Composition of heteroassociates formed in a binary liquid system HF-Et<Subscript>2</Subscript>O

IR spectra and densities of solutions in a binary liquid system (BLS) HF-Et₂O were measured for the first time for the molar ratios of the components ranging from 1: 12 to 14: 1 and 31: 1, respectively. An analysis of the concentration dependences of the normalized (to the total number of moles of the BLS components in 1 L) absorbance and excess density of the studied solutions revealed that they contained heteroassociates with stoichiometric ratios of the molecules of 1: 2, 2: 1, 4: 1, and 11–12: 1. The concentration range in which each associate is formed in the binary mixture HF-Et₂O was estimated for all the associates. The results obtained were compared with the data on the HF: Solv ratios (Solv is solvent) in molecular complexes that prevail in the seven BLS HF-organic solvent studied earlier. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1833–1839, September, 2008.     

Composition and structure of heteroassociates formed in the HF-<Emphasis Type="Italic">N,N</Emphasis>-dimethylformamide binary liquid system

The concentration dependence of the normalized (to the total number of moles of the components per liter) absorbance of HF solutions in DMF in ratios from 1: 12 to 7: 1 was analyzed. In the binary liquid system (BLS) under consideration, there are molecular complexes with stoichiometric ratios of 1: 1 and ≥10: 1 along with heteroassociates (HA) with the HF to DMF ratio of 4: 1, which have been found earlier. For each HA, the concentration range, in which HA is formed in BLS, was estimated, and the positions of the stretching bands of HF were determined. The optimal configurations and the vibrational frequencies of the molecular complexes (HF) _m ·(DMF) _n (m = 1, 2, 4, 8; n = 1, 2) with different topologies were calculated using the density functional theory (B3LYP/6-31++G(d,p)). The relative stability and structural features of the latter complexes were investigated. The complex formation in the HF-DMF system was analyzed. The structures of HA with stoichiometric ratios of 1: 1 and 4: 1 were determined by comparing the results of calculations and experimental data.     

IR spectra of hydrogen fluoride solutions in n-propanol

The densities of solutions of HF in n-PrOH were measured at different mole ratios of the components (from 1 : 12 to 3 : 1), and their IR spectra were recorded. The spectra of all the solutions exhibit absorption bands at 3500, 2600, and 1800 cm^–1 and continuous absorption (CA) in the frequency range from 3500 to 1300 cm^–1. The intensities of these bands and CA increase in proportion to the concentration of HF in solution. The difference between the experimental solution density and the calculated additive sum of the densities of the solution components behaves analogously. The formation of heterocomplexes with a stoichiometric ratio greater than 3 : 1 in the HF solutions in propanol was revealed. These heterocomplexes have large identical structural fragments with the strong quasi-symmetric H-bond. The results of calculations of the stretching vibration frequencies and relative stability of different cyclic pentamers suggest that such a fragment is the most stable cyclic heteropentamer, (HF)₂(nPrOH)₃, in which the HF molecules occupy the neighboring positions.     

Relationship between free molecules and molecules involved in various heteroassociates in HF-Me2CO solution

The experimental and computational methods to acquire the data on the relationship between free molecules and molecules involved in various heteroassociates (HA) in the HF—organic solvent binary liquid system (BLS) were developed and applied to the series of HF solutions in acetone. The first method is appropriate at the component molar ratios from 0 : 1 to 6 : 1 under the condition that the IR spectrum of the solvent molecule contains a band, whose frequency and intensity can be measured as the molecule passes from the free state to the composition of all HA formed in the BLS. The second method is based on the consideration of the balance between free molecules and molecules involved in HA of the solvent and HF. This method requires the knowledge of molar ratios of the components of the solution at which each HA appears in the solution. It is shown that in an HF-Me₂CO solution the main part of the molecules is involved in the HA composition starting from the HF content ～0.25 molar fraction, whereas 90–100% molecules are associated at an HF content of ～0.50–0.93 molar fraction.     

Equilibrium Compositions of HF Solutions in <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylformamide

For HF solutions in DMF, concentration-dependent fractions of DMF molecules (α(DMF)) that remain unassociated and that enter heteroassociates (HAs) of 1 : 1, 4 : 1, and 12 : 1 molecular stoichiometries were obtained by two independent methods, namely, from an analysis of IR spectra and by calculating the material balance. The experimental way was shown to be enough exact in determining the ratio between the solvent molecules in four different states up to ~83 mol % HF. The equilibrium compositions of HF–DMF solutions were estimated over the entire range of concentrations. Starting with [HF] of ~25 mol %, more than one-half HF molecules are associated, and at [HF] of ~50–92 mol %, at least 90% of the HF molecules are associated. The equilibrium composition of HF–organic solvent (Solv) solutions in which HAs of 1 : 1, 1 : 4, and 1 : 12 molecular stoichiometries are formed, can be described by a single set of α(HF–Solv) versus concentration plots.     

