Vibrational spectra of 1:2 ordered perovskites

The infrared and Raman spectra of some perovskites with general formula A₃BB′₂O₉ are reported, viz. Sr₃MgNb₂O₉, Sr₃CaNb₂O₉, Pb₃MgNb₂O₉, and Ba₃Gd₂WO₉. The interpretation is by far not as simple as for 1:1 ordered perovskites. Only a rough assignment of the internal modes of the niobate and tungstate octahedra can be made. The spectra of the niobates are very sensitive to the degree of order between the divalent metal ions and the Nb⁵⁺ ions among the smaller cation sublattice. This is evaluated qualitatively.     

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 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 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.     

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 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 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 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 and quantum mechanical assignments for 1-nitropropene

The i.r. spectra of cis and trans 1-nitropropene have been recorded in the vapor phase and in various solvents. Theoretical calculations at the Hartree—Fock level with a 3-21G(d) basis set were carried out yielding vibrational frequencies for nitromethane and cis and trans 1-nitropropene. Assignment of fundamentals was assisted by solvent effects on 1-nitropropene. Evidence is obtained for inter-molecular hydrogen bonding.     

Vibrational spectra of fluorine-containing azoxybenzenes

Conclusions The vibrations of the azoxy group in azoxybenzene have been assigned on the basis of calculations of the frequencies and normal modes of vibrations for it. The introduction of fluorine atoms into the benzene rings has practically no influence on the frequencies of the stretching vibrations of the azoxy group. An increase in the number of fluorine atoms in the benzene rings of azoxybenzenes lowers the intensities of the stretching vibrations of the azoxy and phenyl groups in the IR spectra.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1537–1544, July, 1986.     

Vibrational spectra of trinitromethane derivatives

Spectroscopic parameters of trinitromethane derivatives RC(NO₂)₃ (R = F, Cl, Br, I, NC, NF₂, N₃) were determined. Vibrational frequencies and modes were calculated and the assignment of experimental spectra was performed. Spectral features due to the mutual influence of the C(NO₂)₃ group and other atomic groups and particular atoms were revealed.