Skip to main content
main-content

Über dieses Buch

Most organic molecules retain their integrity when dissolved, and even though in such cases the effects exerted by solvents are, in the language of the coordination chemist, of the "outer sphere" kind, the choice of solvent can be critical to the successful outcome of an operation or preparation. Solubilities of reactants and products must be taken into account, and even if the organic principals in the reactions retain their integrity, many of the reagents are electrolytes, and their state of aggregation will affect their reactivity. In testifying to the importance of understanding solute-solvent interactions I draw attention to a large class of inorganic species for which the involvement in the chemical and physical properties by the solvent is even more deeply seated. It is comprised by the large body of metal atoms in low oxidation states for which solvent molecules intervene as reagents. At the same time, because the ions carry charges, the effects arising from outer sphere interactions are usually greater than they are for neutral molecules. To cite an example: when FeCb(s) is dissolved in water to form a dilute - say O. OlO- solution there is a complete reorganization of the coordination sphere of the cation. Whereas in the solid each cation is surrounded by six chloride ions, in the solution the dominant form is [Fe(H20)6]3+ followed by [Fe(H20)sCI]2+, [Fe(H20)4CI2]+, etc. in rapidly decreasing abundance.

Inhaltsverzeichnis

Frontmatter

Ionic Solvation in Aqueous and Nonaqueous Solutions

Summary
The history of studies on ionic solvation is briefly reviewed, and structural and dynamic properties of solvated ions in aqueous and nonaqueous solutions are discussed. An emphasis is placed on ionic solvation in nonaqueous mixed solvents in which preferential solvation of ions takes place. A new parameter for expressing the degree of preferential solvation of an ion is proposed.
Hitoshi Ohtaki

Spin Equilibrium in Solutions

Summary
The newer literature on spin equilibria of Fe(II) complexes in solution is reviewed. The thermodynamics as well as the kinetics in different solvents are discussed.
Hans Toftlund

Invited Review Thermochromism and Solvatochromism in Solution

Summary
The thermochromic behaviour of various coordination compounds in solution is discussed, with a special focus on cyclic diamine chelates. Thermally induced spin-crossover phenomena of iron(II) complexes are also considered. The solvatochromic behaviour of mixed-ligand complexes is presented in detail.
Usama El-Ayaan, Fumiko Murata, Yutaka Fukuda

Recent Advances in the Description of the Structure of Water, the Hydrophobic Effect, and the Like-Dissolves-Like Rule

Summary
Following a critical survey of the vast recent literature, the state of the art may be summarized as follows:
Roland Schmid

Thermodynamic Investigation of Phase Equilibria in Metal Carbonate-Water-Carbon Dioxide Systems

Summary
Solubility measurements as a function of temperature have been shown to be a powerful tool for the determination of thermodynamic properties of sparingly-soluble transition metal carbonates. In contrast to calorimetric methods, such as solution calorimetry or drop calorimetry, the evaluation of solubility data avoids many systematic errors, yielding the enthalpy of solution at 298.15 K with an estimated uncertainty of ±3kJ·mol -1. A comprehensive set of thermodynamic data for otavite (CdCO3), smithsonite (ZnCO3), hydrozincite (Zn5(OH)6(CO3)2), malachite (Cu2(OH)2CO3), azurite (Cu3(OH)2(CO3)2), and siderite (FeCO3) was derived. Literature values for the standard enthalpy of formation of malachite and azurite were disproved by these solubility experiments, and revised values are recommended. In the case of siderite, data for the standard enthalpy of formation given by various data bases deviate from each other by more than 10 kJ • mor1 which can be attributed to a discrepancy in the auxiliary data for the Fee+ ion, A critical evaluation of solubility data from various literature sources results in an optimized value for the standard enthalpy of formation for siderite. The Davies approximation, the specific ion-interaction theory, and the Pitzer concept are used for the extrapolation of the solubility constants to zero ionic strength in order to obtain standard thermodynamic properties valid at infinite dilution, T = 298.15 K, and p =105 Pa. The application of these electrolyte models to both homogeneous and heterogeneous (solid-solute) equilibria in aqueous solution is reviewed. A comprehensive set of thermodynamic data of otavite (CdCO3), smithsonite (ZnCO3), hydrozincite (Zn5(OH)6(CO3)2), malachite (Cu2(OH)2(CO3) azurite (Cu3(OH)2(CO3)2) and siderite (FeCO3) was derived. Literature values for the standard enthalpy of formation of malachite and azurite were disproved by the solubility experiments, and reviced values are recommended. In the case of siderite, data for the standard enthalpy of formation given various data bases deviate from each other by more than 10kJ · mol-1 which can be attributed to discrepancy in the auxiliary data for the Fe2+ ion. A critical evaluation of solubility data from various literature sources results in an optimized value for the standard enthalphy of formation for siderite. The Davies approximation, the specific ion-interaction theory, and the Pitzer concept are used for the extrapolation of the solubility constants to zero ionic strength in order to obtain standard thermodynamic properties valid at infinite dilution, T = 298.15K, and p = 105 Pa. The application of these electrolyte models to both homogeneous and heterogeneous (solid-solute)equilibria in aqueous solution is reviewed.
Wolfgang Preis, Heinz Gamsjäger

