Dielectric behavior 2026 alcohols

Onsager Theory for C(t) for Non-Debye Solvents. Generally solvents have more complex dielectric responses than described by the Debye equation (Eq. (18)). To obtain the time dependence of the reaction field R from Eqs. (12, (15), (16) and (7) an appropriate model for dielectric behavior of a specific liquid should be employed. One of the most common dielectric relaxation is given by the Debye-type form, which is applicable to normal alcohols. 

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. 

Statistical mechanicsd theory of dielectric behavior applied to water, alcohols and others. 

The conductive and dielectric behavior of water-in-oil, (w/o), type transparent isotropic systems using either non-ionic surfactants or a combination of an ionic surfactant with a medium chain-length alcohol used as the cosurfactant was investigated between 400 Hz and 2 GHz or so. 

Another approach used in the empirical characterization of liquid polarity is the study of the outcome of a chemical reaction. Earle et al. [216] report a preliminary study of the keto-enol tautomerization of pentane-2,4-dione, and create an empirical correlation between the degree of tautomerization and the dielectric constant of molecular liquids. They then predict dielectric constants for a series of ILs based on the observed keto-enol equilibrium the values range from 40 to 50, slightly higher than those of short-chain alcohols. A more detailed study by Angelini et al. [217] considers the tautomerization of a nitroketone complex in a series of five imidazolium-based ILs. The results, parameterized as a linear free energy analysis of the behavior of the equilibrium constant, indicates an overall polarity comparable to that of acetonitrile, consistent with the partitioning and spectroscopic studies referenced above. 

Similar anomalous kinetic behavior in alcohols was observed for other systems as well [148, 173]. Weaver and coworkers [3] discussed this behavior, considering the influence of high-frequency dielectric relaxation associated with rotation of solvent monomers and with translational motion of solvent dipoles. 

The situation is more complex in the case of the so-called non-Debye liquids -the protic solvents. Due to their internal structure, these liquids exhibit a complicated dielectric relaxation behavior. This group of solvents comprises alcohols, formamide, propylene carbonate, and some other liquids. One should remember that in the In vs. In Tl analysis (Sec. 3.1.3), the rate constants measured in these solvents deviated from the values measured in aprotic solvents. 

The plot shows a distribution closely around a slope of unity indicated by the solid line in Figure 2 except for the alcohols and nitrobenzene. Such anomaly in alcohols is also reported for other chemical processes and time-dependent fluorescence stokes shifts and is attributed to their non-Debye multiple relaxation behavior " the shorter relaxation components, which are assigned to local motions such as the OH group reorientation, contribute the friction for the barrier crossing rather than the slower main relaxation component, which corresponds to the longitudinal dielectric relaxation time, tl, when one regards the solvent as a Debye dielectric medium. If one takes account of the multiple relaxation of the alcohols, the theoretical ket (or v,i) values inaease and approach to the trend of the other solvents. (See open circles in Figure 2.)... 

A second type of study that corroborates the basic assumption is any measurement which specifically shows that the H bonded species are cyclic. Infrared data can offer such evidence, provided the only important species over a wide concentration range are monomers and dimers. For such a system the peak intensities of absorption by the monomer (Im) and dimer (Id) are simply related the ratio IdIIm is a constant. Such behavior has been observed and cited in favor of cyclic dimers of S-valerolactam and of -caprolactam by Tsuboi (2050), and of y-bu-tyrolactam by Klemperer et al. (1117). However, no such deduction can be made for other amides (e.g., see 1117), phenols (e.g., see 411), or alcohols (e.g., see 1375 and 1150). There is much evidence in favor of cyclic dimers of carboxylic acids in the gas phase (1081), and some referring to solutions (1652 and 445). On the other hand, the IR data for liquid formic acid are more complicated. Ghapman (373) concludes that the liquid contains a mixture of cyclic dimers and chain polymers. Dielectric data have been interpreted to show that formic acid is not entirely dimeric (1046). By use of thermo-electric osmometry Davies and Thomas have measured AH of dimerization of several amides and have concluded that trichloroacetamide and A -methyltrichloroacet-amide form cyclic dimers, whereeis iV-methylaceteunide, iV-methylform-... 

The field dependence of the dielectric constant is known as the dielectric saturation effect (DSE), and in an unassociated medium A e/E2 increases linearly with concentration. Malecki (20) has found that in alcohol solutions considerable nonlinearities occur—positive saturation is obtained at low concentrations and negative at high concentrations. This behavior is interpreted according to the theory of Piekara (22), and for 1-hexanol in hexane Malecki shows that the degree of association increases with increasing concentration. 

Abou-Aiad, T.H.M., Abd-El-Nour, K.N., Hakim, l.K. and Elsabee, M.Z. (2005) Dielectric and interaction behavior of chitosan/polyvinyl alcohol and chitosan/polyvinyl pyrrolidone blends with some antimicrobial activities. Polymer, 47, 379-389. 

The abihty to form hydrogen bond networks is related to increased dielectric constants, with increases in the hydrogen bond donor property of the cation and the hydrogen bond acceptor property of the anion giving higher e. values. This is similar to the behavior of, for example, molecular alcohols. 

A tenside with a relatively strong lipophilic group and weak hydrophilic group is mainly soluble in oil and preferentially stabilizes a w/o emulsion, and vice versa. This fact led to the development of a standard with which the relative strength or activity of the hydrophilic and lipophilic groups of emulsifiers can be evaluated. It is called the HLB value (hydrophilic-lipophilic balance). It can be determined, e. g., from dielectric constants or from the chromatographic behavior of the surface-active substance. The HLB value of the fatty acid esters of polyhydroxy alcohols can also be calculated as follows (SV =... 

As in S-PS solutions in polar solvent, a polyelectrolyte behavior was evidenced [59,69,70]. In alcoholic solutions, the effect was found to decrease with increasing solvent chain length due to the decrease of the dielectric constant [70]. The most important effect was found in dimethylacetamide solutions (a = 38), but it was surprising to find only a small effect in water solutions and no effect at all in amide solvents of dielectric constants larger than 100. Such a result was also evidenced in S-PS solutions [35]. Two explanations can be proposed either the effect occurs at lower concentration or the extension in such solvent is already maximum. 

It is proposed that the alcohol-induced formation of small areas of the interdigitated state near the GMi can cause the hyperpolarization of the neuronal membrane by infusion of Cl ions, which elicits the behavioral effects of alcohols. Interdigitation could promote dielectric breakdown of the membrane or the induction of a conformational change in the ionophore protein such that ions can permeate the membrane. In either case, only a few ion-conducting sites need be activated for hyperpolarization to occur. Induction of increased permeability of metabolites across membranes has been demonstrated for the antibiotic polymyxin . It has also been shown that polymyxin induces interdigitation i. 

The increase in temperature enhances the dissociation of water and leads to a decrease in its acidity scale (defined by — log Ke). The strength of acids and bases is therefore appreciably modified compared with normal conditions. Concurrent with the decrease in the dielectric constant of the medium, the effect of hydrothermal conditions on the behavior of acid-base couples of the type HA/A and may therefore be very different. This is the case for solvents such as water or alcohol, for example [43). This explains why (he basicity of the chlorine ion is much higher under hydrothermal conditions. In water at 500°C and 2kbar, the equilibrium constant of... 

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