Aqueous solutions of azoniaspiroalkane halides. VI. Apparent molal volumes and apparent molal heat capacities of chlorides and iodides

Densities and heat capacities of aqueous solutions of azoniaspiroalkane halides, (CH₂) _n N⁺ (CH₂) _n X^– (where X=Cl, I andn=5,6), have been measured at 25°C using a flow densimeter and a flow microcalorimeter. The limiting apparent molal volumes (ø _v ) and apparent molal heat capacities (ø _cp ) obtained from these data are compared with those of the azoniaspiroalkane bromides and the corresponding tetraalkylammonium halides. The concentration dependence of ø _v and ø_cp are examined for clues on the influence of solute hydration, structure, and conformational flexibility on the excess functions of quaternary ammonium halides.     

Investigation of hydration of α-amino acids by means of absorption millimeter spectroscopy

The hydration indexes for 19 protein -amino acids are measured by means of absorption millimeter spectroscopy (AMS) at 31.42 GHz. The plot of the hydration indexes on the area of surface of aliphatic amino acid molecules accessible for water is a straight line located above the points corresponding to aromatic or polar amino acids. The contribution of nonpolar groups in the hydration index is greater than that of polar groups provided that their accessible surface areas are equal. The contribution to hydration of -OH and-CONH₂ groups in Ser. Gin, and Asn coincides in sign with that of pure hydrophobic hydration but the value of the contribution is significantly smaller. The change in mobility of water molecules, which is the basis of the AMS method, may serve as the physicochemical foundation for the construction of a new hydrophobicity scale for amino acids comparable with the already existing scales.Deceased September 2, 1995.Translated fromIzvestiya Akodemii Nauk. Seriya Khimicheskaya, No. 3, pp. 618–622, March, 1996.     

水合二(对叔丁基苄基)二氯化锡的合成及晶体结构

The organotin hydration di(p-tert-butylbenzyl)tin dichloride has been synthesized. The crystal structure of complex has been determined by X-ray diffraction. The crystal belongs to orthorhombic space group Pmma with a=1.108 4(2) nm, b=3.492 0(7) nm, c=0.626 36(12) nm, V=2.424 3(8) nm³, Z=4, D_c=1.376 g·cm^-3, μ(Mo Kα)=12.82 cm^-1, F(000)=1 024, R₁=0.085 9, wR=0.225 7. The bond lengths of Sn-Cl are 0.236 0(2) nm and 0.250 8(4) nm, the Sn-C is 0.212 1(11) nm, the Sn-O is 0.233 2(12) nm. The tin rendered five-coordinate in a distorted trigonal bipyramidal configuration. CCDC: 648618.     

Enthalpies of solution,partial molal heat capacities and apparent molal volumes of sugars and polyols in water

Integral enthalpies of solution of some sugars and polyols in water at low concentrations have been determined calorimetrically at 25 and 35°C. These data have been used to derive heat capacities of solution C°_p at 30°C. Partial molal heat capacities C°_p,2 have been obtained by combining C°_p with C _p,2 ^* , the heat capacity of pure solid compounds. Apparent molal volumes have been obtained from density data. The sugars as well as polyols show significantly high positive C°_p and C°_p,2 values. The results have been explained in terms of a specific hydration model. The effect of substitution of-OH by glycosidic-OCH₃ and of-CHOH by deoxy-CH₂ are also discussed.     

Quantum chemical studies on molecular structural conformations and hydrated forms of salicylamide and O‐hydroxybenzoyl cyanide

Ab initio and density functional theory (DFT) methods have been employed to study the molecular structural conformations and hydrated forms of both salicylamide (SAM) and O‐hydroxybenzoyl cyanide (OHBC). Molecular geometries and energetics have been obtained in the gaseous phase by employing the Møller–Plesset type 2 MP2/6‐311G(2d,2p) and B3LYP/6‐311G(2d,2p) levels of theory. The presence of an electron‐releasing group (SAM) leads to an increase in the energy of the molecular system, while the presence of an electron‐withdrawing group (OHBC) drastically decreases the energy. Chemical reactivity parameters (η and μ) have been calculated using the energy values of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) obtained at the Hartree–Fock (HF)/6‐311G(2d,2p) level of theory for all the conformers and the principle of maximum hardness (MHP) has been tested. The condensed Fukui functions have been calculated using the atomic charges obtained through the natural bond orbital (NBO) analysis scheme for all the optimized structures at the B3LYP/6‐311G(2d,2p) level of theory, and the most reactive sites of the molecules have been identified. Nuclear magnetic resonance (NMR) studies have been carried out at the B3LYP/6‐311G(2d,2p) level of theory for all the conformers in the gaseous phase on the basis of the method of Cheeseman and coworkers. The calculated chemical shift values have been used to discuss the delocalization activity of the electron clouds. The dimeric structures of the most stable conformers of both SAM and OHBC in the gaseous phase have been optimized at the B3LYP/6‐311G(2d,2p) level of theory, and the interaction energies have been calculated. The most stable conformers of both compounds bear an intramolecular hydrogen bond, which gives rise to the formation of a pseudo‐aromatic ring. These conformers have been allowed to interact with the water molecule. Special emphasis has been given to analysis of the intermolecular hydrogen bonds of the hydrated conformers. Self‐consistent reaction field (SCRF) theory has been employed to optimize all the conformers in the aqueous phase (ε = 78.39) at the B3LYP/6‐311G(2d,2p) level of theory, and the solvent effect has been studied. Vibrational frequency analysis has been performed for all the optimized structures at MP2/6‐311G(2d,2p) level of theory, and the stationary points corresponding to local minima without imaginary frequencies have been obtained for all the molecular structures. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Quantitative chemical composition of thin films with infrared spectroscopic ellipsometry: application to hydrated oxide films on aluminium

