Sulfolane constant

Electronic and Electrical Applications. Sulfolane has been tested quite extensively as the solvent in batteries (qv), particularly for lithium batteries. This is because of its high dielectric constant, low volatUity, exceUent solubilizing characteristics, and aprotic nature. These batteries usuaUy consist of anode, cathode polymeric material, aprotic solvent (sulfolane), and ionizable salt (145—156). Sulfolane has also been patented for use in a wide variety of other electronic and electrical appHcations, eg, as a coil-insulating component, solvent in electronic display devices, as capacitor impregnants, and as a solvent in electroplating baths (157—161). 

The dissociation is much more favoured in DMSO than in sulfolane, in spite of the magnitude of their dielectric constants which are almost identical, i.e. 46.68 and 43.3, respectively. The favourable dissociation,could be ascribed to extraordinarily strong solvation by DMSO around the cations... 

On the basis of the results in acetonitrile, it might be reasonable to assume that the values for A//het(R-R ) and AG°het(R-R ) are apparently close to each other also in sulfolane, since the dielectric constant (43.3) and the donor number (14.8) of this solvent are close to those of acetonitrile (37.5 and 14.1, respectively). On the basis of this assumption, Arnett s equation (28) was examined for reactions of type (23). For these reactions, except for [3-2], only the AGhet(R-R ) values are avtiilable. As shown in Fig. 3, the values for this system are about 10 kcal moP less than predicted from (28). The negative deviation can also be ascribed to steric congestion in these hydrocarbon molecules. The large negative deviations, similar to those observed in sulfolane, are also seen in Fig. 3 for the values of AGSet(R-R ) in DMSO. 

Rate constants for ionization of carbon acids (chloroform-r and acetophenone-r) in alkaline aqueous sulfolane have been determined and their dependence on solvent composition and temperature has been interpreted for this highly basic medium. °... 

The acidity constants of HNO3 and HNOj are the following pK lMNOj) = 16.0 and pK (HNOj) = 20.6 at 30°C in sulfolane (Boughriet et al. 1987). The authors deduced the equilibrium constants (K) for N2O4 and NjOj reactions ... 

This approach applies only when we are certain that the substrate is mainly in the form of the free ion at the lowest anion concentrations. This is true in the chloride exchange of cw-[Co en2 Cl2]+ in methanol and we can safely conclude that the mechanism is unimolecular (8, 9. 10, 11, 26, 27). This condition did not exist when we studied the displacement of water in trans-[Co en2N02H20]+2 by anions where, because of the large ion association constants, none of the substrate was in the free ion form under reaction conditions. However, in the reaction between trans-[Co en2N02Br]+ and thiocyanate in sulfolane, the substrate was mainly in the free ion form. The observed second-order kinetic form was fully consistent with assigning a bimolecular mechanism to the rearrangement of the ion pair. 

Another method of reducing ion pairing is to use a solvent having a high dielectric constant, such as sulfolane ... 

This material has a dielectric constant of 43.3 at 30UC it has very low proton basicity (pA, = — 12.9) and is a weak Lewis base (117). Indeed, sulfolane is an excellent solvent for the rhodium catalytic system, giving good rates... 

Here, c is the total concentration of MA, KA is the association constant, a is the degree of dissociation of the ion-pair M2+A2h and y is the average activity coefficient of free ions of concentration ca. Because the ion-pairs do not conduct electricity, the molar conductivity A in the presence of ion association is less than in its absence. In Fig. 7.1, the difference between the experimental molar conductivity (A) and the value calculated from Eq. (7.1), /lcai, are plotted against c1/2 for lithium halides in sulfolane [la]. For Lil, the difference between A and /lcai is small because ion association is not appreciable (KA=5.(> mol-11). For LiBr (KA = 278 mol-11) and LiCl (KA= 13860 mol-11), however, A is much smaller than... 

The changes in the o-Ps lifetimes should be explainable on the basis of eq. (10) and its connection with the free volume. It is interesting to note that in sulfolan, the latter does not change at the liquid/plastic phase transition. The changes in I3 cannot yet be quantified. Changes in the dielectric constant (in the Onsager radius) should be one of the main factors to consider. 

Intrinsic defects in molecular solids. Figure 4.14 shows the variations of r3 with T in succinonitrile [125, 129]. As sulfolan, this compound exhibits a brittle (monoclinic) phase up to 233 K, then a plastic body-centered cubic phase. The phase transition is well evidenced, with some hysteresis. However, above the phase transition point, x3 increases further in a sigmoidal way characteristic of defect formation. By using Eq. (24), the activation energy of the intrinsic molecular defect is obtained (0.36 eV). Analyzing the PALS spectra in four components confirms that x3 does represent the average between an o-Ps bulk lifetime, which decreases with T, and the constant lifetime of o-Ps trapped in the vacancies whose intensity increases with T. 

Conductometric and spectrophotometric behavior of several electrolytes in binary mixtures of sulfolane with water, methanol, ethanol, and tert-butanol was studied. In water-sulfolane, ionic Walden products are discussed in terms of solvent structural effects and ion-solvent interactions. In these mixtures alkali chlorides and hydrochloric acid show ionic association despite the high value of dielectric constants. Association of LiCl, very high in sulfolane, decreases when methanol is added although the dielectric constant decreases. Picric acid in ethanol-sulfolane and tert-butanol-sulfolane behaves similarly. These findings were interpreted by assuming that ionic association is mainly affected by solute-solvent interactions rather than by electrostatics. Hydrochloric and picric acids in sulfolane form complex species HCl and Pi(HPi). ... 

Conductivity. The conductivity bridge has been described (6). A 0.01000M standard KC1 solution was used to calibrate the Beckman conductivity cell. A value of 0.488 cm"1 was obtained for the cell constant. Measurements were made at 30°C on 50 ml of 0.1-0.5M acid solutions in sulfolane with successive additions of water or ether from a 2-ml Teflon glass syringe. All acid solutions were processed in a glove box. 

Concerning the nature of HSbCl6 solutions in sulfolane, we have reported (7) that adding SbCl5 (1) to weakly conducting solutions of HC1 leads to an initial linear increase of L with C Sbci5 and an extrapolated value of A0 near 11.5 O 1 cm2 equiv"1. We took this to indicate that the equilibrium constant JCf for Reaction 1 is large... 

Fig. 6. Dependence of the logarithm of the standard rate constant of phenothiazine oxidation on a Ft electrode on the logarithm of the solvent s longitudinal relaxation time. NE, nitroethane TMS, sulfolane. For other abbreviations see 1k-blel.

Useful solvents must themselves resist oxidation or reduction, should dissolve suitable ionic solutes and nonelectrolytes, and in addition should be inexpensive and obtainable in high purity. Kratochvil indicated that the most potentially useful solvents are those that have a dielectric constant greater than about 25 and have Lewis-base properties. Some solvents meeting these criteria are acetonitrile, dimethyl-sulfoxide, dimethylformamide, dimethylacetamide, propylene carbonate, ethylene carbonate, formamide, sulfolane, and y-butyrolactone. Solvents of the Lewis-base type show specific solvation effects with many metal cations (Lewis acids). Thus acetonitrile functions as a Lewis base toward the silver ion. At the same time it reacts but little with the hydrogen ion. 

The effects of Al-aryl substituents on rate constants for the quaternization of imidazoles can be correlated using a Hammett equation. It has been shown that the rates for quaternization of N-arylpyrazoles with dimethyl sulfate in sulfolane show greater steric and substituent effects than in the... 

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