse small molecules [80]. Compared with other popular force fields... 

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