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71.
G. Zundel 《Angewandte Chemie (International ed. in English)》1969,8(7):499-509
In hydration, the intermolecular interaction is of decisive importance, since the ions modify the properties of the hydration water molecules, and the water molecules in turn have a strong influence on the interaction between the ions. These processes can be studied in detail with the aid of IR spectroscopy, which in addition provides a picture of the hydration structure. IR spectroscopy also shows that the excess protons are in energy bands and allows the detection of the proton dispersion forces acting between tunneling protons. The results of IR studies on polyelectrolytes contribute to our understanding of the many biological processes that depend on the behavior of ions. 相似文献
72.
The growth and reduction of compact (α-) and overlying hydrous (β-) oxide films on polycrystalline Au electrodes in aqueous 0.1 M H2SO4 solutions have been investigated using potentiostatic, cyclic voltammetry, ellipsometric and quartz crystal microbalance (QCMB) techniques. All α-oxide films, formed with time at constant potentials up to 2.6 V, or by multicycling of the potential, are non-hydrated in nature, even when covered by a thick β-oxide film. The α-oxide film composition is suggested to be AuO below 1.5 V, and a mixture of AuO+Au2O3 at potentials above this, becoming predominantly Au2O3 at very high potentials. Up to three monolayers of Au2O3 can be formed. When formed at constant potential, the β-oxide film becomes increasingly hydrated as it thickens with time of growth, with a mass to charge ratio and refractive index consistent with Au2O3·H2O and later with Au2O3·2H2O. In contrast, the β-oxide film formed by multicycling has a higher mass overall, and becomes less hydrated as it thickens with time, with a mass and refractive index consistent with Au2O3·10H2O at short times, ranging to Au2O3·2H2O as the film thickens. 相似文献
73.
74.
Amino acid ionic liquids (AAILs) have huge potential in the field of protein chemistry, enzymatic reactions, templates for synthetic study etc. which is due to their distinctive properties like unique acid-base characteristics, tunable hydrophobicity, hydrogen bonding ability and strong hydration effects. To explore the field of bio-ionic liquids for its real life applications and sustainable technology development, it is essential to have better understanding of these newly researched liquid salts in life’s most chosen medium, i.e. in aqueous medium, through study of their physicochemical properties in aqueous solutions. In this context, we are reporting herewith measurements and analysis of volumetric properties in the temperature range of (293.15 to 313.25) K and acoustic properties at 298.15 K in the concentration range of (0.05 to 0.5) mol · kg−1 for aqueous solutions of 1-butyl-3-methylimidazolium [Bmim] based amino acid ionic liquids, prepared from glycine, l-alanine, l-valine, l-leucine and l-isoleucine. The experimental density and sound speed data were used to obtain apparent, partial and limiting molar volumes as well as isentropic and isothermal compressibility properties. These data have been further used to understand electrostriction as well as concentration dependence of internal pressure. The hydration numbers for AAILs in aqueous medium were estimated from compressibility data using Passynski method and the estimated ionic hydration numbers are compared with those obtained using activity data. The results are explained in terms of cooperative hydration effects, hydrophobic interactions, kosmotropic behavior of AAILs, etc. 相似文献
75.
Cristbal Prez Amanda L. Steber Berhane Temelso Zbigniew Kisiel Melanie Schnell 《Angewandte Chemie (International ed. in English)》2020,59(22):8401-8405
Carbohydrates are ubiquitous biomolecules in nature. The vast majority of their biomolecular activity takes place in aqueous environments. Molecular reactivity and functionality are, therefore, often strongly influenced by not only interactions with equivalent counterparts, but also with the surrounding water molecules. Glycoaldehyde (Gly) represents a prototypical system to identify the relevant interactions and the balance that governs them. Here we present a broadband rotational‐spectroscopy study on the stepwise hydration of the Gly dimer with up to three water molecules. We reveal the preferred hydrogen‐bond networks formed when water molecules sequentially bond to the sugar dimer. We observe that the dimer structure and the hydrogen‐bond networks at play remarkably change upon the addition of just a single water molecule to the dimer. Further addition of water molecules does not significantly alter the observed hydrogen‐bond topologies. 相似文献
76.
A periodical interaction model of LDHs-Cl-yH2O has been proposed. The geometry optimization and energy of the layered double hydroxides (LDHs) were calculated using CASTEP/LDA method at the CA-PZ level. The distribution of H2O in the interlayer and the super-molecular interaction between host layer and guest anion have been investigated by analyzing the geometric parameters, charge population, energy, and density of state (DOS). The results showed that there was a strong super-molecular interaction between the host layer and the guest anion Cl−. In the system of LDHs-Cl-yH2O, the interlayer distance increased gradually then tended to invariableness. And in the process of hydration of LDHs-Cl, hydrogen bonding was superior to electrostatic interaction, and layer-water type hydrogen bonding was a little stronger than anion-water type hydrogen bonding between H2O and the rest of the structure. When y was 1 or 2, Cl− and the plane of water were parallel to the layer; while y was 3 or 4, distribution of Cl− and water was random. Moreover, the LDHs-Cl-yH2O would change from ionic crystal to molecular crystal with the increase of number of water molecule. The hydration of LDHs-Cl would achieve a definite saturation state. 相似文献
77.
Yoshimasa Orita Akio Ando Hiroshi Abe Shin-ichi Yamabe Hélène Berthod Alberte Pullman 《Theoretical chemistry accounts》1979,54(1):73-82
SCFab initio computations have been performed on the structure, molecular potential and hydration scheme of thiourea in view of a comparison
with urea and more generally as a model of the conjugated S=CNH-group as compared to O=CNH-. In contrast to the carbonyl oxygen,
both σ and π acceptor, the sulfur atom of the thiocarbonyl is a σ donor but a π acceptor and this results in an enhancement
of the double-bond character of thiourea. The CN bond is less attractive for a proton than urea. The hydration scheme indicates
a maximum number of four water molecules directly bound to thiourea. 相似文献
78.
Ronald Grigg Anuch Hasakunpaisarn Boonsong Kongkathip Alan Pettman 《Tetrahedron》2005,61(39):9356-9367
Palladium catalysed 3-component cascades are described involving aryl/heteroaryl iodides, allene and benzyl malononitrile. Catalytic monohydration and monoamination of malononitriles to the corresponding monoamides and monoamidines are also described together with several examples of mono-oxazoline formation. 相似文献
79.
Yizhak Marcus 《Journal of solution chemistry》2008,37(8):1071-1098
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. 相似文献
80.
The expression for Gibbs energy of electrolyte solutions has been derived taking into account the contribution of interactions
of the hydrated shells of ions. It is in good agreement with data for the dependence of the hydration number on concentration.
The contribution of different interactions to the activity coefficient depending on concentration has been analyzed. The possibility
of determining parameters which characterize the composition of hydrated shells of individual atoms from experimental data
has been considered. 相似文献