Aqueous Mixtures Of Acetonitrile Research Articles

Transfer Free Energies of Fluoride Ion in Aqueous Mixtures of Some Organic Solvents

Abstract Standard free energies of transfer, ΔGt°, of potassium fluoride (KF) from water to aqueous mixtures of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), acetonitrile (ACN), 1,2-dimethoxyethane (DME), and 2-methoxyethanol (ME) have been determined at 25 °C from emf measurements performed on the double cell: Pb(Hg)–PbF2/KF(m), solvent/K(Hg)/KF(m), water/PbF2–Pb(Hg). ΔGt° values of F− were obtained from these values using the corresponding values of K+, as obtained earlier by use of tetraphenylarsonium tetraphenylborate reference electrolyte assumption. In each solvent system ΔGt°(F−) values are found to be increasingly positive with cosolvent composition reflecting the pronounced destabilization of F− and their relative order : DME>DMSO≥DMF>>ACN≈ME conforms to what is expected from the relative ‘aproticity’ of the dipolar aprotic cosolvents and that induced in the protic ME by the possible intramolecular H-bonding. The observed larger destabilization of F− compared to OH− in ME–water system has been attributed to the H-bonding effect of the protic cosolvent ME and the reverse behaviour in DME–water and DMSO–water systems to the absence of such effect of these cosolvents. Moreover, tests of Feakins-type extrapolation for assigning individual ion contribution using ΔGt°(KF) values along with those of other potassium halides, provided some important reflections on the inadequacy of such plots made without the data points of F−.

Distribution equilibria of solvent components in reversed-phase liquid chromatographic columns and relationship with the mobile phase volume

Various experimental methods for measuring the adsorption of solvent components from a mixed mobile phase in a liquid-solid chromatographic column are discussed in terms of the surface excess description. The adsorption from aqueous mixtures of acetonitrile and methanol on to reversed-phase packings was measured. As the derivation of individual isotherms for both solvent components from these data is impossible, two models for the adsorption process, viz., exclusive adsorption of organic modifier and adsorption of a mixture of constant composition, are discussed. The former model is discarded, partly because it cannot explain the occurrence of an azeotropic point. The second model can explain the data over a limited range of mobile phase compositions. The discussion shows that simple experimental estimates of the mobile phase (zero) volume, such as the retention volumes of a mobile phase disturbance or of isotopically substituted solvent components, are in general unreliable. Their validity under certain conditions can be argued only from the full adsorption isotherm, accepting specific assumptions about the adsorption process

The kinetics of aquation of cis-ammine-bromobis(ethylenediamine) cobalt(III) ion in water-organic mixtures

The aquation kinetics of cis-[CoNH 3Br(en) 2] 2+ were investigated in aqueous mixtures of ethyl alcohol, isopropyl alcohol, t-butylalcohol and acetonitrile. The rate constants, activation enthalpies and entropies were determined. The interpretation of the experimental data, based on electrostatic theory, was possible only when methyl alcohol and ethyl alcohol were used as co-solvents. It was shown that in the mechanism of reaction studied non-electrostatic interactions play an important role.

Effect of water as a proton donor on the decay of anthracene and naphthalene anion radicals in aqueous mixtures of acetonitrile, dimethylformamide, and dimethyl sulfoxide

Effect of water as a proton donor on the decay of anthracene and naphthalene anion radicals in aqueous mixtures of acetonitrile, dimethylformamide, and dimethyl sulfoxide

Polarographic study of the electrode reaction of cobalt(II) in aqueous and non-aqueous media

The reduction of cobalt(II) at the dme has been studied in water and aqueous mixtures of formamide, dimethylformamide and acetonitrile. In water the study was carried out in various complexing and non-complexing supporting electrolytes. The kinetic parameters have been calculated by Koutecky's method. The reversibility is in the order SO 4 2− > Br − > CO 4 − > Cl −. The addition on non-aqueous solvent increases the reversibility and rate constant values of the reaction and changes the E 1 2 to more positive values. The change of polarographic characteristics and kinetic parameters is explained in terms of solvation of the metal ion in these solvents.

N.M.R. studies of electrolytes in binary solvent mixtures

An N.M.R. study of AlCl3, TiCl4 and paramagnetic CoCl2 in water and in aqueous mixtures of acetone, acetonitrile, dimethylacetamide, N,N-dimethylformamide, dimethylsulphoxide, dioxane, ethanol, methanol, N-methylformamide, tetrahydrofuran, and tetramethylurea over a solvent range has been completed. The chemical shift results indicate that although water solvates ions extensively in all the mixtures, many of the organic components, particularly DMSO and the amides, compete effectively with water for added electrolyte. The diamagnetic and the paramagnetic solution results indicate that solvating ability decreases in the order DMSO > alcohols, amides > TMU, THF > acetone, acetonitrile, dioxane. This order correlates well with the basicities of these compounds but not with their dipole moments or dielectric constants.