Study of intermolecular interactions in aqueous solutions by millimeter spectroscopy

The absorption of millimeter electromagnetic radiation (v=1.4, 1.71, and 5 cm⁻¹) by aqueous solutions of glycine (pH 6.1–6.2) in the concentration range of 0.5–2.5 mol L⁻¹ was measured. It was found that the absorbing ability of the water present in the solutions, is higher than that of pure water. This phenomenon is explained by the presence of a center of negative hydration in the structure of the glycine zwitterion, which results in an increase in the rotational mobility of water molecules immobilized in the hydrate shell of the glycine zwitterion. For Part 5, see Ref. 1. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1305–1307, July, 1997.     

Thermodynamic characteristics of and intermolecular interactions in aqueous solutions of N-methylformamide

The thermodynamic characteristics of aqueous solutions of N-methylformamide were calculated over the whole range of mixture compositions. Intermolecular interaction parameters were determined, and the boundaries of concentration regions with different types of intercomponent association and solution structural organization were established.     

Structural thermodynamic characteristics and intermolecular interactions in aqueous solutions of hexamethylphosphorotriamide

Structural thermodynamic parameters of aqueous solutions of hexamethylphosphorotriamide are calculated. They are discussed together with previously obtained data on aqueous solutions of disubstituted amides of carboxylic acids. The specific and non-specific components of the total energy of intermolecular interactions are determined. The boundaries of concentration regions with different structural organizations of solutions are found, and the preferential solvation parameters of solution components are estimated.     

Thermodynamic characteristics and intermolecular interactions in aqueous solutions of oxyethylated glycols

The thermodynamic characteristics of aqueous solutions of mono-, di-, tri-, and tetraethylene glycols were calculated in the entire range of compositions of the mixtures for various temperatures. The specific and nonspecific terms of the total energy of intermolecular interaction were determined within the framework of a model approach using the internal pressure as a measure of nonspecific interactions in a liquid. The concentration ranges with different types of intercomponent association and of structural organization of solutions depend on the temperature and number of ether groups in the glycol molecules.     

Structral and thermodynamic characteristics and intermolecular interactions in aqueous solutions of diols

The structural and thermodynamic characteristics of aqueous solutions of ethanediol, 1,2-and 1,3-propanediols, and 1,2-and 1,4-butanediols were calculated over the whole range of the compositions of the mixtures. The specific and nonspecific components of the total energy of intermolecular interactions were determined. The boundaries of the concentration regions with different structural organizations of solutions were established, and the parameters of preferable solvation of the solution components were evaluated.     

Structural thermodynamic parameters and intermolecular interactions in aqueous solutions of secondary amides

Structural thermodynamic parameters are calculated for aqueous solutions of secondary amides of carboxylic acids. Specific and nonspecific contributions to the total energy of intermolecular interactions are determined and the boundaries of concentration regions for a various structural organization of solutions are found.     

Structural and thermodynamic properties and intermolecular interactions in aqueous and acetonitrile solutions of aprotic amides

The structural and thermodynamic properties are calculated for mixtures of aprotic amides with water and acetonitrile. The simulation approach is used to identify the specific and nonspecific components of the total energy of intermolecular interactions, which are used to calculate the corresponding contributions to the enthalpy of mixing. The negative enthalpies of mixing in the aqueous mixtures are found to be caused not by heterocomponent specific interactions, but by nonspecific ones. The difference in the structural and thermodynamic properties of the aqueous and nonaqueous mixtures of aprotic amides is shown to be largely due to the behavior of the hydrogen bond network of water and the packing of the resulting solutions.     

Specific features of emulsification of epoxy resins in aqueous solutions of nonionic surfactants

The conditions of emulsification of imported analogs of Russian epoxy resins in the presence of nonionic surfactants were studied. The curing kinetics and the hardness of coatings formed from compounds containing epoxy emulsions and EPILINK 701 and Waterpoxy 751 curing agents were examined.     

Millimeter spectroscopic study of intermolecular interactions in solutions

The absorption of 5 cm^–1 electromagnetic radiation by aqueous solutions of methyl, ethyl, n-, and isopropyl, sec-, iso-, and tert-butyl, and tert-amyl alcohols and ethylene glycol was measured within their solubility limits in water at 20°C. It was found that the observed nonadditivity of absorption (absorption deficit) is a qualitative measure of hydration of alcohols of two types: hydrophilic and hydrophobic. The possibility of distinguishing these effects by millimeter spectroscopy was demonstrated. Hydrophobic hydration makes the basic contribution to the hydration number of aliphatic alcohols. On the example of solutions of ethanol and tert-butanol, it was shown that hydrophobic hydration decreases with an increase in the temperature of the solution due to intensification of hydrophobic interactions between the hydrocarbon radicals.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1755–1761, August, 1989.     

Specific intermolecular interactions in a heterogeneous system benzophenone-titanium dioxide

IR spectroscopy methods (experiment, theoretical simulation) have been applied to study the structural features and intermolecular interactions in a two-component heterogeneous nano-size system benzophenone-titanium dioxide (BPh-TiO₂). IR spectra of the sample were recorded at room temperature within the range 400–4000 cm^?1. The spectra display hydrogen bonding determining the intermolecular interactions between titanium dioxide, BPh molecules, and water in the near-surface layers of nanocrystalline TiO₂ particles. IR spectra of free BPh molecules, water, model H-complexes of BPh with water, and the fragment of hydrated titania surface (BPh…HOH and BPh…Ti≡) have been simulated. Experimental and theoretical spectra were analyzed in the region of stretching vibrations of carbonyl, hydroxyl, and other groups sensitive to a variation of intermolecular interactions. It is found that hydrogen bonding in the near-surface layers of nanocrystalline TiO₂ particles in the two-component heterogeneous nanosystem BPh-TiO₂ gives rise to the formation of complexes BPh-O-Ti(OH)-O-, BPh…HOH, along with complexes of-O-Ti(OH)-O-with water and pure water complexes.     

