Abstract:-The UNIQUAC model for the excess Gibbs energy is modified using chemical theory to account for chain-like association occurring in self-associating compounds such as alcohols. The equation considers the alcohol to be a mixture of clusters in chemical equilibrium. The UNIQUAC equation is used to model the behavior of the mixture of clusters, with size and surface parameters related to the number of alcohol molecules involved in their formation. The values of association enthalpy and entropy were obtained throu… Show more
1 H NMR measurements indicate that (X-pyridyl)alkanols of the general formula (C 5 H 4 N)(CH 2 ) n OH, where n ¼ 1, 2 or 3, self-associate as open dimers, cyclic dimers, trimers and tetramers, with considerable variations depending on the position of the alkyl chain and its length. 2-(X-Pyridyl)propan-2-ols behave like the corresponding pyridylmethanols with, however, somewhat lower association constants. The IR spectra of 3-(X-pyridyl)-2,2,4,4tetramethylpentan-3-ols (X ¼ 3 or 4) in carbon tetrachloride suggest weak association, while the 2-pyridyl derivative occurs mainly as the intramolecularly hydrogen-bonded rotamer. The OH NMR shifts for the 3-and 4-pyridyl derivatives in benzene are concentration-dependent, but neither the equilibrium constants nor the degree of association can be evaluated. Benzyl alcohol in benzene associates as an open dimer and a cyclic tetramer, as does 2phenylpropan-2-ol, only more weakly. Rotation barriers for 3-(X-pyridyl)-2,2,4,4-tetramethylpentan-3-ols (X ¼ 2, 3 or 4) in DMSO or nitrobenzene are 20-21 kcal mol À1 .
1 H NMR measurements indicate that (X-pyridyl)alkanols of the general formula (C 5 H 4 N)(CH 2 ) n OH, where n ¼ 1, 2 or 3, self-associate as open dimers, cyclic dimers, trimers and tetramers, with considerable variations depending on the position of the alkyl chain and its length. 2-(X-Pyridyl)propan-2-ols behave like the corresponding pyridylmethanols with, however, somewhat lower association constants. The IR spectra of 3-(X-pyridyl)-2,2,4,4tetramethylpentan-3-ols (X ¼ 3 or 4) in carbon tetrachloride suggest weak association, while the 2-pyridyl derivative occurs mainly as the intramolecularly hydrogen-bonded rotamer. The OH NMR shifts for the 3-and 4-pyridyl derivatives in benzene are concentration-dependent, but neither the equilibrium constants nor the degree of association can be evaluated. Benzyl alcohol in benzene associates as an open dimer and a cyclic tetramer, as does 2phenylpropan-2-ol, only more weakly. Rotation barriers for 3-(X-pyridyl)-2,2,4,4-tetramethylpentan-3-ols (X ¼ 2, 3 or 4) in DMSO or nitrobenzene are 20-21 kcal mol À1 .
Most of what is known about the environmental fate and transport of contaminants comes from studies of dilute, aqueous solutions. Theoretical and practical aspects of hydrophobic organic contaminants in aqueous mixtures of organic solvents are well developed, but relatively little attention has been paid to those situations where inorganic contaminants such as metals, water, and organic solvents occur simultaneously. The authors discuss changes in solution properties accompanying the addition of organic solvents. They review more than 500 references to available data on ion solvation, solubility, activity, acidity, pairing, and pH in electrolyte and electrolyte-free solvent mixtures and tabulate selected experimental values. Whenever available, equations developed to estimate these properties are given and their applications and limitations described. The implications of the progress in mixed-solvents solution chemistry on contaminant behavior and transport are described. Major limitations to the study of inorganic contamination in mixed solvents include the absence of complete and comprehensive data (e.g., type of ionic species, activity coefficients, solubility constants) that characterize solute and solvent properties in these mixtures and the indefinite number of possible solute and solvent combinations. The generation of models predicting such data from easily measured benchmark solute and solvent properties is a major challenge. The availability of such database and models may open the field for environmental engineers and soil scientists to study the basic chemical processes and mechanisms of metal contamination in complex multicomponent systems.
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