A spectroscopic investigation of the structure of alcohol-water solutions

The v₂ + v₃ combination band of water has been recorded for nine alcohol-water solutions in which the volume fraction of water is less than 2% and for three alcohol-water solutions over the entire range of composition. In dilute solutions it was found that the fraction of symmetrically bonded water was, in general, smaller than in aprotic solvent-water systems. The fraction of nonbonded water protons was greater in alcohols of higher molecular weight and was also greater in tertiary alcohols than in primary ones. The 2v_OH overtone band was recorded for three alcohols in alcohol-rich solutions. Water appears to break up the polymeric alcohol structure, and there appears to be a slight preference for water-water bonds over water-alcohol bonding. Raman spectra of the alcohol C–O stretching mode indicate that water-alcohol bonding is stronger than alcohol-alcohol bonding. The fraction of free alcohol and water OH groups appears to be smaller in solutions of intermediate composition than in the pure liquids. This increased structure of the solutions is consistent with the maxima occurring in the viscosity of alcohol-water solutions.     

Raman and infrared spectroscopic investigation of contact ion pair formation in aqueous cadmium sulfate solutions

Raman and IR data for aqueous CdSO₄ and (NH₄)₂SO₄ solutions have been recorded over broad concentration and temperature ranges. Whereas the v₁-SO ₄ ^2– band profile is symmetrical in (NH₄)₂SO₄ solutions, in CdSO₄ solutions a shoulder appears on the high frequency side which increases in intensity with increasing concentration and temperature. The molar scattering coefficient of the v₁-SO ₄ ^2– band is the same for all forms of sulfate in (NH₄)₂SO₄ and CdSO₄ solutions and is independent of temperature up to 99°C. The high frequency shoulder is attributed to the formation of a contact ion pair [Cd²⁺OSO ₃ ^2– ] (11 associate). Also the v₃-SO ₄ ^2– antisymmetric stretching mode shows a splitting in the CdSO₄ solution. Further spectroscopic evidence for contact ion pair formation is provided by IR spectroscopy. No higher associates or anionic complexes are required to interpret the spectroscopic data. The degree of association has been measured as a function of concentration and temperature. The thermodynamic association constant, K_A=0.15±0.05 kg-mol^–1 at 25°C is estimated from the Raman data by an extrapolation procedure by taking account of the activity coefficients. Values are reported for the activity coefficient of the ion pair. From the Raman temperature dependence studies, the enthalpy of formation for the contact ion pair is estimated to be 10±1 kJ-mol^–1.     

A spectroscopic investigation of the phenolcarboxylic acids ofCynara scolymus

Summary Tigogenin and gitogenin have been isolated from the leaves and flowers, and digitogenin (0.283%) and tigogenin (0.062%) from the seeds ofD. ciliata Trautv. The presence of gitogenin in the seeds has also been established by paper chromatography.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 5, pp. 315–318, 1965     

A spectroscopic study of atmospherically relevant concentrated aqueous nitrate solutions

Concentrated aqueous nitrate aerosols are present in the Earth's atmosphere as a result of heterogeneous reactions of sea salt and mineral dust aerosol with nitrogen oxides (e.g., NO2, NO3, HNO3 and N2O5). Because the water content of these aerosols depends on relative humidity (RH), the composition and nitrate ion concentration will also depend on RH. Unlike the original aerosols, aqueous nitrate aerosols are photochemically active at solar wavelengths. To gain a better understanding of the nitrate ion chromophore in concentrated aqueous nitrate aerosols, we have measured the ATR-FTIR and UV/vis spectra of concentrated nitrate solutions over a large concentration range. Both ATR-FTIR and UV/vis spectroscopy show changes in the nitrate ion spectra with increasing concentration. Ab initio calculations are used to aid in the assignment and interpretation of these spectra. From these data, we predict that the photoreactivity of aqueous nitrate aerosols will strongly depend on relative humidity as the molecular and electronic structure of the nitrate ion becomes increasingly perturbed from that of the isolated ion in highly concentrated atmospherically relevant solutions.     