Composition and structure of heteroassociates formed in a binary liquid system HF-CH<Subscript>3</Subscript>CN

The concentration dependence of normalized absorbance (to the total number of moles of components in one liter) of HF solutions in acetonitrile (1:12–10:1) is analyzed. It is found that in the binary liquid system (BLS) under study molecular complexes with stoichiometric 1:1 and ～10:1 ratios of molecules occur along with the heteroassociates (HAs) found previously with the ratio HF:CH₃CN of 4:1. For each of the HAs the concentration range at which it is formed in BLS is evaluated, and the positions of HF stretching vibrational bands are found. Optimum configurations and vibrational frequencies of molecular complexes (HF) _m ·(CH₃CN) _n (m = 1–6, n = 1–2) of various topology are calculated using the density functional method (B3LYP/6-31 ++ G (d, p)). Their relative stability and the structure peculiarities are studied; complexation tendencies in the HF-CH₃CN system are revealed. The structure of HAs with 1:1 and 4:1 stoichiometric ratios of molecules is determined by comparing the results of calculations and experiment.     

Composition of heteroassociates formed in an HF-diethyl ketone liquid binary system

The IR spectra and solution densities in a binary liquid system (BLS) HF-diethyl ketone were measured for the first time upon variation of the component molar ratio from 1: 12 to 12: 1 and to 27: 1, respectively. Analysis of the concentration dependences of normalized (to the total number of moles of BLS components in 1 L) optical density and excess density of the solutions revealed the presence of 1: 1, 4: 1, and ∼12: 1 heteroassociates (HAs). For each associate, the concentration range in which it forms in the HF-(C₂H₅)₂CO binary mixture was estimated. It was shown that, at component molar ratios from 2: 1 to 9: 1, all three types of HAs are present simultaneously.     

Structure of heteroassociates formed in the HF-(CH<Subscript>3</Subscript>)<Subscript>2</Subscript>CO binary liquid system

The vibrational spectra of a series of HF solutions in acetone (1:20–8.9:1) are analyzed with the help of special techniques. It is shown that three types of strong heteroassociates (HAs) with 1:1, 4:1, and ≥10:1 stoichiometric ratios of the molecules are formed in the HF-(CH₃)₂CO binary liquid system. The concentration ranges of the existence of HAs in the solution and the stretching vibrational frequency of their constituent HF molecules are estimated. The density functional method (B3LYP/6-31++G(d,p)) is used to calculate the optimal configurations and IR spectra of the (HF) _m ·((CH₃)₂CO) _n molecular complexes (m = 1, 2, 4, 8, n = 1, 2) of different structure. The relative stability of the latter is studied. By comparing the calculated and experimental data, the composition (2:2 and 4:1) and structure of two types of HAs are determined.     

Structure of heteroassociates formed in the HF-(C<Subscript>2</Subscript>H<Subscript>5</Subscript>)<Subscript>2</Subscript>O liquid system

The aim of this work was to determine the structure of stable heteroassociates (HAs) with the stoichiometric ratios 1:2, 2:1, and 4:1 of molecules formed in the HF-(C₂H₅)₂O binary liquid system. The stretching frequencies of HF molecules found for each HA using a special procedure for processing IR spectra were compared with the calculated frequencies V HF of the stable molecular complexes (HF)_m ((C₂H₅)₂O)_n (m = 1, 2, 4, 8; n = 1, 2) with different topologies by the density functional method (B3LYP/6-31++G(d,p)). As a result, it was shown that the most stable (among H-bonded complexes with the same stoichiometric ratio of molecules) HAs HF((C₂H₅)₂O)₂, (HF)₄ ((C₂H₅)₂O)₂, and (HF)₈-((C₂H₅)₂O)₂ formed in HF solutions in diethyl ether. All of them had a cyclic structure and a common peculiarity of structure: only one lone electron pair of the oxygen atom of the (C₂H₅)₂O molecules is involved in hydrogen bonding.     