The Solvent-Like Nature of Silica Particles in Organic Solvents

Abstract
Kamlet-Taft’s a (hydrogen bond donor acidity) and π*(dipolarizability) values of various silica batches measured in various solvents are presented. The α and π*parameters for the various solid acids are analyzed by means of Fe(phen)2(CN)2(cis-dicyano-bis-(1,10)-phenanthrolineiron(II), 1), Michler’s ketone (4,4’-bis-(dimethylamino)-benzophenone, 2), and two hydrophilic derivatives of 2, (4-(dimethylamino)-4’-(di-2-hydroxyethyl)-amino-benzophenone(3a) and 4,4’-bis(di-(2-hydroxyethyl)-amino)-benzophenone (3b) as well as coumarin 153 (4) as solvatochromic surface polarity indicators. Apparent β (hydrogen bond acceptor basicity) parameters for bare silica have been evaluated by means of an aminobenzodifuranone dye (5) as solvatochromic probe.
The chemical interpretation of the α and π*parameters and the nature of the solvent/surface interaction which they reflect are discussed. It can be shown that an increase of the HBA (hydrogen bond accepting) capacity of the solvent significantly decreases the HBD (hydrogen bond donating) capacity of the surface environment, whereas the dipolarity/polarizability value of the silica/solvent interface is a composite of many effects. The classification of the polarity of silica particles in organic solvents compared to pure liquids is outlined.
Theoretical ET (30) values of the solid/solvent interfaces are calculated by applying linear solvation energy (LSE) relationships using the independently measured a and π* values of the solid acids according to ET (30) = (ET (30))0+ aα +sπ*.
Yvonne Zimmermann, Mohamed El-Sayed, Silvio Prause, Stefan Spange

Prediction of Electrolyte Solubilities from Minimal Thermodynamic Information

Summary
A method is proposed that permits the proper extrapolation of thermodynamic quantities represented by the Pitzer equations from 25°C to other temperatures. The new method, which assumes temperature independent heat capacities, was tested for the NaCI—H2O system and found very satisfactory. A new evaluation of the Na2CO3—H2O system according to the CALPHAD method is presented, and solubilities for the quaternary Na2CO3—NaC1—NaOH—H2O and its ternary subsystems are predicted. Limitations of (i) these predictions and of (ii) the Pitzer model regarding extrapolations to high molalities are discussed.
Erich Königsberger

Preferential Solvation in Mixed Solvents X. Completely Miscible Aqueous Co-Solvent Binary Mixtures at 298.15 K

Summary
The Kirkwood-Buff integrals for 18 completely miscible aqueous co-solvent binary mixtures have been recalculated from thermodynamic data, and the volume-corrected preferential solvation parameters derived from them are presented. Also presented are these latter quantities for 15 additional such mixtures, for which the volume correction has not been applied previously. The self-interaction of the water, the mutual interaction of the water and the co-solvent, and the self-interaction of the co-solvent at infinite dilution derived from these integrals and parameters are then discussed. The systems studied include aqueous hydrogen peroxide, methanol, ethanol, 1- and 2-propanol, 2-methyl-2-propanol, 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoro-2-propanol, ethane-1,2-diol, glycerol, 2-methoxyethanol (at 313 and 343 K), 2-ethoxyethanol, 2-butoxyethanol, 2-aminoethanol, N-methyl-and N,N-dimethyl-2-aminoethanol, tetrahydrofuran, 1,4-dioxane, acetone, formic, acetic, and propanoic acids, piperidine, pyridine, acetonitrile, formamide, N-methyl-and N,N-dimethylformamide, N-methylacetamide, N-methylpyrrolidin-2-one (at 303 K), hexamethyl phosphoric triamide, dimethylsulfoxide, and tetramethylenesulfone (at 303 K).
Yizhak Marcus

