Volumetric Properties of Binary Mixtures of Isomeric Butanols and C8 Solvents at 298.15 K

Excess molar volumes, V _m ^E, over the whole composition range for binary mixtures of 1-butanol, 2-butanol, and 2-methyl-2-propanol + 1-octanol, or 2-octanol, or di-n-butyl ether, or n-hexylacetate were determined at 298.15 K from density measurements carried out with a vibrating-tube densimeter. Small V _m ^E values, both positive and negative, are displayed by mixtures containing 1- or 2-octanol, whereas positive and larger values are always found for mixtures containing dibutyl ether and hexylacetate. These results can be justified in terms of H-bonding interactions and/or steric hindrance due to the branched alkyl chains. Partial molar volumes at infinite dilution of the isomeric butanols in the C8 compounds were also calculated from the apparent molar volumes in dilute solution. The solute-solvent interactions and the effects of the local organisation of the solvent around the butanol molecules were discussed using the void and cavity volumes as different estimates of the intrinsic volume of the molecules. The volumetric behavior of butanols seems to be determined by the solute-solvent interactions rather than packaging effects.     

Ternäre Thallium-Indium-Sulfide: Eine Zusammenfassung

Ternary Thallium Indium Sulfides: A Summary Combined thermal and X-Ray analyses in the ternary system Thallium—Indium—Sulfur show, that the two binary sections Tl₂S? In₂S₃ and TlS? InS contain ternary compounds with unique crystal structures. The chemical formulas of these ternary solids are TlIn₅S₈, TlIn₃S₅, TlInS₂ and Tl₃InS₃ for the section Tl₂S? In₂S₃ and TlIn₅S₆ as well as Tl₃In₅S₈ (metastable high temperature phase) for the section TlS? InS respectively. With TlIn₅S₇ an additional ternary solid could be detected, which is located outside the two sections. It is derived from the binary mixed valence compound In₆S₇ by complete substitution of In⁺ by Tl⁺. The following ionic formulations make the mixed valence character of the ternary Thallium—Indium-Sulfides reasonable: TlIn₅S₈ = Tl⁺(In³⁺)₅(S^2?)₈, TlIn₃S₅ = Tl⁺ (In³⁺)₃(S^2?)₅, TlInS₂ = Tl⁺In³⁺(S^2?)₂, Tl₃InS₃ = (Tl⁺)₃In³⁺ · (S^2?)₃, TlIn₅S₆ = Tl⁺([In₂]⁴⁺)₂In³⁺ (S^2?)₆, Tl₃In₅S₈ = 4 × [(Tl⁺)_0,75 · (In⁺)_0,25In³⁺(S^2?)₂], TlIn₅S₇ = Tl⁺[In₂]⁴⁺ (In³⁺)₃(S^2?)₇. All compounds contain Tl⁺-ions in a characteristic “lone pair coordination” of S^2? ions. Indium atoms however occur with the oxidation numbers +2 (formal, In₂ dumb bells with covalent In? In bonding) and +3 (with In³⁺ in tetrahedral and octahedral coordination of S^2?). Chemical preparation, crystal chemistry and general properties of the ternary solids are discussed, summarized and compared to each other.     

(A19N7)[In4]2 (A = Ca,Sr) and (Ca4N)[In2]: Synthesis,Crystal Structures,Physical Properties,and Chemical Bonding

