IR study of aqueous metal perchlorate solutions

Aqueous solutions of Mn(II), Co(II), Ni(II), and Zn(II) perchlorates, and for comparison, Mg(II) and Ca(II) perchlorates, have been studied by IR spectroscopy using HDO as an indicator. The investigations were carried out over the entire available concentration range of these salts. Computer deconvolution of the measured spectra demonstrates the effect of metal cations on the HDO molecules.     

Global non-ideality effects in adsorption of organic substances from dilute aqueous solutions on activated carbon

Summary A method for the quantitative estimation of the global non-ideality of the adsorption of weak organic electrolytes on activated carbon from dilute aqueous solutions is presented. The method is based on the analysis of aGraham plot which reflects the adsorption isotherm deviations from ideality. Averaging these deviations over the whole range of adsorption, one gets a single value representing the global non-ideality of a system. The method also allows to estimate the contributions of heterogeneity and interactions in the adsorbed phase to the global non-ideality effect. The theoretical considerations are illustrated by some model calculations. The usefulness of the method is tested for experimental data of benzoic and salicyclic acid adsorption over a wide range ofpH and concentrations.

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Globaler Effekt der Nicht-Idealität bei der Adsorption organischer Substanzen aus verdünnten wässerigen Lösungen an Aktivkohle

Zusammenfassung Es wird eine Methode zur quantitativen Abschätzung der globalen Nicht-Idealität für die Adsorption schwacher organischer Elektrolyte aus verdünnten wässerigen Lösungen an Aktivkohle vorgestellt. Diese Methode basiert auf der Analyse der bekanntenGraham-Abhängigkeit, die die Abweichung der Adsorptionsisotherme von der Idealität zeigt. Bei Errechnung des Durchschnittwertes dieser Abweichung über den ganzen Asorptionsbereich erhält man einen Wert, der die globale Nicht-Idealität für ein Adsorptionssystem charakterisiert. Die Methode erlaubt auch, den Beitrag der Heterogenität und der Wechselwirkungen in der Adsorptionsphase zum globalen Effekt der Nicht-Idealität abzuschätzen. Die theoretischen Erörterungen werden an Hand von Modellberechnungen illustriert. Die Nutzbarkeit der Methode wurde mit experimentellen Daten der Benzoe- und Salicylsäureadsorption in einem weiten Bereich vonpH und Konzentration getestet.

     

IR spectroscopic studies on the transmission of substituent effects to carbonyl and thiocarbonyl stretching frequencies in 4-substituted phenyl-4,5-dihydrobenzo [f] [1,4] oxazepin-3 (2H)-ones (thiones)

Single and dual substituent correlation analysis were applied to study transmission of substituent effects on IR carbonyl and thiocarbonyl stretching frequencies of 4-substituted phenyl-4,5-dihydrobenzo [f] [1,4] oxazepin-3 (2H)-ones (5a–n) and -thiones (6a–n). The substituent effects were estimated on the basis of results of the statistical analysis. The differences among the regression coefficients were discussed in terms of the relative importance of the substituent field and resonance effects. For a better understanding of the results, density functional theory (DFT) calculations were performed to determine the preferred geometry and to calculate the theoretical carbonyl and thiocarbonyl stretching frequencies.     

Interpretation of IR spectra of epoxysaccharides based on the theoretical calculation of frequencies and intensities of normal vibrations

A detailed assignment of absorption bands in IR spectra of methyl 3,4-anhydro-α-D-talo-hexapyranoside and methyl 2,3-anhydro-4-deoxy-α-D-ribo-hexapyranoside is first made based on the complete calculation of frequencies and absolute intensities of normal vibrations of molecules and their comparison with the corresponding experimental values. The effect of the epoxy group on the bands characteristic of the pyranose ring is analyzed. The charactericity of spectral features of oxymethyl substitution for the hydroxyl group and the oxirane ring is studied.     

IR spectroscopic study of the adsorption of MeOH and H2O on decationized zeolites

The IR spectra of decationized zeolites with adsorbed bases have been analyzed. A correlation between the shift (OH) of the center of gravity of the set of bandsA,B, andC (components of the (OH) vibration) and the strength of the H-bond between the bridging hydroxyl groups and the molecule of a base has been found. This is evidence in support of the Fermi-resonance nature of the perturbations of the (OH) vibration. Spectral data on the adsorption of H₂O and MeOH on decationized zcolitcs that cannot be interpreted in terms of the formation of complexes with strong H-bonds have been obtained. Arguments in favor of the formation of H₃O⁺ and MeOH₂ ⁺ ions linked to the neighboring oxygen atoms in the zeolitc latticevia two identical hydrogen bridges have been presented.Na—Y zeolites were synthesized by N. N. FeoktistovaTranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1377–1381, June, 1996.     