A method to quantify the composition of thin films using infrared spectroscopic ellipsometry (IRSE), supplemented by visible spectroscopic ellipsometry (VISSE), is proposed. Because ellipsometry measures the thickness and optical constants of a surface layer simultaneously, the absorption coefficient of the film as a function of wavelength can be obtained. Using values of the absorption coefficients for the pure components of the film, the percentages (mol.% or wt.%) of each component in the film can be calculated. The method is demonstrated in a study of the hydration of oxide films on electropolished aluminium and the anodically formed barrier oxide film. The IRSE technique shows that hydration of the films by immersion in boiling water results in the conversion of aluminium oxide to pseudoboehmite. Copyright © 2003 John Wiley & Sons, Ltd.     

Hydration of calixarene-containing polymers

The hydration of cross-linked polymers containing tetramethylcalix[4]resorcinarene and tetraphenylcalix[4]resorcinarene was studied using the isopiestic, calorimetric, and MNDO/PM3 method. Adsorption of water vapor by calixarene-containing polymers leads to type II isotherms according to the Brunauer—Deming—Deming—Teller classification. In the framework of the Aranovich model of polymolecular adsorption, the monolayer capacity and pure heat of adsorption were calculated. The first monolayer is formed from 3—4 water molecules adsorbed due to hydrogen bonding with OH groups of calixarenes. The integral thermodynamic functions of hydration of the calixarene-containing polymers in water at 298 K were determined.     

Enthalpy of mixing of hydrated melts. II. Evidence for an endothermic step in the chlorocomplex formation of zinc

The enthalpies of mixing measured for the systems x(ZnCl₂+RH₂O)-(1–x)(LiCl+RH₂O) are reported. In contrast to the exothermic effects for R=4, the mixing processes at R=6 are considerably endothermic. For R=5, the sign of H _M depends on the composition. The mixing enthalpies of these hydrated melts are controlled by an endothermic step in the chlorocomplex formation of zinc and the exothermic hydration of lithium cations.     

Dielectric spectroscopy on aqueous solutions of pyridine and its derivatives

The complex (dielectric) permittivity has been measured as a function of frequency between 1 MHz and 40 GHz for aqueous solutions of pyridine, 2- and 3-methylpyridine, as well as 2,4- and 2,6-dimethylpyridine at various temperatures and solute concentrations. Different relaxation spectral functions are used to analytically represent the data, in particular the Cole-Cole function. The solute contribution to the extrapolated static permittivity has been calculated to show that, in correspondence with other aqueous solutions of organic molecules and ions, the permittivity of the solvent seems to be enhanced with respect to the pure water value. Also in accordance with other aqueous systems it is found that the principal dielectric relaxation time for equimolar solutions of stereo isomers at the same temperature may significantly differ from one another. A further result is the finding of an unusually strong temperature dependence in the relaxation time of the 1 molar solution of 2,6-dimethylpyridine.     

Hydration of Cement Slurry in The Presence of Spent Cracking Catalyst

The physicochemical properties of spent fluidized bed cracking catalyst and its influence on hydration process of cement slurry were studied. The samples were cement slurries prepared with water/solid=0.5 and additions of used catalyst amounted to 0, 5, 10, 15, 20 and 25%with resp. to the solid. After definite time they were subjected to thermogravimetric analysis (TG, DTG, DTA) and, in order to determine the progress of reaction with water, the heat of hydration was measured by means of isotherm calorimetry. The studies disclosed that the spent cracking catalyst is not merely an inactive filler in cement slurries, but it modifies the course of the hydration process. The spent catalyst is a pozzolana additive and its presence leads to a decrease of calcium hydroxide contents in the system. The spent catalyst affect on the heat of cement hydration. Small amounts additive accelerate the process of binding. This revised version was published online in August 2006 with corrections to the Cover Date.