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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of solution chemistry 1 (1972), S. 1-2 
    ISSN: 1572-8927
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8927
    Keywords: Chemical shifts ; water proton (influence) ; nonelectrolytes ; polar and nonpolar groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydroxyl-proton chemical shifts of alcohol mixtures and aqueous solutions containing some nonelectrolytes (alcohols, ketones, cyclic ethers, and amines) have been measured at 60 MHz and at 0°C. Methyl-proton resonance of the solutes was used as the internal reference and the water-proton shifts in solutions were measured with respect to pure water. Downfield shifts for some alcohols (particularly tertiary butanol and iso-propanol), cyclic ethers, and amines in the water-rich region were confirmed For alcohols and some other nonelectrolytes in water, the observed shifts were decomposed to component contributions arising from the “polar group” effect, “solute proton” effect, and “nonpolar group” effect. Polar effects are found to contribute a substantial fraction of the observed downfield shifts. After subtracting these polar contributions, however, there still remains certain amounts of downfield shifts which may be attributed to the effect of nonpolar groups on the water structure. The downfield shifts are found to be relatively large when the solutes have branched alkyl groups with nearly spherical shape and with diameters of about 5 Å. Strikingly large downfield shifts of water proton resonance were found for some secondary amines and tertiary diamines with globular shape. However, in view of the extrapolation technique employed in evaluating the “polar group” effect, the downfield “nonpolar group” effect we estimated should be considered as the upper limits.
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  • 3
    ISSN: 1572-8927
    Keywords: Calorimetry ; thermodynamics ; complex formation ; copper dipeptides ; zinc dipeptides ; cadmium dipeptides ; dipeptide complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Calorimetric and potentiometric studies have been made at 25°C of the formation of zinc and cadmium complexes of diglycine and of the copper complexes of glycylsarcosine, glycineamide, glycylproline, glycyl-l-alanine, α-alanylglycine, and glycyl-γ-aminobutyric acid. In addition, a potentiometric investigation has been made of the formation of copperl-alanyl-l-alanine complexes. The data have been used to calculate ΔG, ΔH, and ΔS values for all the equilibria involved and, in the case of copper, these data strongly support a common structure for all the mono complexes at lower pH in which the copper is bound to the terminal—NH2 and the oxygen of the peptide group. At higher pH, thermodynamic functions have been determined for the dissociation of the peptide hydrogen atom which is labilized by the copper atom.
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  • 4
    ISSN: 1572-8927
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract NMR studies indicate that the relaxation rate of17O-enriched water is enhanced in monosaccharide solutions, and it is greater in hexose solutions than with a pentose, ribose. Three dielectric relaxations have been isolated and assigned to bulk water〈solute reorientation〈hydration water in order of increasing relaxation time. The extent of hydration evaluated from dielectric and NMR measurements agree. If, for example, we define “hydration number” as the average number of water molecules which are hydrogen-bonded to the monosaccharides such that the lifetime of the bond is longer than that between molecules in pure water, then at 50°C the hydration number of glucose is 2.3, and that of ribose is 1.2. The hydration number of glucose decreases with increasing temperature, and it is suggested that at 80°C both hexoses and the pentose only form stable monohydrates. At lower temperature the hydration depends on the compatibility of the monosaccharide conformation with the “lattice” structural component of water. This model also explains (1) the relaxation mechanisms, (2) the thermodynamic properties of the solutions and, in particular, the similarity between the hydration numbers calculated from relaxation data and from free-energy measurements, (3) why the concentration of tetrahedrally bonded water molecules, as detected by Raman measurements, in sugar solutions is higher than that implied by thermodynamic and relaxation measurements, and (4) the temperature dependence of the conformational equilibria of ribose.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of solution chemistry 1 (1972), S. 197-198 
    ISSN: 1572-8927
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-8927
    Keywords: 2-Oxazolidones ; dielectric constants ; viscosities ; physical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Eight derivatives of 2-oxazolidone, , have been synthesized by the Homeyer method and purified by fractional freezing or fractional distillation to obtain low-conducting liquids. Dielectric constants, viscosities, densities, and refractive indices of these 2-oxazolidones have been determined at several temperatures within the range 25 to 75°C. Values for activation energies of viscous flow also have been calculated. The isomeric 3-methyl and 5-methyl derivatives of 2-oxazolidone have high dielectric constants which differ only slightly from that of water. The 3-substituted (or N-substituted) 2-oxazolidones exhibit the most favorable combination of physical properties, stability, and ease of purification and appear to have excellent potential as new nonaqueous solvents.