Zirconium tetrachloride-formaldehyde sigma-complexes: A computational and spectroscopic investigation

We have carried out a combined theoretical-experimental study of the structures and energies of ZrCl(4)-aldehyde complexes using (13)C NMR spectroscopy and a DFT (B3LYP) computational approach. The computational investigation has demonstrated the existence of different types of complexes: a 1:1 complex (H(2)CO-ZrCl(4)), various 2:1 complexes ((H(2)CO)(2)-ZrCl(4)), and several dimeric species. The analysis of the energies involved in the formation of the various complexes has indicated that the dimeric species should correspond to the only adduct observed in the (13)C NMR spectra (carbonyl resonance at 226.96 ppm) when a 1:1 ZrCl(4)/aldehyde molar ratio is used, while the 2:1 complex should be responsible for the signal at 224.30 ppm that is recorded when this molar ratio is 1:2.     

Near-infrared spectroscopic method for the sensitive and direct determination of aggregations of surfactants in various media

A new cmc determination method based on a NIR spectroscopic technique has been developed. Comparing to other cmc determination methods, this NIR method is universal, sensitive, nonintrusive and nonadditive; namely, it can be used for the direct measurements of cmc of normal micelles as well as reversed micelles, without adding any dye or fluorescent probe. cmc values of various surfactants including CTAB, SDS, Triton X-100, Brij-35, Brij-700, Tween-20, SB-12, SB3-10 determined by this method agree very well with those determined by other methods. Additionally, the method can be used for the sensitive and direct determination of cmc values of various nonionic surfactants in room-temperature ionic liquids including [BMIm](+)[PF(6)](-) and [EMIm](+)[Tf(2)N](-). The preliminary results presented here clearly demonstrate that it is possible to use the NIR technique not only to characterize aggregation of surfactants in RTILs but also to determine kinetics and to identify products of reactions in RTILs as well as in microreactors provided by micelles in the RTILs.     

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.     

Raman spectroscopic investigation of silver electrodes

Raman spectroscopy has been applied to the study of the reduction of carbon dioxide and of formate and carbonate ions at a silver electrode. Raman spectra of adsorbed intermediate species, which are as yet only partially identified, have been detected and show marked variations with electrode potential. These spectral variations are clearly correlated with the voltammetric features for carbonate solutions and suggest that these reduction products complicate most measurements on silver electrodes in the cathodic region. The interpretation of the previously reported spectra due to adsorbed pyridine at silver electrodes has been reconsidered; interactions with surface carboxy species may be significant.     

Raman spectroscopic investigation of film thickness

The determination of film thickness is of prime importance in the quality assurance of coated pharmaceutical preparations. The rapid measurement of this parameter is problematic for multi-particulate pellet systems. The aim of this study was to apply the Raman spectroscopic method for the determination of the thickness of polymer coating on pellets. The change of Raman intensity was compared with measured film thickness, which was calculated from the change of the geometric parameters of the pellets, measured with an image-analyzing system. The results revealed that despite some difficulties Raman spectroscopy is a suitable method for the fast and accurate determination of film thickness on multi-particulate systems.     

Raman spectroscopic investigation of carbon nanowalls

Two-dimensional carbon nanowalls (CNWs) were prepared by microwave plasma-enhanced chemical-vapor deposition and scanning electron microscopy was used to observe their morphologies. The Raman observations of different sample orientations and polarizations show that CNWs are well crystallized. Micro-Raman scattering measurements were also carried out with different excitation laser lines (325, 488, 514, 532, and 633 nm). The D band shows a very strong shift of 46.19 cm(-1)eV with excitation laser energy and this has been explained by the double resonance effect. The decreasing intensity ratios IDIG and ID'/IG with increasing laser excitation energy were detected and discussed.     

