The vibrational spectra of cyanoethylenes

The frequencies and forms of the vibrations of acrylonitrile, cis- and trans-dicyanoethylenes, tricyanoethylene, and tetracyanoethylene have been calculated using various sets of force constants which take account of bond interaction. It has been shown that the vibrational spectra of all the cyanoethylenes (like those of cyanoacetylene and cyanogen studied earlier) are described by means of force constants which are extremely similar to those for simple molecules containing the same bonds. The observed values of the force constants characterizing the C=C, C-C, and C=N bonds and their interaction have been compared with the constants in hydrocarbons with analogous structures and in simple molecules. It has been concluded that in cyanoethylenes the intramolecular mutual influence of the multiple bonds leads to very slight delocalization of the electrons, compared with that for conjugated hydrocarbons.     

The vibrational spectra of phthalimide

The polarised i.r. and Raman spectra from three orthogonal faces of single crystalline phthalimide have been measured. Supplemented by information from solution spectra (depolarisation ratios from the Raman spectra), it is possible to assign the fundamental vibrations for the molecule almost completely. The experimental assignments are confirmed by an approximate normal coordinate calculation.     

NMR spectra of the perfluoro-2-methallyl cation

Conclusions This is the first report of the preparation and¹⁹F and¹³C NMR spectral characterization of the perfluoro-2-methallylic cation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2811–2813, December, 1984.     

The vibrational spectra and conformations of ethylbenzene

Infrared spectra (4000-250 cm-1) of the liquid, amorphous, crystalline solids and solutions in liquid krypton and Raman spectra (2500-20 cm-1) of the liquid as well as the amorphous and crystalline solids of ethylbenzene and its deuterated analogue-ethylbenzene-d(10) have been recorded. The spectra indicate that in the liquid and amorphous solids a small amount of a second conformer is present, whereas only one conformer remains in the crystalline phases. Assignments of the observed band wave numbers are discussed by comparison with normal mode wave numbers and IR and RS intensities calculated from ab initio 6-31G force fields and optimised geometries for both conformers for two species. All of the normal modes of conformers have been assigned.     

The vibrational spectra of N-Cl maleimide

The infrared spectra of N-Cl maleimide as a Nujol mull and dissolved in various solvents were recorded between 4000 and 30 cm^?1. Raman spectra of the crystalline solid and saturated solution in CH₃CN were recorded and semiquantitative polarization measurements were made.The fundamental frequencies have been tentatively assigned in terms of C_2V symmetry, based upon Raman polarization data and analogies with the spectra of maleimide and maleic anhydride. A force field was derived by initially transferring force constants from maleimide. After small iterations a satisfactory correspondance was achieved between the observed and calculated in-plane modes whereas larger discrepancies remained for some of the out-of-plane vibrations.     

The vibrational spectra of n-dodecyl methacrylate

Spectra of n-dodecyl methacrylate are given from 4000 to 40 cm⁻¹ in the i.r. and 3000 to 150 cm⁻¹ in the Raman spectrum. Of the 138 fundamental modes expected on the basis of C_s symmetry, 58 were assigned. Combination and overtone modes were calculated but not all could be discerned.     

The vibrational spectra of cyclobutanecarboxylic acid

The complete vibrational spectra of crystalline cyclobutanecarboxylic acid have been recorded. A tentative, approximate vibrational assignment is proposed based on these spectra and the infrared spectra of the potassium salt, cyclobutanecarboxylic acid-O-d, cyclobutanecarboxylic acid-α-d-O-d, cyclobutanecarboxylic acid-α-d and previous published results with other simple cyclobutane derivatives.     

The vibrational spectra of mellitic trianhydride

The IR and Raman spectra of mellitic trianhydride have been reported in the frequency region from 2000-150 cm^?1, for the polycrystalline sample. Applying the selection rules to the CO stretching vibrations, the molecular structure of mellitic trianhydride has been discussed. The observed frequencies have been tentatively assigned considering a proposed D_3h structure.     

The vibrational spectra of hexafluorocyclobutene and 1,2-dichlorotetrafluorocyclobutene

Infra-red spectra of hexafluorocyclobutene and 1,2-dichlorotetrafluorocyclobutene were recorded in the region 4000-50 cm⁻¹ in the vapour phase, in solution and as amorphous and crystalline solids at ca 90 K. Raman spectra of the liquids, including semiquantitative polarization measurements, of the amorphous and crystalline solids at ca 90 K, and of gaseous hexafluorocyclobutene at room temperature were recorded. The fundamental frequencies of both compounds were assigned in terms of C_2υ symmetry, although small deviations from this symmetry cannot be excluded.     

The vibrational spectra of maleimide and N-D maleimide

The infrared spectra of maleimide as a vapour (160°C), melt (100°C), oriented polycrystalline film, pellet and when dissolved in various solvents were recorded between 4000 and 400 cm^?1. Also certain spectra in the far infrared region 400-40 cm^?1 were obtained. Raman spectra of the crystalline solid, melt and as a saturated solution in acetonitrile were recorded and semiquantitative polarization measurements carried out. For N-D maleimide infrared and Raman spectra of the solid compound were recorded.The fundamental frequencies have been assigned in terms of C_2v, symmetry on the basis of infrared vapour contours and dichroism of the oriented film as well as on Raman polarization data. A force field was derived for maleimide, by initially transferring force constants from maleic anhydride and subsequent refinement of the force constants. The agreement between observed and calculated frequencies for the in-plane modes was satisfactory whereas certain large discrepancies remained for the out-of-plane vibrations.     

