Tetraalkylammonium Ions in Aqueous and Non-aqueous Solutions

Property data for tetraalkylammonium cations, [H(CH₂) _n ]₄N⁺, are reviewed. They pertain to the isolated cations and their transfer from the gas phase into aqueous solutions. Various properties of these cations in aqueous and non-aqueous solutions and data for their transfer between these are also reviewed. Emphasis is placed on the dependence of data on the length n of the alkyl chains rather than on the absolute values. Most of the data are available only for the first four members of the series. The properties of the isolated ions increase linearly with the chain length. Molar enthalpies of formation of the gaseous and aqueous cations, and absolute standard molar enthalpies of hydration, are derived. Standard molar entropies of dissolution of several salts in water are obtained from their solubilities and enthalpies of solution. The molar entropies of the crystalline iodides of the first four members of the series then give the standard partial molar entropies of the aqueous cations and their molar entropies of hydration. The standard partial molar volumes in aqueous and non-aqueous solutions are quite linear with n and in non-aqueous solutions the molar volume hardly depends on the nature of the solvent. On transfer from water to non-aqueous solvents the volume of Me₄N⁺ suffers some shrinkage, that of Et₄N⁺ appears to be unaffected, but from Pr₄N⁺ onwards an increasing expansion takes place. This unexpected result is tentatively explained by hydrophobic intra-molecular association of pairs of alkyl chains in aqueous solutions, resulting in a tightening of the structure. The transfer of the R₄N⁺ cations from water into non-aqueous solvents is governed by a large positive entropy change, outweighing the smaller positive enthalpy change. The transport properties of the aqueous R₄N⁺ cations are non-linear with n. A major impediment to movement is thus the sticking of the water molecules to the ice-like hydrophobic hydration sheaths of the larger cations. The number of water molecules affected by the hydrophobic cations is open to widely differing estimates resulting from various approaches, and constitute an open issue.     

Excess Molar Volumes of Aqueous Solutions of Butylamine Isomers

Abstract

Excess molar volumes (V^E ) and average thermal expansivities (α) of the systems, water (W) + n-butylamine (NBA), W + sec-butylamine (SBA), and W + tert-butylamine (TBA), have been calculated from the density data at temperatures ranging from 298.15–323.15 K. The V^E and α values have been plotted as functions of mole fraction of amines. The systems show large negative excess volumes, magnitude of which varies in the order, W + TBA > W + SBA > W + NBA. The curves are found to be symmetrical along the composition axis, with minima occurring at 0.5 mole fraction of butylamines. The negative excess volumes have been interpreted primarily by two effects: (i) strong chemical interaction leading to the formation of 1:1 complexes through H-bonding and (ii) hydrophobic hydration causing significant contraction of volume.     

Electrical Conductance Studies in Aqueous Solutions with Glutamic Ions

Conductivity measurements in dilute aqueous solutions of L-glutamic acid, DL-glutamic acid, sodium-L-glutamate and magnesium-L-glutamate, were performed in the 288.15 to 323.15 K temperature range. The limiting molar conductivities of glutamic anions, λ ^o(HGlu⁻,T) and the dissociation constants of glutamic acid, K ₂(T) were derived by the use of the Debye–Hückel equation for the activity coefficients and the Onsager, and Quint and Viallard conductivity equations.     

Electrical Conductance Studies in Aqueous Solutions with Aspartic Ions

Conductivity measurements of dilute aqueous solutions of DL-aspartic acid, potassium-DL-aspartate and magnesium-DL-aspartate were performed in the 288.15 to 323.15 K temperature range. The limiting molar conductances of aspartate anions, λ ⁰(HAsp⁻,T) and the dissociation constants of aspartic acid, K ₂(T) were derived by use of the Debye-Hückel equation for the activity coefficients and the Onsager, and Quint and Viallard conductivity equations.     

Electrical Conductance Studies in Aqueous Solutions with Ascorbate Ions

Conductivity measurements in dilute aqueous solutions of L-ascorbic acid, sodium-L-ascorbate, magnesium-L-ascorbate, calcium-L-ascorbate and ferrous-L-ascorbate were performed in the (288.15 to 323.15) K temperature range. The limiting molar conductances of the ascorbic anion, λ^∘(HAsc⁻, T), and the dissociation constants of ascorbic acid, K(T), were derived by the use of the Debye-Hückel equation for the activity coefficients and the Onsager and Quint and Viallard conductivity equations.     