Inversion of ν(MHal) stretching frequencies in the spectra of dihalosilylenes, -germylenes, -stannylenes,and their complexes with Lewis bases

The vibrational spectra of tetravalent metal halides (M = Si, Ge, Sn) and the corresponding dihalocarbene analogs M^IIHal₂, obtained by the authors, and the relevant published data are compared. The spectra of the M^IIHal₂ species exhibit inversion of the M-Hal stretching frequencies (ν^s(M^IIHal) > ν ^as(M^IIHal)). This can be used for analytical purposes and allows one to distinguish between the spectra of the M^IV and M^II halides. The IR and Raman spectra of the complexes of dihalogermylenes and -stannylenes with triphenylphosphine and 1,4-dioxane also exhibit inversion of the ν(MHal) stretching frequencies. This confirms the conclusion drawn earlier based on the analysis of the geometric parameters and reactivities of the complexes in question that the divalent state of the M atom in these species is retained. Dedicated to Academician N. K. Kochetkov on the occasion of his 90th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1089–1092, May, 2005.     

IR spectroscopic study of ion-molecular interactions in the methanesulfonic acid—N,N-dimethylformamide system

Complex formation in the methanesulfonic acid (MSA)-DMF system was studied by Multiple Attenuated Total Reflectance (MATR) IR spectroscopy at 30°C within the composition range from neat MSA up to neat DMF. Depending on the ratio of components, two types of complexes with a strong quasi-symmetrical H bond (1 and2) are formed. The uncharged complex1 is a quasi-ion pair with the (O…H…O) bridge. Complex2 is formed by a protonated DMF molecule and the (A…H…A)⁻ anion bound as an ion pair. It is established that complexes1 are solvated by DMF molecules in an excess of a base. Solvation or2 in an excess of an acid corresponds to a change from contact to contact-separated ion pairs. Continuous absorption spectra of charged and uncharged complexes1 and2 were obtained. The schemes of acid-base interactions in the MSA-DMF and HCl-DMF systems were compared. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2484–2489, December, 1998.     

Viscometric and conductometric study of polyelectrolytes of low charge density in salt free aqueous solutions

Viscometric and conductometric measurements have been performed on dilute, salt free solutions of poly(vinyl alcohol) (PVA) and poly(vinyl alcohol, vinyl sulphate ester) copolymer salts in order to get information on transition from a neutral to charged macromolecules. With increasing linear charge density from a very low value to a moderate one a non linear dependence of polyelectrolyte effect on copolymer composition was observed. A comparison has shown that there is a close analogy between the expansion of polyanions and swelling of polyelectrolyte networks at comparable linear charge density range. Due to the intra- and inter-molecular mobile ionic bridges a considerable contraction was pointed out by viscometry for barium, magnesium and copper salts. However, the differences in properties of counterions of higher charge number indicates that in addition to the valency, there is a definite chemical effect, too. It has been revealed by the electric conductance measurements that the transition from a neutral to charged macromolecules could be a very complex one calling for a new and more detailed theoretical consideration of polyelectrolyte solutions.     

Influence of molecular electronic properties on the IR spectra of dimeric hydrogen bond systems: polarized spectra of 2-hydroxybenzothiazole and 2-mercaptobenzothiazole crystals

We have studied the polarized IR spectra of the hydrogen-bonded molecular crystals of 2-hydroxybenzothiazole (HBT) and 2-mercaptobenzothiazole (MBT). The crystal structure of 2-hydroxybenzothiazole was determined by X-ray diffraction. The polarized spectra of the crystals were measured, in the frequency ranges of the ν_N-H and ν_N-D bands, at room temperature, and at 77 K. In both systems an extremely strong H/D isotopic effect in the spectra was observed, involving reduction of the well-developed ν_N-H band fine structure to a single prominent ν_N-D line only. The two ν_N-H bands were also shown to exhibit almost identical properties, band shapes, temperature and dichroic properties included. The spectra were quantitatively reconstituted, along with the strong isotopic effect, when calculated using the ‘strong-coupling’ theory, assuming the centrosymmetric dimers of HBT or MBT to be the structural units responsible for the crystalline spectral properties. The similarity of the spectra of the two crystalline systems was considered to be a result of longer-distance couplings between the proton vibrations in the dimers, via the aromatic ring electrons. When investigating the ‘residual’ ν_N-H band shapes for crystals isotopically diluted by deuterium, we observed some ‘self-organization’ effects in the spectra, indicating the energetically favored presence of two identical hydrogen isotopes in each hydrogen bond dimer.     

