Correlations with dielectric constant

Fields et al. 33) examined the closely related bis (trifluoromethyl) phosphine (Table 14) and found a similar increase in Vp.H with increasing polarity of the solvent. They noted a correlation between /P H and the proton chemical shift (confidence limit of the correlation coefficient was 99.9 %). Again hydrogen bonding was suggested as the principle causative factor since correlations with dielectric constant or refractive index were not found. The two-bond 2/P F was noted to decrease while the three-bond 3/H F coupling constant was solvent invariant (vide infra). 

The nature of the solvent has a high effect on selectivity. For the tested solvents, we observed that the methylcyclohexylketone yield is correlated with dielectric constant. The ring adsorption is inhidited oy polar solvent. 

We view n as an indicator of the internal charge separation, or local polarity, that is present even in molecules with zero dipole moments. It has been shown to correlate with dielectric constants [68] and with an experimentally-based measure of polarity [65]. The total variance, Ot0t> which is the sum of the positive and negative variances, reflects the spread, or range of values, of the surface electrostatic potential. It is particularly sensitive to the positive and negative extremes, because of the terms being squared. We have found Otot to be effective as a measure of a molecule s tendency for noncovalent interactions for example, it enters into our expressions for boiling point [69], enthalpy of vaporization [64], solubilities [70,71], etc. 

The rate law for dimerisation of RuX2(CO)4, in a range of solvents including nitromethane, 1,2-dichloroethane, chloroform, nitrobenzene, dioxan, and methyl isobutyl ketone, is first-order. The suggested ratedetermining step is formation of the five-co-ordinate species RuX2(CO)3. Rates are affected little by the nature of the solvent, and do not correlate with dielectric constant or co-ordinating ability. ... 

No correlation of tribolelectrification with other properties, such as surface or volume resistivity, has been found, although a low correlation with dielectric constant has been reported. ASTM D 3509 is the method for the quantitative measurement of the integrated charge on a surface. Other methods have been developed including some which use probes that traverse the surface to measure a nonuniform distribution of charge (75). 

The actual value of the double-layer capacitance depends on many variables including electrode type, electrochemical potential, oxide layers, electrode surface heterogeneity, impurity adsorption, media type, temperature, etc. [1, pp. 45-48]. Capacitance of the double layer also largely depends on the intermolecular structure of the analyzed media, such as the dielectric constant (or high-frequency permittivity), concentration and types of conducting species, electron-pair donicity, dipole moment, molecular size, and shape of solvent molecules. Systematic correlation with dielectric constant is lacking and complex, due to ionic interactions in the solution. In ionic aqueous solutions with supporting electrolyte ("supported system") the values of -10-60 pF/ cm are typically experimentally observed for thin double layers and solution permittivity e - 80. The double-layer capacitance values for nonpolar dielec-... 

Fedors-type cohesive energy /i ch correlated best with dielectric constant. 

The electronic spectra of HgX2 (X = Cl, Br, I) have been measured in several solvents in an endeavour to characterize the solution structures of these compounds.144 The peak maxima correlate linearly with dielectric constants and Kosower s Z value for solvent polarity in... 

It would seem from our correlations for the alcohols that the continuum model results in a valid expression for the energy states of the electron since the approximations arrived at by Platzman and Franck (23) and by Davydov (8) give the rough magnitude of the binding energy correctly, and the latter shows a trend with dielectric constant in accord with experiment. However, the theory is still in a rather primitive state, and other physical properties of the liquid, in addition to its dielectric behavior, may have to be taken into account. 

In the liquid phase, calculations of the pair correlation functions, dielectric constant, and diffusion constant have generated the most attention. There exist nonpolarizable and polarizable models that can reproduce each quantity individually it is considerably more difficult to reproduce all quantities (together with the pressure and energy) simultaneously. In general, polarizable models have no distinct advantage in reproducing the structural and energetic properties of liquid water, but they allow for better treatment of dynamic properties. 

Since both molar volume and refractive index are influenced by the actual molecular species present in a solution, molar refraction has some potential value for studying association equilibria. Giles and co-workers (65-68) correlated the method with dielectric constant measurements, and have been the most active users of refractive index for studying compound formation. Reference 68 reviews earlier work (which is sketchy) and lists about forty systems (mostly oxygen containing compounds) that were studied. References 65-67 deal with amide, amine, and azo compounds, plus esters and additional work on alcohols, aldehydes, ketones, and carbohydrates. The method is simple the refractive index of a series of mixtures of varying composition but constant concentration in a solvent is measured. Compound formation is shown by a change in the slope of the n vs. mole fraction plot, such as in Fig. 2-15. 

The density of the foil samples was also measured in order to correlate the dielectric constant results with the density values. These density measurements were performed according to ASTM D1505-68 with the aid of a water/ethanol density gradient column at a temperature of 21.00°C + 0.01°C. 

Correlation of rates with dielectric constants has often been used as a method for determining whether aquations are primarily associative or dissociative in character. The mechanisms of aquation of cis- and trans-[CoBr(NCS)en2]+ and of [Cl(NH3)4Co-NH2 Co(NH3)4(OH2)] + (ref. 47), and of cis- and ra/zj-[CoCl(N3)en2]+ (ref. 48), have been investigated by this method. 

The correlation of E-p (SB), the semiempirical polarity parameter based on SB, and dielectric constant is not linear. Nearly linear correlation was obtained for mixtures of organic solvents with water with dielectric constants higher than 30 - 40. 

The squared refractive indexes of the -alkanes were used as dialectic constants (s, 25°Q in developing Eq. (40) which correlates molar dielectric constants with chain length. The indicated limiting dielectric constant... 

Correlations between log(D) and E , and between log(D) and CED were good. These results suggest that gas diffusivity is affected by the cohesive forces of polymers. Toi et al. and we have reported a correlation between log(D) and CED independently(9,35-37). Jia and Xu have reported correlations between gas permeability and a parameter which included contributions from both CED and Vf(38). CED depends on the square of the solubility parameter, which we treat as a total parameter with dispersive, polar, and hydrogen-bonding contributions. Van Krevelen(39) has indicated that a simple correlation between dielectric constant, 6, and CED is observed for polymers. This notion is expressed by Equation 11. 

Fig. 5.20. The shock-induced polarization of a range of ionic crystals is shown at a compression of about 30%. This maximum value is well correlated with cation radius, dielectric constant, and a factor thought to represent dielectric strength. A mechanically induced point defect generation and migration model is preferred for the effect (after Davison and Graham [79D01]).

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