Solute molecular volume

In our approach, to estimate the size of the cavity, the solute molecular volume (Vm) is needed. For a spherical cavity the radius is related to the molecular volume (which can be evaluated from the experimental density) according to ... 

Logarithmic bioconcentration factors have been shown to be correlated with the logarithmic octa-nol/water partition coefficient in aquatic organisms (Davies and Dobbs, 1984 de Wolf et al., 1992 Isnard and Lambert, 1988) and fish (Davies and Dobbs, 1984 Kenaga, 1980 Isnard and Lambert, 1988 Neely et al., 1974 Ogata et al., 1984 Oliver and Niimi, 1985). In addition, bioconcentration factors are well correlated by a linear solvation energy relationship (coimnonly known as LSER) that includes the intrinsic solute molecular volume and solvatochromic parameters that measnre hydrogen bond acceptor basicity and donor acidity of the componnd (Park and Cho, 1993). 

Enrique Moles, 1883-1953. Distinguished Spanish chemist and pharmacist. Professor of Inorganic and Physical Chemistry in the Faculty of Chemical Sciences at Madrid. His papers on non-aqueous solutions, molecular volumes and additivity, inorganic complexes, and atomifc weight determinations were published in the leading journals of Spain, England, France, Italy, and the Netherlands. See... 

VbA solute molecular volume at normal boiling point, m3/kmol 0.0256 m3/kmol for oxygen [See Perry and Chilton (p.3 -233,1973) for extensive table]... 

The solubilities of nonpolymeric solutes in supercritical fluids such as CO2 can be predicted if the properties that describe the solute-solute interactions are chosen properly (35). For polyaromatic hydrocarbons, examples of appropriate solute properties include the enthalpy of vaporization and the solute molecular volume. To further understand the role of solute-solvent interactions on solubilities and selectivities, it is instructive to define an enhancement factor E as the actual solubility, y>2, divided by the solubility in an ideal gas, with the result E = y2 This factor is a normalized solubility... 

Those involving solution nonideality. This is the most serious approximation in polymer applications. As we have already seen, the large differences in molecular volume between polymeric solutes and low molecular weight solvents is a source of nonideality even for athermal mixtures. 

It is seen that if the diffusivity is to be correlated with the molecular weight, then a knowledge of the density of the solute is also necessary. The result of the correlation of the reciprocal of the diffusivity of the 69 different compounds to the product of the cube root of the molecular volume and the square root of the molecular weight is shown in Figure 1. A summary of the errors involved is shown in Figures 2 and 3... 

F = Function of the molecular volume of the solute. Correlations for this parameter are given in Figure 7 as a function of the parameter (j), which is an empirical constant that depends on the solvent characteristics. As points of reference for water, (j) = 1.0 for methanol, (j) = 0.82 and for benzene, (j) = 0.70. The two-film theory is convenient for describing gas-liquid mass transfer where the pollutant solute is considered to be continuously diffusing through the gas and liquid films. 

Small particle size resins provide higher resolution, as demonstrated in Fig. 4.41. Low molecular weight polystyrene standards are better separated on a GIOOOHxl column packed with 5 /u,m resin than a GlOOOHg column packed with 10 /Ltm resin when compared in the same analysis time. Therefore, smaller particle size resins generally attain a better required resolution in a shorter time. In this context, SuperH columns are best, and Hhr and Hxl columns are second best. Most analyses have been carried out on these three series of H type columns. However, the performance of columns packed with smaller particle size resins is susceptible to some experimental conditions such as the sample concentration of solution, injection volume, and detector cell volume. They must be kept as low as possible to obtain the maximum resolution. Chain scissions of polymer molecules are also easier to occur in columns packed with smaller particle size resins. The flow rate should be kept low in order to prevent this problem, particularly in the analyses of high molecular weight polymers. 

The value indicated is O.SA larger than the computed molecular volume in order to account for the van der Waals radii of the surrounding solute molecules. 

Continuum models of solvation treat the solute microscopically, and the surrounding solvent macroscopically, according to the above principles. The simplest treatment is the Onsager (1936) model, where aspirin in solution would be modelled according to Figure 15.4. The solute is embedded in a spherical cavity, whose radius can be estimated by calculating the molecular volume. A dipole in the solute molecule induces polarization in the solvent continuum, which in turn interacts with the solute dipole, leading to stabilization. 

V4 is the molecular volume of the solute (m /kmol). Values for simple molecules are given in Table 10.4. For more complex molecules, V. is calculated by summation of the atomic volume and other contributions given in Table 10.4. 

The solvent triangle classification method of Snyder Is the most cosDBon approach to solvent characterization used by chromatographers (510,517). The solvent polarity index, P, and solvent selectivity factors, X), which characterize the relative importemce of orientation and proton donor/acceptor interactions to the total polarity, were based on Rohrscbneider s compilation of experimental gas-liquid distribution constants for a number of test solutes in 75 common, volatile solvents. Snyder chose the solutes nitromethane, ethanol and dloxane as probes for a solvent s capacity for orientation, proton acceptor and proton donor capacity, respectively. The influence of solute molecular size, solute/solvent dispersion interactions, and solute/solvent induction interactions as a result of solvent polarizability were subtracted from the experimental distribution constants first multiplying the experimental distribution constant by the solvent molar volume and thm referencing this quantity to the value calculated for a hypothetical n-alkane with a molar volume identical to the test solute. Each value was then corrected empirically to give a value of zero for the polar distribution constant of the test solutes for saturated hydrocarbon solvents. These residual, values were supposed to arise from inductive and... 

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