Single phase powders of (A₁₉N₇)[In₄]₂ (A = Ca, Sr) and (Ca₄N)[In₂] were prepared by reaction of melt beads of the metallic components with nitrogen. The crystal structure of (Ca₁₉N₇)[In₄]₂ was refined based on neutron and X‐ray powder diffraction data. The crystal structure of (Sr₁₉N₇)[In₄]₂ was solved from the X‐ray powder pattern. The structure refinements in combination with results from chemical analyses ascertain the compositions. The compounds (A₁₉N₇)[In₄]₂ (A = Ca, Sr) are isotypes of (Ca₁₉N₇)[Ag₄]₂; (Ca₁₉N₇)[In₄]₂ is probably identical to the earlier reported (Ca_18.5N₇)[In₄]₂. The crystal structure of the isotypes (A₁₉N₇)[In₄]₂ (A = Ca, Sr; cubic, , Ca: a = 1471.65(3) pm; Sr: a = 1561.0(1) pm) contains isolated [In₄] tetrahedra embedded in a framework of edge‐ and vertex‐sharing (A₆N) octahedra. Six of these octahedra are condensed by edge‐sharing around one central A²⁺ ion to form “superoctahedra” (A₁₉N₆) which are connected three‐dimensionally via further octahedra by corner‐sharing. The crystal structure of (Ca₄N)[In₂] (tetragonal, I4₁/amd, a = 491.14(4) pm, c = 2907.7(3) pm) consists of alternating layers of perovskite type slabs of vertex‐sharing octahedra (Ca₂Ca_4/2N) and parallel arranged infinite zigzag chains equation/tex2gif-stack-1.gif[In₂]. In the sense of Zintl‐type counting the compounds (A²⁺)₁₉(N^3?)₇[(In^2.125?)₄]₂ present an electron excess, (Ca²⁺)₄(N^3?)[(In^2.5?)₂] is electron deficient. Metallic properties are supported by electrical resistivity and magnetic susceptibility measurements. The analysis of the electronic structures gives evidence for the existence of homoatomic interactions In–In and significant heteroatomic metal–metal interactions Ca–In which favor the deviations of the title compounds from the (8 – N) rule.     

Solvatochromism in Binary Solvent Mixtures by Means of a Penta‐tert‐butyl Pyridinium N‐Phenolate Betaine Dye

The solvatochromic behavior of a penta‐tert‐butyl prydinium N‐phenolate betaine dye was studied using UV‐visible spectrophotometry in several binary mixture solvents. The solvent polarity parameter, E_T (1) (kcal. mol^?1) was calculated from the position of the longest‐wavelength intramolecular charge transfer absorption band of this penta‐tert‐butyl betaine dye. For binary solvent mixtures, all plots of E_T (1) versus the mole fraction of a more polar component are nonlinear owing to preferential solvation of the probe by one component of the binary solvent mixture. In the computation of E_T (1) it was assumed that the two solvents mixed interact to form a common structure with an E_T (1) value not always intermediate between those of the two solvents mixed. The results obtained are explained by the strong synergism observed for some of the binary mixtures with strong hydrogen bond donors (HBD) solvents such as alcohols.     

Selective solvation of Ag(I) iodate in methanol-dimethyl sulphoxide mixtures

The selective solvation of silver(I) iodate was studied in methanoldimethyl sulohoxide mixtures at 30° C by solubility and EMF measurements. The solubility of the salt increases continuously with the addition of dimethyl sulphoxide after a slight decrease into X_DMSO =0.1. The Gibbs energy of transfer of silver cation (determined on the basis of ferrocene reference method) decreases continuously while that of the iodate ion increases with the addition of dimethyl sulphoxide. The solvent transport number passes through a maximum (Δ = 2.0) around X_DMSO = 0.5. These results were interpreted as arising due to a heteroselective solvation of the salt, the silver ions being preferentially solvated by dimethyl sulphoxide and the iodate ion by methanol in these mixtures.     

Multilayer adsorption with variable thickness at solid-liquid interfaces

 The multilayer adsorption on the solid/liquid interface in binary mixtures was studied by adsorption space filling with constant and variable layer thickness. Adsorption from benzene/n-heptane mixtures was examined on hydrophilic and hydro-phobic surfaces. The free enthalpy of adsorption, Δ₂₁ G=f (x ₁), was calculated from the adsorption excess isotherm by integration of the Gibbs equation. Supposing that the free enthalpy is mainly due to adsorption in the first layer, the composition of this layer can be calculated from the Δ₂₁ G=f (x ₁) function. It was established that the adsorption layer thickness in benzene/heptane mixtures increases significantly with increasing benzene content. This statement was supported by X-ray diffraction on hydrophobic clay minerals. Received: 2 April 1997 Accepted: 10 June 1997     

