Solvent effects parameterization

Co2(CO)q system, reveals that the reactions proceed through mononuclear transition states and intermediates, many of which have established precedents. The major pathway requires neither radical intermediates nor free formaldehyde. The observed rate laws, product distributions, kinetic isotope effects, solvent effects, and thermochemical parameters are accounted for by the proposed mechanistic scheme. Significant support of the proposed scheme at every crucial step is provided by a new type of semi-empirical molecular-orbital calculation which is parameterized via known bond-dissociation energies. The results may serve as a starting point for more detailed calculations. Generalization to other transition-metal catalyzed systems is not yet possible. 

O. Takahashi, H. Sawahata, Y. Ogawa and O. Kikuchi, Incorporation of solvent effects into ab initio molecular orbital calculations by the generalized Born formula. Formulation, parameterization, and applications, J. Mol. Struct. (THEOCHEM), 393 (1997) 141-150. 

A great number of reactions have been studied in ILs, and many have been interpreted as evidence of particular properties of the solvent. An overview of the insights gained from such reactions would be a review in itself, and indeed, the interested reader should consult any of a number of reviews on the subject [3, 14, 218]. We note the above reactions because their analysis is specifically geared toward detailed parameterization of polarity, and do not consider cases where the analysis of solvent effects is less detailed. 

The procedure for parameterization of solvent electrophilicity has been criticized, mainly because it was found that the use of t(30) instead of E in the multiple regression treatment of solvent effects is often quite successful see reference [15, 116] for examples. It has been shown that values of t(30) and E are linearly correlated, at least for solvents with an t(30) value of greater than ca. 40 kcal/mol [178]. This calls into question the value of Koppel and Palm s division of t(30) into pure electrophilicity effects and non-specific effects by means of Eq. (7-51). 

Dielectric continuum models such as the Generalized Born Solvent Accessible Surface Area (GB/SA) model are, in conjunction with force fields, excellent tools for fast and reliable calculations of hydration energies and solvent effects on, e.g., conformational equilibria and ligand-receptor interactions. The performance for neutral solutes is very good, whereas calculations on ionic compounds are currently more problematic. A solution to these problems most probably requires force fields that include polarization effects. For optimal accuracy of calculations using a dielectric continuum model, it is a clear advantage if the model is parameterized for the particular force field used. 

The continuum methods are advantageous because solvent effects are treated in a physically reasonable way, the methods require modest computational resources, and their simplicity allows one to easily extend standard methods for treating gas phase systems to the solvent realm. One disadvantage is that continuum model free energy predictions are sensitive to the atomic radii used to define the solute-solvent dielectric interface. However, these radii can effectively be determined by parameterization using small systems [24]. 

Molecular mechanics methods have been used particularly for simulating surface-liquid interactions. Molecular mechanics calculations are called effective potential function calculations in the solid-state literature. Monte Carlo methods are useful for determining what orientation the solvent will take near a surface. Molecular dynamics can be used to model surface reactions and adsorption if the force held is parameterized correctly. 

An series of alternative, generally parameterized methods for introducing the effects of solvent into semi-empirical calculations are termed SMr, where the value of x represents the type and quality of parameterization27-76 81. These methods have potential value in studying solvation effects on the structure, electronic spectra, and reactivity of biologically... 

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