Solvent cavity

Two important contributions to the study of solvation effects were made by Bom (in 192( and Onsager (in 1936). Bom derived the electrostatic component of the free energ) c solvation for placing a charge within a spherical solvent cavity [Bom 1920], and Onsagi extended this to a dipole in a spherical cavity (Figure 11.21) [Onsager 1936]. In the Bor... 

The self-consistent reaction held (SCRF) method is an adaptation of the Poisson method for ah initio calculations. There are quite a number of variations on this method. One point of difference is the shape of the solvent cavity. Various models use spherical cavities, spheres for each atom, or an isosurface... 

There have been some attempts to compute nonlinear optical properties in solution. These studies have shown that very small variations in the solvent cavity can give very large deviations in the computed hyperpolarizability. The valence bond charge transfer (VB-CT) method created by Goddard and coworkers has had some success in reproducing solvent effect trends and polymer results (the VB-CT-S and VB-CTE forms, respectively). 

Figures 17A and 17B (p. 183) show energy as a function of rotation for a series of 1-substituted acetaldehydes, with 6 = 0° in the syn conformation and 6 = 180° in the anti conformation. The calculations were done using the PM3 method. Figure 17A for a vacuum, whereas Fig. 17B is for a solvent cavity with a dielectric constant of 4." The table gives the calculated barriers. Discuss the following aspects (a) rationalize the order Br > Cl > F for syn conformers (b) rationalize the shift to favor the am. conformation in the more polar environment. 

The mixed solvent models, where the first solvation sphere is accounted for by including a number of solvent molecules, implicitly include the solute-solvent cavity/ dispersion terms, although the corresponding tenns between the solvent molecules and the continuum are usually neglected. Once discrete solvent molecules are included, however, the problem of configuration sampling arises. Nevertheless, in many cases the first solvation shell is by far the most important, and mixed models may yield substantially better results than pure continuum models, at the price of an increase in computational cost. 

Where FCl is the solute gas-liquid partition coefficient, r is the tendency of the solvent to interact through k- and n-electron pairs (Lewis basicity), s the contribution from dipole-dipole and dipole-induced dipole interactions (in molecular solvents), a is the hydrogen bond basicity of the solvent, b is its hydrogen bond acidity and I is how well the solvent will separate members of a homologous series, with contributions from solvent cavity formation and dispersion interactions. 

Hermann, R. B. (1971) Theory of hydrophobic bonding. II. The correlation of hydrocarbon solubility in water with solvent cavity surface area. J. Phys. Chem. 76, 2754—2758. 

Non-electrostatic terms, comprising the solvent-solvent cavity term and solute-solvent van der Waals term, may be linearly related to solvent-accessible surface area (SA)... 

When an electron is injected into a polar solvent such as water or alcohols, the electron is solvated and forms so-called the solvated electron. This solvated electron is considered the most basic anionic species in solutions and it has been extensively studied by variety of experimental and theoretical methods. Especially, the solvated electron in water (the hydrated electron) has been attracting much interest in wide fields because of its fundamental importance. It is well-known that the solvated electron in water exhibits a very broad absorption band peaked around 720 nm. This broad absorption is mainly attributed to the s- p transition of the electron in a solvent cavity. Recently, we measured picosecond time-resolved Raman scattering from water under the resonance condition with the s- p transition of the solvated electron, and found that strong transient Raman bands appeared in accordance with the generation of the solvated electron [1]. It was concluded that the observed transient Raman scattering was due to the water molecules that directly interact with the electron in the first solvation shell. Similar results were also obtained by a nanosecond Raman study [2]. This finding implies that we are now able to study the solvated electron by using vibrational spectroscopy. In this paper, we describe new information about the ultrafast dynamics of the solvated electron in water, which are obtained by time-resolved resonance Raman spectroscopy. 

The solvation free energy is usually considered to consist of a solvent-solvent cavity term (Gcav), a solute-solvent van der Waals term (Gvsolute-solvent electrostatic polarization term (Ges) (Eq. 2.37). 

In a recent approach that was successfully tested for small hydrocarbons the solvation was treated semianalytically as a statistical continuum1831. The method treats the sum of the solvent-solvent cavity (Gcav) and the solute-solvent van der Waals (Gvdw) terms by determining the solvent-accessible surface1841, and the solute-solvent electrostatic polarization term (Ges) is calculated by a modified version of the generalized Bom equation183,851. 

All attempts (74,89) to find a sensible, quantitative relation between the wavelength of maximum absorption ( max) and typical macroscopic properties of the solvent (i.e., dielectric constant) have so far failed (146). However, the size of the solvent cavity in which the electron is trapped also plays a decisive role (101) in determining the transition energy [Eqs. (2), (3)], and the solvent dependence of A.max might well indicate a variation in cavity size from solvent to solvent. In this spirit, Dorfman and Jou (48) have evaluated cavity radii on the basis of the simple Jortner model for the solvated electron. The values are shown in Fig. 3, which shows a plot of the optical transition energy max versus... 

M. A. Aguilar and F. J. Olivares del Valle, Solute-solvent interactions, a simple procedure for constructing the solvent cavity for retaining a molecular solute, Chem. Phys., 129 (1989) 439-450. 

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