Phase Transitions and Critical Behaviour of Binary Liquid Mixtures

Summary
Compared to the simple one-component case, the phase behaviour of binary liquid mixtures shows an incredibly rich variety of phenomena. In this contribution we restrict ourselves to so-called binary symmetric mixtures, i.e. where like-particle interactions are equal (Φ 11(r) = Φ22(r)), whereas the interactions between unlike fluid particles differ from those of likes ones (Φ 11(r)≠Φ 12(r)). Using both the simple mean spherical approximation and the more sophisticated self-consistent Ornstein-Zernike approximation, we have calculated the structural and thermodynamic properties of such a system and determine phase diagrams, paying particular attention to the critical behaviour (critical and tricritical points, critical end points). We then study the thermodynamic properties of the same binary mixture when it is in thermal equilibrium with a disordered porous matrix which we have realized by a frozen configuration of equally sized particles. We observe — in qualitative agreement with experiment — that already a minute matrix density is able to lead to drastic changes in the phase behaviour of the fluid. We systematically investigate the influence of the external system parameters (due to the matrix properties and the fluid—matrix interactions) and of the internal system parameters (due to the fluid properties) on the phase diagram.
Gerhard Kahl, Elisabeth Schöll-Paschinger, Andreas Lang

Extraction of Unprotected Amino Acids by Mixed-Ligand Nickel(II) and Copper(II) Chelates

Summary
Six mixed-ligand Nickel(II) and Copper(II) chelates with square-planar geometry of the formula [Ni/Cu(O-0)(S-tmpn)]B(C6H5)4 were prepared, where O-O represents acetylacetonate, tropolonate, or hinokitiolate and S-tmpn is (S)-tetramethyl-1,2-propanediamine. The compounds were investigated with respect to their function as receptor for unprotected amino acids, taking advantage of their high solubilities in non-polar organic solvents. In liquid-liquid extraction experiments between a 1,2-dichloroethane phase containing the metal chelates and an aqueous phase containing amino acids (rac-phenylglycine, rac-phenylalanine, or rac-tryptophan), the nickel(II) chelates effectively extracted amino acids from the aqueous phases under neutral conditions, forming octahedral ternary chelates.
Yoshinori Ihara, Shinji Kurose, Takashi Koyama

Solvent Effects on Ion-Pair Distribution and Dimerization of Tetraalkylammonium Salts

Summary
The distribution of tetraalkylammonium ions (C n H2n+1)+N+(R +,TAAn +,n=4−7) with picrate ion (pic ) and inorganic anions X (Cl, Br, Cl0 4), into various inert organic solvents was studied at 25.0°C. The distribution data were analyzed by taking into consideration the distribution of ion pairs, R + X, and the dimerization of the ion pairs, (R + X)2, in the organic phase. The ion-pair, distribution constant, K dist, increases with increasing chain length of the tetraalkylammonium ion and with increasing ionic radius of the anion. The values of K dist show a good correlation with the E T value of solvent, i.e. the solvation ability with respect to the anion, and smoothly increase with increasing E T. The effect of the solvent on the dimerization constants, K dim, is markedly different between the ion pairs of picrate ion and inorganic anions. In the case of picrate, K dim significantly decreases with decreasing length of the alkyl chain of the tetraalkylammonium ion, but hardly changes by changing the solvent. On the other hand, in the case of ion pairs of inorganic anions the value of K dim decreases with decreasing E T and is almost constant for all anions. These results were reasonably explained by the difference of the solvation of the anion moieties of the monomeric and dimeric ion pairs.
Kiyoshi Sawada, Eiji Takahashi, Tomokazu Horie, Keiichi Satoh

Backmatter

Weitere Informationen