Excess volumes of the binary mixtures of trichloroethylene withn-alcohols at 30 and 40°C

Volumes of mixing binary systems formed by trichloroethylene with n-alcohols (1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, and 1-octanol) were measured as a function of composition at 30 and 40°C, by dilatometric measurements. All the systems show a change of sign for V ^E from negative to positive as the mole fraction trichloroethylene increases at both temperatures The positive value of the excess volumes increase as carbon chain length increases. The results are explained in terms of depolymerization of hydrogen bonded alcohol aggregates and weak hydrogen-bonding interaction of the type Cl-H–O between unlike molecules.     

Solubility of <Emphasis Type="Italic">d</Emphasis>-elements salts in organic and aqueous-organic solvents: III. Influence of intermolecular association on solubility of cadmium bromide and iodide

Solubility in the systems CdX₂–H₂O–Solv (X = Br, I; Solv = dimethyl sulfoxide, N,N-dimethyl acetamide, N,N-dimethyl formamide, and 1,4-dioxane) at 25°C was measured by the isothermal saturation method. A relation between the shape of the solubility isotherm and the structure of the binary solvent depending on its composition was found. Positions of solubility maxima and isotherms inflection points in the most cases correlate with destruction of intermolecular associates formed by solvent components.     

Thermodynamic study of complex formation between Ni2+ and Co2+ cations and 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (kryptofix 5) in binary mixed nonaqueous solutions

Conductometric titrations were performed in pure and binary solvent solutions of ethyl acetate (EtOAc), methyl acetate (MeOAc) and methanol (MeOH) with acetonitrile (AN) at 288, 298, 308, and 318 K to determine the stoichiometry, the complex stability constants and the standard thermodynamic parameters for the complexation of nickel(II) and cobalt(II) cations with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (kryptofix 5). The stability constants of the resulting 1:1 complexes formed between the metal cations and the ligand in different solvent mixtures were determined by computer fitting of the conductance-mole ratio data. The results revealed that the stability order of (kryptofix 5)-Ni²⁺ and (kryptofix 5)-Co²⁺ complexes changes with nature and composition of the solvent system. There is a non-linear relationship between the logK _f values of complexes and the mole fraction of acetonitrile in the mixed solvent system. In addition, the conductometric data show that the stoichiometry of the complexes formed between the nickel(II) and cobalt(II) cations with the acyclic ligand changes with the nature of the solvent. The enthalpy and entropy values for the 1: 1 [ML] complexation reactions were evaluated from the temperature dependence of the formation constants. Thermodynamically, in most of systems, the complexation processes of nickel(II) and cobalt(II) cations with kryptofix 5, are both enthalpy and entropy stabilized and the values of these parameters are influenced by the nature and composition of the binary mixed solvent solutions.     

Heterocomplexes in liquid mixtures MeOH—HF

The IR spectra and densities of MeOH—HF liquid mixtures were measured for component molar ratios ranging from 12 : 1 to 1 : 3. The IR spectra of all of the solutions exhibit bands with maxima at 3500, 2600, and 1800 cm^–1 and continuous absorption (CA) in the region of 3500—1300 cm^–1. The intensities of these bands and the CA increase with an increase in the HF concentration. A similar behavior was found for the difference between the experimental solution density and the additive sum of the solution component densities. Ab initio SCF calculations of the (MeOH)_5–n (HF) _n cyclic complexes (n = 0—5) were performed using the 6-31G basis set. The observed properties of MeOH—HF liquid mixtures may be due to the formation of heterocomplexes with a stable cyclic fragment consisting of more than four MeOH and HF molecules.     

Solvation of complexes with strong symmetric H bonds in the methanesulfonic acid—2-pyrrolidone system

Multiple Attenuated Total Reflectance (MATR) IR spectra of solutions of methanesulfonic acid (MSA) in 2-pyrrolidone (Pyr) (0—100 % MSA) were examined at 30 °C. Depending on the ratio of components, two types of species with strong symmetric H bonds are formed: uncharged quasi-ion pairs of 1 : 1 composition and anions (AHA)^–. The solvation of quasi-ion pairs by base molecules and of the (AHA)^– anions by acid molecules was detected. The data on the influence of the hydrogen bond donor and acceptor on the IR spectra of the quasi-ion pairs and (AHA)^– anions are presented.     