Effects of added nonionic surfactant and inorganic salt on the rheology of sugar surfactant and CTAB aqueous solutions

The effect of adding tri(oxyethylene) dodecyl ether (C₁₂EO₃) on the phase and rheological behavior of sucrose hexadecanoate and CTAB aqueous solutions in the presence of added salt (NaBr) was investigated. Viscoelastic solutions are formed in CTAB and C₁₆SE systems upon addition of lipophilic nonionic surfactant C₁₂EO₃. The zero-shear viscosity shows a maximum at a certain mixing fraction of C₁₂EO₃, except in the case of the aqueous CTAB/C₁₂EO₃ system in the absence of salt. The rheological properties are strongly affected by the addition of salt to the CTAB systems but they remain unaltered in the case of C₁₆SE systems. In ionic systems, the mixing fraction of C₁₂EO₃ for the maximum viscosity depends on salt concentration.     

Effects of dynamical couplings in hydrogen bond systems in the polarized IR spectra of 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde crystals

This paper presents the investigation results of the polarized IR spectra of 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde crystals measured at 293 and 77 K. Analysis of the results concerned the linear dichroic, H/D isotopic and temperature effects observed in the spectra of the hydrogen and deuterium bond at the frequency ranges of the ν_O–H and the ν_O–D bands, respectively. The main spectral properties of the crystals were interpreted in terms of the “strong-coupling” theory on the basis of the hydrogen bond dimer model. The spectra revealed that the strongest vibrational exciton coupling involved the closely-spaced hydrogen bonds, each belonging to a different chain of associated molecules. The reason for two different crystalline systems, are characterized by almost identical ν_O–H and ν_O–D band shapes, is explained. It was proved that a random distribution of the protons and deuterons took place in the lattices of the isotopically diluted crystals.     

Effect of the electrolyte concentration on cation binding in aqueous surfactant solutions.

Electrospray ionisation mass spectrometry (ESI-MS) is used for the qualitative and quantitative study of ion binding to interfaces. The ESI-MS measurements are carried out in aqueous solutions of sodium dodecyl sulphate (SDS) in the presence of NaCl, NH(4)ClO(4) , KCl, or Mg(ClO(4))(2) . The effect of the electrolyte concentration on the fractions, y(cation(+) ), of the DS(-) monomers bound to the cations is shown. Moreover, the binding stability of different cations with DS(-) monomers is determined versus the electrolyte concentration. This stability and the y(Na(+) ) values (the Na(+) ions derived from SDS), estimated in the presence of a given electrolyte, are quantitatively correlated with the electrolyte cation effect on the water structure. We also present calibration curves from which the molar concentrations of the sodium ions (derived from SDS) and of the other cations (derived from the electrolyte), bound to the SDS-micelle surface at a given electrolyte concentration, can be obtained. Besides, specific ion effects (Hofmeister effects) are considered for 1:1 electrolytes.     

Polarized IR spectra of the hydrogen bond in acetic acid crystals

The paper presents the results of our investigations of the polarized IR spectra of the hydrogen bond in crystals of acetic acid, CH₃COOH, as well as in crystals of three deuterium isotopomers of the compound: CH₃COOD, CD₃COOH and CD₃COOD. The spectra were measured at 283 K and at 77 K by a transmission method using polarized light. Theoretical analysis of the results concerned the linear dichroic effects, together with the H/D isotopic and temperature effects observed in the solid-state IR spectra of the hydrogen and of the deuterium bond at the frequency ranges of the ν_O–H and the ν_O–D bands, respectively. Basic spectral properties of the crystals can be interpreted satisfactorily in terms of one of the quantitative theories of the IR spectra of the hydrogen bond, i.e. the “strong-coupling” theory or the “relaxation” theory when a hydrogen bond dimer model is used. From the spectra obtained it resulted that the strongest exciton coupling involved the closely spaced hydrogen bonds, belonging to different chains of associated acetic acid molecules. These results contradict the former explanation of the spectra within a model, which assumed a strong vibrational exciton coupling between four hydrogen bonds in a unit cell. On analyzing the spectra of isotopically diluted crystalline samples of acetic acid it has been proved that a non-random distribution of the protons and deuterons takes place in the hydrogen bond lattices. This non-conventional isotopic effect is a result of dynamical co-operative interactions involving hydrogen bonds in the system. Simultaneously it has been also found that in an individual hydrogen bonded chain in the crystals, distribution of the hydrogen isotope atoms H and D was fully random. The H/D isotopic “self-organization” mechanism most probably involves a pair of hydrogen bonds from each unit cell where each hydrogen bond belongs to a different chain.     