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  • 7
    ISSN: 1572-8927
    Keywords: Urea ; apparent volume ; polar solvents ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Apparent molar volumes of urea are measured over a temperature range in water, methanol, ethanol, formamide, DMF and DMSO. The limiting apparent molar volumes show a large variation in different solvents. In marked contrast to the situation in water, the temperature dependence of the limiting apparent molar volumes in the nonaqueous solvents is slight. The concentration dependence is discussed qualitatively in terms of solute association.
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  • 8
    ISSN: 1572-8927
    Keywords: Structural ; cospheres ; models ; thermodynamics ; aqueous ; solutions ; tetraalkylammonium ; halides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The hypernetted-chain integral-equation-approximation method is used to calculate the ion-ion pair correlation functions and the thermodynamic properties of models of the kind previously studied,(1) which are based on an ion-ion pair potential having four terms: the usual Coulomb term, a core repulsion term, a term to represent a well-known dielectric repulsion effect, and a “Gurney” term to represent the effect of the overlap of the structure-modified regions, solvation shells or “cospheres,” when the ions come close together. The coefficientA ij of the last term for each pairi,j of ionic species is the only parameter that is adjusted to fit the solution data. It is determined by fitting excess-free-energy (osmotic-coefficient) data. It is scaled to represent the molar free-energy change of water displaced from the cospheres when they overlap. The corresponding entropy changeS ij and volume changeV ij are determined by fitting, respectively, excessenthalpy and excess-volume data. Problems of finding a uniquely “best” set of parameters are discussed together with many examples of variations of the model, most of which require further investigation. A consistent set of these parameters, which represents much of what is known about the thermodynamic excess functions of these solutions at concentrations up to about 0.5M, is interpreted as far as possible in terms of the data for thermodynamic solvation functions for the same systems.
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  • 9
    ISSN: 1572-8927
    Keywords: Deuterium oxide ; mixed solvents ; water acidity ; isotope effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A potentiometric method using a glass electrode has been applied to determination of ionization constants for deuterium oxide (D2O) in binary mixtures of D2O with dioxane, tetrahydrofuran, acetone, dimethylsulfoxide, CH3CH2OD, and CH3OD at 25°C. The results are compared with values of ionization constants for H2O obtained previously in the corresponding H2O-organic mixtures, and the isotope effect is shown to be small. Further calculations with the D2O results show that the first five solvents mentioned above are neither appreciably acidic nor basic in D2O solution, but that CH3OD shows slightly acidic behavior (pKa=16.0±0.3).
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  • 10
    ISSN: 1572-8927
    Keywords: Effect of pressure ; ionization of water ; molal volume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The apparent molal volumes of dilute (0.002 to 1.0m) aqueous HCl and NaOH solutions have been determined at 0, 25, and 50°C and NaCl solutions at 50°C. The partial molal volumes ( $$\bar V$$ ) of HCl, NaOH, and NaCl solutions have been determined from these apparent molal volumes and other reliable data from the literature. The partial-molal-volume changes ( $$\Delta \bar V_1 $$ ) for the ionization of water, H2O→H++OH−, have been determined from 0 to 50°C and 0 to 1m ionic strength from the partial molal volumes of HCl, NaOH, NaCl, and H2O. The partial molal compressibilities ( $$\bar K$$ for HCl, NaOH, NaCl, and H2O have been estimated from data in the literature and used to determine the partial molal compressibility changes ( $$\Delta \bar K_1 $$ ) for the ionization of water from 0 to 50°C and 0 to 1m ionic strength. The effect of pressure on the ionization constant of water has been estimated from partial-molal-volume and compressibility changes using the relation $$RTln(K^P /K) = - \Delta \bar V(P - 1) + \tfrac{1}{2}\Delta \bar K(P - 1)^2 $$ from 0 to 50°C and 0 to 2000 bars. The results agree very well with the directly measured values.
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