Complexation of Calcium Ions with Dicarboxylic Acids in Aqueous Solutions

Complexation of calcium ion with malonic, succinic, glutaric, adipic acids at 25°C, ionic strength I = 0.3 (KCl) was studied by pH-potentiometric titration.     

The State of Copper Ions in Aqueous and Aqueous Ammonia Solutions of Copper Acetate

Stabilization of Cu²⁺ ions in aqueous and aqueous ammonia solutions of copper acetate was studied for a wide range of ammonia concentrations. The structure of copper acetate hydrate complexes was shown to markedly change upon dissolution in water. In aqueous solutions, copper is stabilized as strongly bound Cu²⁺ associates (dimers) in a distorted octahedral environment composed of water molecules and acetate groups oxygen atoms in equatorial positions with strong exchange interaction via acetate groups. In solutions of copper acetate in aqueous ammonia, the concentration of ammonia has a crucial effect on the ordering of Cu²⁺ ions in associates. At high ammonia concentration, disordered copper tetra-ammoniate associates with the \({d_{{x^2} - {y^2}}}\) ground state are formed, whereas at low ammonia concentration, bulky Cu²⁺ ion associate structures are generated, with the \({d_{{x^2} - {y^2}}}\) ground state, hydroxyl groups in the equatorial plane, and water molecules in the axial positions.     

Chitosan-Based Materials for the Removal of Nickel Ions from Aqueous Solutions

Russian Journal of Physical Chemistry A - Sorption of Ni(II) ions from liquid effluents utilizing chemically modified chitosan; (vanillin, polymer I) and (ortho-vanillin, polymer II) is studied...     

Electron Transport Properties of Ions in Aqueous Solutions of Sodium Selenite

Ion diffusion kinetics has been studied using the data of conductivity measurements for aqueous solutions of sodium selenite with different concentrations and at different temperatures. Molecular and ionic self-diffusion coefficients have been determined for infinitely dilute solutions in the temperature range 288 K-313 K. The limiting values of ion mobility and changes in the energies of translation of water molecules from ions’ hydration shell have been found. At elevated temperatures, ΔE _tr ⁰ increases for both ions in direct proportion to the crystallographic radius of the latter. Ion hydration numbers at 298 K have been calculated. The results of this study are interpreted in the light of Samoilov’s theory on positive and negative hydration of ions.Original Russian Text Copyright © 2004 by L. T. Vlaev and S. D. Genieva__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 870–876, September–October, 2004.     

Estimation of the Partial Molar Volumes of Ions in Mixed Electrolyte Solutions Using the Pitzer Equations

Journal of Solution Chemistry - The Pitzer equations have been shown to be very useful in estimating the physical chemical properties of mixed electrolyte solutions like seawater. The equations...     

Apparent Molar Volumes of Proline-Leucine Dipeptide in NaCl Aqueous Solutions at 318.15 K

Density measurements of pseudo-binary solutions of proline-leucine dipeptide in aqueous NaCl solutions with molality ranging from 0 to 1 mol-kg^–1 have been performed at 318.15 K. Apparent molar volumes, V_{, 2}, of proline-leucine were calculated from the measured data. Limiting partial molar volumes, V₂, and limiting partial molar volumes of transfer from water to aqueous NaCl solutions, _tr V₂, were derived and interpreted in terms of ion-dipeptide interactions and changes in the characteristics of the hydration shell around the biomolecules as well.     

Models for the Immediate Environment of Ions in Aqueous Solutions of Neodymium Chloride

Radial distribution functions of neodymium chloride aqueous solutions in a wide range of concentrations under ambient conditions are calculated from experimental data obtained earlier via X-ray diffraction analysis. Different models of the structural organization of the system are developed. The optimum versions are determined by calculating theoretical functions for each model and comparing their fit to the experimental functions. Such quantitative characteristics of the immediate environment of Nd³⁺ and Cl^? ions as coordination numbers, interparticle distances, and varieties of ion pairs are determined. It is shown that the average number of water molecules in the first coordination sphere of the cation falls from 9 to 6.2 as the concentration rises. The structure of the systems over the whole range of concentrations is determined by ion associates of the noncontact type.     