Effects of strong inter-hydrogen bond dynamical couplings in the polarized IR spectra of adipic acid crystals

This paper presents the results of the re-investigation of polarized IR spectra of adipic acid and of its d₂, d₈ and d₁₀ deuterium derivative crystals. The spectra were measured at 77 K by a transmission method using polarized light for two different crystalline faces. Theoretical analysis concerned linear dichroic effects and H/D isotopic effects observed in the spectra of the hydrogen and deuterium bonds in adipic acid crystals at the frequency ranges of the ν_O–H and the ν_O–D bands. The two-branch fine structure pattern of the ν_O–H and ν_O–D bands and the basic linear dichroic effects characterizing them were ascribed to the vibronic mechanism of vibrational dipole selection rule breaking for IR transitions in centrosymmetric hydrogen bond dimers. It was proved that for isotopically diluted crystalline samples of adipic acid, a non-random distribution of protons and deuterons occurs in the dimers (H/D isotopic “self-organization” effect). This effect results from the dynamical co-operative interactions involving the dimeric hydrogen bonds.     

关于苯及其衍生物在盐水溶液中的活度系数的研究

摘录了25℃时苯,甲苯,邻位、间位、对位二甲苯,间位、对位二氯苯及萘在NaF,LiCL,NaBr,NEt~4Br等25种盐的水溶液中的活度系数f,它们的lgf-c~s的关系符合Setchenow盐效应公式。计算了苯及其衍生物在上述25种盐水溶液中的各种盐效应理论的k~s,主要有:1)Debye-macAulay静电理论;2)Conway-Desnoyers-Smith静电理论;3)Masterton-Lee定标粒子理论;4)McDevit-Long内压力理论;5)改进的内压力理论;6)改进的Bockris色散力理论。对各种理论值比较后可以看到改进后的内压力理论k~s值与实验k~s值较为吻合。Bockris色散力理论经改进后计算比较简单,可以判断盐效应符号,盐效应顺序也基本正确。     

NMR chemical shifts of xenon in aqueous solutions of amphiphiles: A new probe of the hydrophobic environment

The chemical shift of elemental xenon in solution is sensitive to the environment. The shift arises from van der Waals interactions in most liquids, but an additional effect is present in aqueous media yielding a larger shift than expected. In water the shift is affected by the presence of low molecular weight amphiphiles, and its variation with composition can reveal the presence of hydrophobic hydration of the amphiphile. The results are similar to the conclusions drawn from other physical studies. Data are presented for aqueous solutions of methanol, ethanol, n-propanol, iso-propanol, tert-butanol, dimethylsulfoxide, p-dioxane, and acetonitrile.     

A comparative study on the monovalent and divalent cation separation of polymeric films and membranes from salt solutions under diffusion-dialysis

This study deals with selective separation of mono- and divalent cations from aqueous salt solutions using polymeric films based on polyethylene (PE) and polyamide6 (PA6), and two different commercial nanofiltration (NF) membranes. The diffusion rates (D) of ions (Na⁺ and Ca²⁺), separation factors (α) and ion rejections (R) of the films and NF membranes are examined comparatively as well as their surface morphology and hydrophilicity. It is observed that the diffusion rates of Na⁺ are in the range of 0.7–1.8 × 10⁻⁸cm² .s⁻¹ in the decreasing order of PE > NF90 > NF270 > PA6 while Ca²⁺ shows diffusion rates of 7.4–18.4 × 10⁻⁸ cm² .s⁻¹ in the increasing order of NF270 > NF90 ≈ PA6 > PE. Rejection values of the polymeric films and NF membranes against to Na⁺ and Ca²⁺ vary between 90% and 99.6%.The highest α(Ca²⁺/Na⁺) is found to be 20 for PA6 film. D, α, and R value of both polymeric films and NF membranes are strongly affected by the existence of osmosis during diffusion-dialysis and the sizes of hydrated sodiu and calcium ions. In conclusion, the film based on PA6 may be a good alternative for selective separation of mono- an divalent cations.     

Thermochemical study of the influence of tetraalkylammonium cation sizes on the interaction of their salts with formamide and carbamide in aqueous solutions

Solutions of tetrahexylammonium salts in mixtures of water with additives of hydrophilic substances formamide and carbamide were studied by the thermochemical method at 298.15 K. The enthalpies of solution of tetrahexylammonium perchlorate were measured by the sedimentation method, and the enthalpies of solution of tetrahexylammonium bromide were calculated. The enthalpic coefficients of pair interaction electrolyte—amide in an aqueous solution were determined. The data obtained were compared with those for te tramethyl- tetraethyl- and tetrabutylammonium salts to study the influence of the tetraalkylammonium cation size on its solvation and interaction with amides in an aqueous solution.