Vibrational spectra and the structures of alkali metal caprolactamates

Based on analysis of the IR and Raman spectra of Na and K caprolactamates it has been established that these exist not in two forms (lactamic and lactimic), as previously proposed, but rather in one form, intermediate in structure between these two forms, in which the negative charge is delocalized uniformly across the amide bond. It has also been shown that spectral bands at 1560 and 1400 cm–1 for these salts correspond to the antisymmetric and symmetric stretching vibrations of this bond.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 335–339, February, 1990.     

Vibrational spectra and structure of mixed alkali borotungstate glasses: Evidence of mixed alkali effect

Mixed alkali borotungstate glasses with xLi₂O–(30 − x)Na₂O–10WO₃–60B₂O₃ (0 ≤ x ≤ 30) composition were prepared by melt quench technique. FT-IR and Raman spectroscopic studies were employed to investigate the structure of all the prepared glasses. Acting as complementary techniques, both IR and Raman measurements revealed that the network structure of the present glasses mainly based on BO₃ and BO₄ units placed in different structural groups. Raman spectra confirm the IR results regarding the presence of tungsten ions mainly as WO₆ groups. In the present work, the mixed alkali effect (MAE) has been investigated in the above glass system using FTIR and Raman studies.     

Infrared and Raman spectra of alkali metal salts of TCNQ

The infrared and Raman spectra of the series of alkali metal salts of the monoanion radical of tetracyanoquinodimethane MTCNQ (M = Li, Na and K) are observed and analysed both in the low-frequency lattice vibration region and in the intramolecular vibration region. The vibrational assignments are made, by comparing the spectra of MTCNQ with one another and investigating the difference between the powder and solution spectra and the temperature dependence of the spectra. The monomer—dimer phase transition in NaTCNQ and KTCNQ of the columnar stacking of TCNQ⁻ does not cause a marked change in the low-frequency spectra due to the lattice vibrations. The vibronically activated bands of the totally symmetric modes of the TCNQ⁻ anion are observed in the infrared spectra, which are associated with the charge-transfer intermolecular interaction. A lattice dynamical analysis for the optically active crystal vibrations of NaTCNQ and KTCNQ is performed, and the result of this calculation also verifies the vibrational assignments of the low-frequency infrared and Raman bands attributed experimentally to the translational and rotational lattice modes.     

Vibrational spectra of bridging carbonyl groups in transition metal carbonyl clusters

The spherical harmonic model (SHM), previously used for the analysis of the terminal nu(CO) vibrations of transition metal carbonyl clusters, is applied to the corresponding bridging CO modes. The model is applicable, although the spectra show a greater sensitivity to the molecular geometry than is the case for their terminal counterparts. The reasons for this sensitivity are discussed. When both micro(2) and micro(3) CO groups are present in a molecule, a spectral distinction may not be apparent.     

Vibrational spectra of alkali hydrogen selenites,selenous acid,and their deuterated analogs

The infrared and Raman spectra of alkali hydrogen selenites [(MHSeO₃), where M = Li, Na, K, or Cs], selenous acid (H₂Seo₃), and their deuterated analogs have been recorded and interpreted. The internal mode frequencies observed in sodium hydrogen selenite, selenous acid, and sodium trihydrogen selenite are used to generate general valence force constants for HSeO^?₃ and H₂SeO₃ under the assumption of C_s geometry for each species. Calculations of observed deuterium frequency shifts are made to aid in the assignments of the various internal modes. A low-temperature proton-triggered phase transition is observed in CsHSeO₃ and is confirmed in KHSeO₃. A discussion of the effects of proton order and disorder upon the selenite frequencies is also presented.     

Quantum molecular interpretation of absorption spectra of small alkali metal clusters

The ab initio CI study of excited states of alkali metal clusters accounts for spectroscopical patterns obtained from the photodepletion spectra of the neutral or cationic species, predicts the excitation energies and transition intensities in the complete agreement with the measured quantities and permits an assignment of the cluster structures. The calculated optical spectra for various clusters with 4 and 8 valence electrons are compared: Na₄, Li₄, LiNa₃; Na₈ and Na ₉ ⁺ . A molecular interpretation of the rich spectra of tetramers as well as of the dominant intense transitions located at ～2.5–2.7 eV in the case of Na₈ and Na ₉ ⁺ with the weak fine structure shifted to the red is given.     

Vibrational spectra of hexamethylcyclodisilazane

The synthesis and ring cleavage reactions of 2-alkyl-2-trimethylsilylmethyl-1.3-dithianes are described. The cleavage lead to 2-alkylthio-1-vinylsilanes and, via silicon migration, to 2-[3-alkylthio-3-(trimethylsilyl)propylthio]-1-alkenes.     

Vibrational spectra of mesitylene

Conclusions The Raman spectra of liquid mesitylene and the IR spectra (4000-100 cm^–1) of liquid and gaseous mesitylene were studied. An assignment of the frequencies according to the symmetry and the form of the vibrations is proposed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2265–2270, October, 1982.     

Vibrational spectra of diethylsulfoxide

FT IR and Raman spectroscopic studies of pure diethylsulfoxide (DESO) in the liquid and in the solid states and its solutions in various solvents have been performed. Analysis of SO- and CH-stretching regions in a wide range of concentration shows that the bands may be fitted satisfactorily by considering seven components. In addition, fundamental frequencies have been assigned using ab initio calculations at the RHF/3-21G* levels. The results obtained confirm a viewpoint on a self-associative structure of DESO, and support the hypothesis of the existence of different types of intermolecular associates including both dipole-dipole and hydrogen bonding mechanisms.     

Vibrational spectra of isocyanocyclopropane

Infra-red spectra of isocyanocyclopropane have been measured from 4000 to 400 cm⁻¹ in the vapour and to 200 cm⁻¹ in the liquid phase. The Raman spectrum of the liquid was obtained from 4000 to 50 cm⁻¹. A vibrational assignment of all fundamentals is proposed, which is in accord with those of structurally related molecules. Comparison with the vibrational spectra of cyanocyclopropane and cyclopropylacetylene shows the presence of a sizeable inductive effect of the nitrogen atom in isocyanocyclopropane.     

Vibrational spectra of polyacetylenes

A considerable amount of information about optical and electronic properties of polyacetylenes has been obtained during the last decade from vibrational spectroscopy. In this lecture several basic points not yet fully understood will be discussed and a new method for evaluating the vibrational density of states for random defects will be presented.     

Vibrational spectra of dipropylsulfoxide

FTIR and Raman spectra analysis of pure dipropylsulfoxide (DPSO), binary mixtures of DPSO/CCl(4), and DPSO/water has been first performed. The complex pattern of spectra has been explained on the basis of molecular interactions between DPSO and other molecules and, in the aqueous solutions, the role of both hydrophilic and hydrophobic interactions have been discussed depending on the concentrations. The changes in the intensities and in the frequencies of DPSO bands on concentration have been considered. The curve fitting procedure has been performed for both SO and C-H stretching region, and, on the basis of deconvolution results different type of molecular interactions have been considered. Density function theory DFT/(B3LYP) method has been used to determine the optimized geometry for free DPSO and for 1 DPSO:1 water complex. On the basis of the 6-31+G(d) quality sets parameters, the DFT calculated bond parameters and harmonic vibrations are in a very good agreement with experimental data.     

Vibrational spectra of indole

Polarized i.r. spectra of partially oriented indole crystals grown from the melt between pressed salt plates and the Raman spectra of the melt and polycrystalline indole are reported. Some fundamental vibrational assignments and the manifestations of the NH ⋯ π interaction in the vibrational spectra are discussed.