The vibrational spectra and conformation of 1,2-dicyanotetrafluoroethane

Infrared spectra of 1,2-dicyanotetrafluoroethane have been recorded in the vapour, glassy solid, and crystalline solid states. Raman spectra have been recorded of the liquid and the crystalline solid. The trans form is shown to exist alone in the crystal, while trans and gauche forms co-exist in the vapour, liquid and in the amorphous solid with the trans conformer dominating.Complete vibrational assignments are proposed for the trans and for the gauche conformers. The latter in particular places heavy reliance upon the normal coordinate calculations.     

The vibrational spectra of strontium and barium diarsenates

The infrared and laser-Raman spectra of crystalline Sr₂As₂O₇ and Ba₂As₂O₇ are reported and discussed. The principal force constants for the As₂O₇^4? ion are calculated using a simplified molecular model.     

The vibrational spectra of some metal hyponitrates

The Raman spectrum of Na₂N₂O₃ and the i.r. spectra of Na₂N₂O₃, CaN₂O₃, BaN₂O₃, CdN₂O₃ and PbN₂O₃ are reported and assigned.     

The vibrational spectra of crystalline pyruvoyl chloride

The complete vibrational spectra of crystalline pyruvoyl chloride have been recorded and analyzed. This compound is an unstable liquid at room temperature. It was synthesized by a known procedure and all sample handling and data gathering were carried out at low temperatures. As an aid to the assignment, pyruvoyl bromide, also an unstable liquid at room temperature, was synthesized and its low temperature i.r. spectra was recorded. A tentative vibrational assignment is proposed and this assignment and the structure of pyruvoyl chloride are compared to those of other molecules of the pyruvate class.     

The conformation and vibrational spectra of isocyanato and isothiocyanatocyclohexane

The IR spectra of isocyanato and isothiocyanatocyclohexane (C₆H₁₁NCX) as liquids and as amorphous and crystalline solids at low temperatures have been recorded in the region 4000-50 cm^?1. High pressure (0–30 kbar) IR spectra of the neat samples were obtained in a diamond anvil cell and various high-pressure solid phases were studied. Raman spectra of the compounds as liquids and as low-temperature solids were obtained.Isocyanatocyclohexane crystallized directly as anisotropic solids containing equatorial molecules at low temperature and axial molecules at high pressure. Isothiocyanatocyclohexane formed a possibly plastic phase between 225 and 260 K where both equatorial and axial conformers are present. A solid high-pressure phase (1–3 kbar) at ambient temperature appeared anisotropic and contained both the e and a conformers. Below 225 K (atmospheric pressure) and above 10 kbar (ambient temperature) anisotropic crystals were formed which both contained equatorial conformers only.Normal coordinate analyses were carried out for the equatorial and axial conformers of the two molecules with different orientations (C_s and C_l symmetries) of the side chain. Force constants were transferred from various halo and pseudohalocyclohexanes. Tentative assignments of the fundamentals belonging to both the e and a-conformers are presented.     

The computed force constants and vibrational spectra of toluene

The complete harmonic force field and dipole moment derivatives have been computed for toluene at the Hartree-Fock level using a 4-21G basis set. The six scale factors optimized for benzene were used to scale the computed harmonic force constants of toluene. The vibrational frequencies of toluene computed from this scaled quantum mechanical force field are quite good. After a correction was made to two previously proposed spectral assignments, the mean deviation from the experimental frequencies is only 7.8 cm^?1 except for the frequencies related to the methyl group. Five more scale factors for the vibrational modes of the methyl group were reoptimized. The final comparison showed an overall mean deviation of 7.5 cm^?1 between the theoretical spectrum and the experimental spectrum. Computed intensities are qualitatively in agreement with experiments. They are highly useful in the investigation of questionable assignments.     

The vibrational spectra of 1,1,4,4-tetrafluoro- and 1,1,4,4-tetrachlorobutadiene

Raman data are reported for gas, liquid and solid 1,1,4,4-tetrafluorobutadiene, F₂CCHCHCF₂, and IR data for gas and solid. The molecule has a planar trans conformation of C_2h symmetry. With the aid of Raman depolarization ratios and IR band contours, twenty of the twenty-four spectroscopically-active fundamentals can be assigned with assurance. Frequencies are suggested for the remaining four modes.Raman and IR data are reported for the liquid and solid 1,1,4,4-tetrachlorobutadiene. Mid-IR gas phase data are also reported. Again the data can be satisfactorily explained under C_2h symmetry. Fourteen fundamentals can be assigned with confidence. Suggestions have been made for the frequencies of nine other fundamentals.     

The vibrational spectra and normal coordinate analysis of tetracyclopropyllead

All the fundamental frequencies observed in IR and Raman spectra have been assigned to the normal modes of the molecule (C₃H₅)₄Pb (C₃H₅ = cyclopropyl). The calculated force field is compared to that of (C₃H₅)₂Hg and the Cmetal stretching force constants are discussed along with those of Me₄Pb and Me₂Hg; The similarity of the spectra of cyclopropyllead and cyclopropyl-mercury proves that the vibrations of cyclopropyl structural units are isolated in both molecules.