THz spectroscopic investigation of 2,4-dinitrotoluene

We have investigated the terahertz (THz) spectrum of 2,4-DNT by using Fourier transform infrared spectroscopy in the 0.2–19.5 THz region. We also examined low-frequency intermolecular or phonon modes between 0.2 and 1.8 THz via THz time-domain spectroscopy. The extracted absorption coefficient and refractive index of an intermolecular band at 1.08 THz are 110 cm⁻¹ and 1.67, respectively. Density functional theory (DFT) was applied to obtain structure and vibrational frequencies of 2,4-DNT. The calculated results are in agreement with the experimental data. Observed vibrational frequencies have been interpreted using DFT. Two intermolecular or phonon modes were identified at 1.08 and 2.52 THz.     

Photoelectron spectroscopic investigation of perimidine derivatives

The Hel UPS spectra of acetamidine, perimidine, and four 2-substituted perimidine derivatives have been recorded and interpreted using ab initio and MNDO quantum-chemical calculations. A large interaction between the naphthalene and amidine fragment was concluded from the lowest ionization energy. The color-determining band of these compounds is strongly affected by the intramolecular charge-transfer transitions, which are of low energy because of the low ionization energy of the perimidine moiety.     

Polypropylene photo-stabilization by hindered secondary amines. A spectroscopic investigation

The conversion products from a commercially important photo-stabilizer based on 2,2,6,6-tetramethylpiperidine have been identified and quantified during the photo-oxidation of polypropylene. From a comparison with model compounds and model systems, direct evidence for the dominant involvement of grafted substituted hydroxylamine species was obtained by infra-red spectroscopy. Non-stabilizing conversion products, including N-acyloxy compounds, were also identified and the overall mechanism of photo-protection by hindered amine stabilizers is discussed.     

A spectroscopic investigation of the behavior of anthraquinone in sulfuric acid and oleum

Dissolution of anthraquinone in concentrated sulfuric acid and in oleum is accompanied by a coloration of the solution. It has been observed [1] that in 92–96% sulfuric acid anthraquinone gives a yellow solution, while in 20% oleum the color is red. The assumption has been made [2] that in the first case one of the carbonyl groups of the anthraquinone reacts with the acid, while in the second case both undergo reaction.     

A spectroscopic investigation into the reaction of sodium tetrathionate with cysteine

A spectroscopic investigation into the reaction of sodium tetrathionate with cysteine at pH 5 both at the boil and at room temperature has been carried out. The Raman and infrared spectra of the model compounds cysteine, cysteine-S-sulfonate, cysteine-S-thiosulfonate, sodium thiosulfate and sodium sulfite were also obtained and vibrations involving the sulfur atoms were analyzed in detail. These results were utilized in the interpretation of the spectra obtained from tetrathionate-cysteine reaction mixtures. The reaction supernatants were analyzed by high performance thin layer chromatography while the precipitates were analyzed gravimetrically. It was found that during the reaction, the thiol groups of cysteine are oxidised to give predominantly cysteine-S-sulfonate. Cystine was also detected but was determined gravimetrically to be a minor reaction product. No significant amounts of cysteine-S-thiosulfonate were detected. The reaction is accompanied by the formation of elemental sulfur and a small amount of sulfite. Major reaction pathways are put forth that are consistent with the experimental data.     

A spectroscopic investigation of the phenolcarboxylic acids ofCynara scolymus

Summary Spectroscopic investigations in the UV region of the phenolcarboxylic acids that we have isolated from the leaves ofCynara scolymus have been carried out. It has been found that:1. Free caffeic acid can be distinguished from its esters by the changes in the UV spectra under the influence of sodium ethoxide and sodium acetate.2. An o-dihydroxy grouping in esters can be detected from the bathochromic shift observed with boric acid in the presence of sodium acetate.3. An o-dihydroxy grouping can be detected both in esters and in the free acid under the influence of aluminum chloride.Khimiya Prirodynkh Soedinenii, Vol. 2, No. 5, pp. 303–306, 1966