Dielectric well logging

Recovery well recharge test Dielectric well logging tool Optoelectronic sensor... 

Keech, D. H., 1988, Hydrocarbon Thickness on Groundwater by Dielectric Well Logging In Proceedings of the National Water Well Association of Ground Water Scientists and Engineers and the American Petroleum Institute Conference on Petroleum Hydrocarbons and Organic Chemicals in Ground Water Prevention, Detection and Restoration, Vol. I, November, pp. 275-289. 

In the absence of charges and dipoles, short-range effects such as hydrogen bonding and hydrophobic hydration become important. The complex solute-solvent interactions in such cases, however, are not well understood. In addition there is the possibility of ion or ion-pair catalysis. Especially in cases with solvents of low dielectric constant, it has been observed that k3 rather than log k3 becomes linear in cs... 

The continuum model has been applied to an experimental study of the solvent effect on the 6-chloro-2-hydroxypyridine/6-chloro-2-pyridone equilibrium in a variety of essentially non-hydrogen-bonding solvents (Beak et al., 1980). In this study, a plot of log A nh/oh) versus (e - 1)/ (2e + 1), the solvent dielectric term, yielded a linear least-squares fit with a slope of 2.5 0.2, an intercept of -1.71, and a correlation coefficient of 0.9944. This result was used to estimate the gas phase free-energy difference of 9.2 kJ mole-1, which compares favorably with the observed value of 8.8 kJ mole-1 for this system. The authors also reported that alcohol solvents are correlated fairly well in this study but that other solvents seem to be divided into two classes, those that are electron-pair donors and those that are electron-pair acceptors in a hydrogen bond. The hydrogen bonding effect is assumed to be independent from the reaction field effect and is included in the continuum model by means of the Kamlet and Taft (1976) empirical parameters. The interested reader is referred to the original paper for a detailed discussion of the method and its application. 

In the presence of catalyst, the reaction is understood to occur via parallel paths with contributions from the uncatalyzed and catalyzed paths. The total rate constant (kT) is equal to the sum of the rate constants of the catalyzed (kC) and uncatalyzed (kU) reactions. Hence, kC=kT-kU. The reaction orders have been determined from the slopes of log kc versus log (concentration) plots by varying the concentration of L-trp, Os(VIII), OH-, and I04-, in turn, while keeping the other concentrations constant. The order in both [DPC] and [Os(Vlll)j was found to be unity. The order in [L-trp] and [OH-] was found to be less than unity, and in [periodate] to be negative and less than unity. It is well known that [9] Os(VIII) exists as (0s04(0H)2]2+ in aqueous alkaline medium. It was found that the increase in ionic strength increased the rate of reaction and decrease in dielectric constant of the medium increased the rate of reaction. Initially added products did not have any significant effect on the rate of reaction. Test for free radicals indicated the participation of free radical in the reaction [6]. These experimentally determined orders and results could be well accommodated in Scheme 2. 

Kakiuchi and Endo studied the influence of the nature of the solvent on the pyridine-catalyzed reaction of benzoic acid with l,2-epoxy-3-phenoxypropane. The reaction is first order for acid, epoxide, and catalyst it was carried out in toluene-nitrobenzene and in toluene-dioxane mixtures as well as in different pure solvents. The dielectric constant was measured before the reaction started and after the reaction stopped it was noted that this constant hardly changes during the course of the reaction. A linear relationship between log q and D was dbserved in toluene-nitrobenzene, but not in dioxane-nitrobenzene according to the authors, this could be due to a specific solvating effect of dioxane. 

These conclusions are also consistent with the solvent dependence [33] of kf in solvents of dielectric constant 2 to 10. It is found that the values of log kf correlate well with the solvent polarity parameter Ej, indicating that the proton-transfer process is dominated by solvent reorganization rather than by the actual movement of the proton. 

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