Ternary β-Cyclodextrin Complexes as Models of Allosteric Effects

Two guests reacting with cyclodextrins (CDs) may form ternary complexes, in addition to the common competition of 1:1 complexes. One of the guests can really be included into the cavity of the CD, while the second guest molecule is either inserted close to the first one or attached to the outer surface of the supramolecule by H-bonding. There is a further possibility when the included guest bears a substituent outside the cavity and the second guest can interact with it. The properties of the ternary species formed are highly influenced by the solely (or primarily) included guest. The changes are attributed to the altered properties of the hydrophilic domain of the CD. The phenomena can be proved by NMR data obtained for some binary systems of -CD inclusion complexes and acetic acid and by the stability constants of the ternary complexes formed. Allosteric effects as well as coenzyme/apoenzyme/substrate interactions could be well modelled by these types of CD complexes.     

Conductometric study of Bu4NClO4 in propylene carbonate-acetonitrile and propylene carbonate-toluene mixtures at 25°C

Conductometric measurements of tetrabutylammonium perchlorate in propylene carbonate-acetonitrile and propylene carbonate-toluene mixtures at 25°C are reported. Limiting molar conductances, association constants and distance of closest approach of ions are calculated. The experimental data were analyzed by means of the Lee-Wheaton equation. The Gilkerson's solvent-solute interaction energy term was calculated from a plot of association constant logarithmvs. reciprocal dielectric constant.     

Conductivity studies on some alkali metal iodides in aqueous N,N-dimethylformamide solutions at 298.15K

Summary Conductance measurements for NaI, KI, RbI, and CsI in water/N,N-dimethylformamide mixtures over the whole composition range at 298.15K are reported. The data were analyzed employing theFuoss-Justice equation in terms of limiting molar conductances (_o),Walden products (_o), and association constants (K _A). The results indicate that the salts are weakly associated in the above solvent mixture. Variation in theWalden products with solvent composition are briefly discussed. The results were also compared with values reported previously for some alkali metal chlorides and bromides.

---

Untersuchungen zur elektrischen Leitfähigkeit einiger Alkalimetalliodide in wäßrigen N,N-Dimethylformamidlösungen bei 298.15K

Zusammenfassung Die elektrische Leitfähigkeite von NaI, KI, RbI und CsI wurde in N,N-Dimethylformamid-Wasser-Mischungen verschiedener Zusammensetzung bei 298.15K gemessen. Die erhaltenen Daten wurden analysiert und bezüglich der Grenzäquivalenzleitfähigkeiten (_o), derWalden-Produkte (_o) und der Assoziationskonstanten (K _A) ausgewertet. Die Ergebnisse zeigen, daß diese Salze in den verwendeten Lösungsmittelgemischen nur schwach assoziiert sind. Die Änderungen derWalden-Produkte in Abhängigkeit der Lösungsmittelzusammensetzung werden kurz diskutiert. Abschließend werden die Resultate mit Ergebnissen früherer Messungen, in denen das Verhalten von Alkalimetallchloriden und Alkalimetallbromiden untersucht wurde, verglichen.

     

Kinetics and equilibrium of multicomponent adsorption on chiraly templated surfaces

In this contribution we propose a simple model of adsorption of a binary (racemic) mixture on a chiraly templated surface. As an example, the adsorption of a liquid mixture of enantiomers on a chiral stationary phase (CSP) is considered. In particular, we study the effect of the lateral interactions in the adsorbed phase on the kinetic and equilibrium isotherms of the enantiomers. Additionally, we investigate the influence of the composition of the surface on the performance of the CSP in the presence of the lateral interactions. To that end, the adsorption of the mixture is modeled by using Monte Carlo simulations as well as by applying an analytical approach involving rate equations coupled with the Mean Field Approximation (MFA). The predictions of the theory are found to be in good agreement with the results of the simulations.