TiO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> binary xerogels: Synthesis and characterization

Silica/titania binary xerogels were prepared by joint hydrolysis of the ingredients. Gels of various compositions were characterized by ¹H NMR spectroscopy, IR spectroscopy, and thermogravimetry. The spectral characteristics of binary systems differ considerably from mere superposition of the spectra of the two constituent compounds and the spectrum of a mechanical mixture. A feasibility was demonstrated for controlling the acid properties of binary oxide gels via varying the component mole ratio.     

Relationship between variously associated molecules in the HF-Et2CO solution

Data on the relationship between the molecules involved in various heteroassociates (HAs) and “free” molecules in the HF-Et₂CO binary liquid system (BLS) are obtained by two independent methods: experimental and computational. The first method is applicable in the 0:1–6:1 molar range provided that the IR spectrum of the solvent molecule contains a band whose frequency and intensity can be measured when this molecule passes from the “free state” to the composition of all Has present in BLS. The second method is based on taking into account the material balance between the “free” molecules and molecules involved in various HAs of the solvent and HF. This method requires the knowledge of stoichiometric ratios of molecules in HAs and concentrations at which they appear in the solution. It is shown that in HF-Et₂CO BLS, starting from the molar fraction of HF of ～0.25, the majority of molecules is involved in the composition of the complexes, and at the molar fraction of HF of ～0.50–0.92 already 90–100% of molecules of the solution form HAs.     

Isobaric vapor–liquid equilibria for binary systems α-phenylethylamine + toluene and α-phenylethylamine + cyclohexane at 100 kPa

In this paper the results of the vapor–liquid equilibria study at 100 kPa are presented for two binary systems: α-phenylethylamine(1) + toluene (2) and (α-phenylethylamine(1) + cyclohexane(2)). The binary VLE data of the two systems were correlated by the Wilson, NRTL, and UNIQUAC models. For each binary system the deviations between the results of the correlations and the experimental data have been calculated. For the both binary systems the average relative deviations in temperature for the three models were lower than 0.99%. The average absolute deviations in vapour phase composition (mole fractions) and in temperature T were lower than 0.0271 and 1.93 K, respectively. Thermodynamic consistency has been tested for all vapor-liquid equilibrium data by the Herrington method. The values calculated by Wilson and NRTL equations satisfied the thermodynamics consistency test for the both two systems, while the values calculated by UNIQUAC equation didn’t.     

Bubble point measurements of binary mixtures formed by ethyl benzene with selected compounds at 95.35 kPa

Bubble point temperatures (at 95.35 kPa) over the entire composition range were measured for the binary mixtures formed by ethyl benzene with: acetyl acetone, o-, and p-cresols, 1-hexanol, and tetraethoxysilane, employing a Swietoslawski type ebulliometer. Wilson equation was used to represent the measured liquid phase composition versus bubble point temperature data, and the computed values of the vapor phase mole fractions, activity coefficients, and excess Gibbs free energy were tabulated and briefly discussed.     

Bubble point measurements of binary mixtures formed by 1-hexanol with selected nitro-compounds and substituted benzenes at 95.6 kPa

Bubble point measurements (at 95.6 kPa) over the entire composition range are carried out for the binary mixtures formed by 1-hexanol with the: nitro-compounds (acetonitrile, acrylonitrile N,N-dimethyl formamide and aniline) and substituted benzenes (o-xylene, chlorobenzene, and nitrobenzene), employing a Swietoslawski type ebulliometer. Wilson model is found to represent the measured liquid phase composition versus bubble point temperature data well. Computed values of the vapor phase mole fractions and liquid phase activity coefficients are tabulated and briefly discussed.     

Acoustic,excess thermodynamical,molecular interaction and anti-microbial activity studies on binary liquid mixtures of geranyl acetate and benzyl benzoate in the temperature range of 303.15K–318.15K

The binary organic liquid mixture of geranyl acetate + benzyl benzoate was taken at different mole fractions and various temperatures 303.15K, 308.15K, 313.15K and 318.15K and measured their density, ultrasonic sound velocity and viscosity. Data from experiments were used to calculate variations in binary systems at different temperatures regarding excess acoustic parameters. Variations in ultrasonic velocity, intermolecular free length, and adiabatic compressibility were among these. To estimate the coefficients and standard errors for the excess/deviation functions, multi-parametric non-linear regression analysis was used to fit a Redlich-Kister polynomial with the calculated excess/deviation functions. Changes in these properties with temperature and composition have been investigated in the molecular interactions between the molecules of the binary mixtures. FTIR spectra also support the results. Furthermore, liquid mixtures and individual compounds were studied for their antibacterial activity.