Specific features of the diffusion of potassium dichromate aqueous solutions in porous glass membranes

The diffusion coefficients of 0.1 M aqueous solution of potassium dichromate (pH 2–8) in a series of glass membranes with the prevailing pore radii from 4.5 to 70 nm were determined. Characteristic features of variation of the diffusion coefficient were correlated with the calculated content of chromium(VI) anionic species over a wide interval of pH of the solution.     

Specific features of the bulk etching of single-crystal semiconducting silicon in aqueous KOH solutions

Bulk chemical etching of single-crystal semiconducting silicon in aqueous alkaline solutions of KOH was studied at various solution temperatures, alkaline component concentrations, and microscopic amounts of a potassium ferricyanide additive. Specific effects of these factors on the process of silicon etching are explained by comparing the corresponding activation energies. The possibility of using alkaline aqueous solutions of KOH with a potassium ferricyanide additive for fabrication of elements in microsystem technology devices is assessed.     

Kinetics of hydrogen bonds in aqueous solutions of cyclodextrin and its methyl-substituted forms

Molecular dynamics simulations of β-cyclodextrin (BCD) and its two methyl-substituted derivatives, namely, heptakis(2,6-di-O-methyl)-β-cyclodextrin (DIMEB) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB) have been performed in aqueous solutions. Detailed analyses were carried out to investigate the effects of substitution on the kinetics of cyclodextrin-water and water-water hydrogen bonds formed by water present in the hydration layers around these macromolecules as well as those formed by water inside their cavities. It is observed that increased geometrical constraints due to substitution of the OH groups of the glucose rings of the BCD molecule result in rapid establishment of hydrogen bond breaking and reformation equilibria for DIMEB and TRIMEB. This has been found to be the microscopic origin of highly rigid arrangement of water around TRIMEB and inside its cavity, as against water in and around BCD and DIMEB.     

Investigation of intermolecular interactions in solutions by means of millimeter-wave spectroscopy 4. Negative and positive hydration in aqueous solutions of urea

Measurements have been made of the absorption of EHF radiation ( 5 cm^–1) by aqueous solutions of urea at 20–70°C, over the entire interval of urea solubility. Excess absorption has been found in comparison with the additive magnitude, and this has been attributed to an increase in the fraction of water molecules in the solution with rotational degrees of freedom. A model has been proposed for the hydration of urea, based on the concept of inhomogeneity of the hydrate shell of urea: stabilization of the structure of water under the influence of carbonyl oxygen and H_cis atoms (positive hydration) and a simultaneous breakdown of the structure of water in the region of two H_trans atoms that have approached to a distance of 2.14 » (negative hydration).For Previous Communication, See [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 314–320, February, 1990.     

Polyelectrolyte solutions: Counterion condensation and intermolecular interactions

This article demonstrates that the neglect of nonlinear effects in the conventional counterion condensation theory for the double layer about a charged cylinder can be significant, especially for phenomena involving intramolecular or intermolecular interactions in dilute solutions. For concentrated solutions the Manning theory derives from a linearized superposition approximation for the potential, in contrast to the cylindrical-cell model, which explicitly treats interactions within an ordered array of parallel cylinders. A new theory which treats interactions explicitly while permitting disorder in two dimensions is presented, and predictions for the osmotic pressure are compared with those from the Manning and cylindrical-cell models.     

Specific features of the absorption of divalent manganese ions from aqueous solutions by zeolites

Sorption properties of natural zeolites from various Russia’s deposits for the Mn²⁺ ion were studied in comparison with various industrial adsorbents and some minerals. It was demonstrated that the equilibrium sorption capacity of these materials can be raised by their Na⁺-modification. The natural zeolites are advantageous at low Mn²⁺ ion concentrations over synthetic cation exchangers and activated carbons. The sorption capacity of the natural zeolites grows with increasing temperature.     

Structural and thermodynamic parameters and intermolecular interactions in aqueous dialkylacetamides

The structural and thermodynamic parameters of aqueous dimethylacetamide and diethylacetamide have been calculated; the specific and nonspecific components of the total energy of intermolecular interactions have been determined. As alkyl radicals increase in size, the concentration regions with different structural organizations of solutions undergo transformation.     

Investigation of intermolecular interactions in solutions by means of millimeter-wave spectroscopy 5. Positive and negative hydration effects in aqueous solutions of methylureas

A study has been made of the concentration dependence of absorption of radiation at 5 cm^–1 by aqueous solutions of urea and its N-methyl, N,N-dimethyl, N,N'-dimethyl, and tetramethyl derivatives; and their effective hydration numbers have been calculated. The low values obtained for the effective hydration numbers of urea, N-methylurea, and N,N'-dimethylurea are explained by the close mutual approach of the two hydrogen atoms in the trans position relative to the carbonyl group (negative hydration); in the case of the N,N-dimethyl and tetramethyl derivatives, no negative hydration effect is observed. For the tetramethylurea, very definite hydrophobic hydration is observed. On the basis of data obtained on the effective hydration number, an estimate has been made of the relative contents of different conformers of methylurea and N,N'-dimethylurea in solution.For Previous Communication, See [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 321–326, February, 1990.     

Intermolecular interactions in aqueous solutions of mebicar

Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1178–1179, June, 1995.