Apparent Molar Volumes of Symetric and Asymetric Tetraalkylammonium Salts in Dilute Aqueous Solutions

The apparent molar volumes, V_φ of tetramethylammonium, tetraethylammonium, tetrabutylammonium, butyltriethylammonium, dibutyldiethylammonium, and tributylethylammonium bromides have been measured at 298.15K in the concentration range from 0.01 to 0.04mol⋅kg⁻¹. The concentration dependence of V_φ is given using the Redlich and Meyer relation. The apparent molar volume at infinite dilution, V∘_φ, and the empirical constant, B_V, have been calculated. The CH₂-group contribution has been obtained by the additivity rule. The results were interpreted in terms of solute–solvent interactions.     

Sorption of Nickel Ions from Aqueous Solutions by Ion Exchangers

Sorption of Ni²⁺ions from aqueous solutions by ion exchangers differed in their chemical nature and structure was studied. Based on the endothermic curves of ice melting obtained by a differential scanning calorimetry, the amounts of freezing and non-freezing water present in free volumes (pores) of the studied ion exchangers were calculated. Comparison of results obtained from the kinetic curves of nickel ion sorption with data on differential scanning calorimetry indicates a role of structural factor in the sorption of nickel ions. It was found that, depending on the total amount of freezing and non-freezing water, the KU-2-8 sulfonated cationite is the most preferable ion exchanger for the sorption of nickel ions from aqueous solutions. Therefore, sorbent efficiency in this case is determined by its structure rather than by chemical nature.     

用Pitzer理论预测混合电解质溶液的偏摩尔体积

用Pitzer理论研究了混合电解质溶液的偏摩尔体积,建立了偏摩尔体积的预测方法,并利用所得电解质溶液的表观摩尔体积的Pitzer参数预测了HNO₃-UO₂(NO₃)₂-H₂O、KCl-Na₂SO₄-H₂O、NaCl-Na₂SO₄-H₂O、NaCl-CaCl₂-H₂O、KCl-CaCl₂-H₂O、KCl-MgCl₂-H₂O和KCl-NaBr-H₂O共7个系统4种类型的混合溶液的偏摩尔体积。     

Radiation Chemistry of Neptunium Ions in Aqueous Carbonate and Bicarbonate Solutions*

The radiolytic reactions of neptunium ions in aqueous carbonate, alkaline carbonate, and bicarbonate solutions were examined. It was found that Np(VI) is not oxidized to Np(VII) in carbonate and bicarbonate solutions saturated with nitrous oxide, whereas this oxidation process takes place in alkaline carbonate solutions, in which Np(VI) occurs as a hydroxo complex. It was also found that Np(V) is a radiation-stable neptunium species in carbonate solutions, whereas Np(VI) is stable in bicarbonate solutions.     

Partial Molal Volumes of Asymmetric Iodides of Butyl-Triethyl-Ammonium in Aqueous Solutions at 298,15 K

Abstract

Density measurements have been made on aqueous solutions of t-BuEt₃NI, s-BuEt₃NI, i-BuEt₃NI, Bu₄NI and Et₄NI at 298,15 K from 0,01 to 0,05 m. The apparent molal volumes V0₂ calculated from the V _2,? (m) plots for the salts show a decrease value: n-BuEt₃NI > i-BuEt₃NI > s-BuEt₃NI > t-BuEt₃NI. The data analysis may suggest that the cations with the butyl isomers perform two groups: n-BuEt₃N⁺ and i-BuEt₃N⁺ with the highest V ₂ ⁰, and t-BuEt₃N⁺ and s-BuEt₃N⁺ similar to Et₄N⁺ one. The peculiarities of the experimental observation may be interpreted as a consequence of the structural effect over the intermolecular forces that affect the solute-water interactions deeply.     

Complexation of Chlorodiethylenetriaminegold(III) with Chloride Ions in Aqueous Solutions

The reaction of Au(Dien)Cl²⁺ (Dien is diethylenetriamine) with the chloride ion was studied spectrophotometrically in an aqueous solution at I = 1.0 mol/l and T = 20°C. The formation constant of pentacoordinated Au(Dien)Cl ₂ ⁺ was determined and its spectrum was calculated.     

Complexation of Arabinogalactan with Copper(II) Ions in Aqueous Solutions

Complexation of Cu(II) with arabinogalactan as influenced by solution pH was studied by spectrophotometry and the method of dialysis equilibrium. Copper ions form complexes with arabinogalactan in a wide pH range, pH 5.0-12.5. Arabinogalactan forms two complex species with the metal. The composition and formation constant of the complex formed at pH <10.8 were determined.