Raman and i.r. spectra of 3-sulfolene

Raman and i.r. spectra of 3-sulfolene have been recorded and studied in the solid and liquid states. A vibrational assignment of the observed frequencies is proposed on the basis of the depolarization ratios of the Raman bands and of the dichroic ratios of the i.r. bands.     

Vibrational and conformational analysis of n-propylamine by means of i.r. spectroscopy and ab initio MO calculations

The gas-phase i.r. absorption spectra of normal and amino-deuterated n-propylamine were observed. Most of the observed bands were assigned with the help of ab initio MO calculations for the normal frequencies. The ab initio force constants were scaled to fit the observed spectrum by a least squares method. The existence of five rotational isomers is suggested from an analysis of the NH₂ wagging and torsion bands. The gauche-conformers about the CN axis are found to occupy about 70 % of all n-propylamine molecules, and the gauche-conformers about the CC axis are found to be more abundant than the trans-conformers.     

The i.r. and Raman spectra of solid trichloroacetonitrile

The i.r. and Raman spectra of polycrystalline films of CCl₃CN have been recorded at liquid nitrogen temperature. Chlorine isotope splitting has been resolved for the v₃ fundamental and crystal splittings have been observed for five of the fundamentals. A possible crystal structure is discussed. Raman wavenumbers and depolarization ratios are included for liquid CCl₃CN.     

Polarized laser Raman and i.r. spectra of dibenzyl sulphide

Polarized laser Raman and i.r. absorption spectra of dibenzyl sulphide have been investigated. Vibrational frequencies observed in both the spectra have been correlated and assigned to different normal modes of vibrations assuming C_s point group symmetry for the molecule.     

Raman and i.r. spectra of tetramethylcyclobutanedione and the fully deuterated derivative

Raman spectra of tetramethylcyclobutane-1,3-dione (TMCBD) as a polycrystalline solid and in solution in benzene and carbon tetrachloride have been recorded. Infrared and Raman spectra of the fully deuterated molecule have also been recorded. The spectra are consistent with predictions based on a centrosymmetric molecule with a planar cyclobutadione ring and point group D_2h. A fairly complete assignment of the observed spectra is presented for both molecules. A correlation of the frequencies of the fundamentals of TMCBD-h₁₂ and - d₁₂ has been made. Ground state frequencies of fundamentals involved in progressions in the n-π* electronic spectrum have been located.     

Comparative study of Raman and i.r. band widths of acetonitrile

Raman and i.r. band widths of all the vibrational bands of acetonitrile, CH₃CN and CD₃CN, have been measured in the pure liquid and in solutions of isotopic compounds. Widths arising from the vibrational relaxation, reorientational relaxation and resonance energy transfer have been separated on the basis of the current theories on vibrational band widths. The vibrational relaxation widths estimated for i.r. a₁ bands agree well with the observed isotropic Raman widths. Acceptable values of the rotational diffusion constants have been obtained from the band width data.     

Far i.r. and Raman spectroscopic studies of dimeric cyclopalladated compounds

The i.r. and Raman spectra (100–400 cm⁻¹) of seven dimeric cyclopalladated compounds are reported. The metallated ligands are azobenzene, N,N-dimethyl-benzylamine, phenylhydrazone acetophenone, N-phenyl, N-methyl hydrazone acetophenone, N-benzylacetophenone imide, benzo(h)quinoline and 8-methylquinoline. The spectral changes taking place on substitution of the Cl by Br, enabled the assignment of the bridged metal—Cl and Br frequencies, in this type of complex.     

Low-frequency vibrational Raman and i.r. spectrum of crystalline cystosine monohydrate

Raman scattering and i.r. transmission measurements were performed on oriented single crystals of cytosine monohydrate (CMH) at frequencies below 400 and 150 cm⁻¹ respectively. Frequency shifts caused by partial deuteration were also measured. The spectra were interpreted with the help of a lattice dynamical model containing only ‘line-of-sight’ interactions. The observed Raman frequencies in CMH were found to be significantly higher than corresponding ones previously measured in 1-methylthymine. These differences in frequencies are thought to be due to the additional hydrogen bonding provided by water molecules in CMH. A brief discussion is given of the implications of our measurements for interpyrimidine bonding in DNA.     

Polarized i.r. reflection and Raman spectra of sodium formate crystal

Polarized i.r. reflection spectra from the (010) and the (001) planes and polarized Raman spectra for the incident lights propagating along the ′a, the b and the c axes of single crystals of sodium formate were measured. The TO and the LO frequencies were determined for a number of the i.r. active intraionic and lattice modes. In both the i.r. and the Raman spectra, the frequency of the CH in-plane deformation mode ν₅ was proved to be higher than that of the CO₂ symmetric stretching mode ν₂. The TO—LO splittings of the intraionic modes were found to be correlated closely with the corresponding gerade-ungerade splittings and the i.r. absorption intensities.     

Infrared,matrix i.r. and Raman spectra of hexachloro-2-propanol

The i.r. spectra of the alcohol CCl₃CHOHCCl₃ have been recorded in the gaseous and solid phases, in argon, krypton, nitrogen and carbon monoxide matrices and in various solutions. Raman spectra of the solid alcohol and its solutions were also recorded. Assignments of the vibration bands are made on the basis of an approximate normal coordinate calculation. The alcohol exhibits two conformers in the vapour phase and in solutions; the relative stabilities of these conformers are discussed. When the temperature is varied, a reversible interconversion between two species of the alcohol occurs in nitrogen matrices. The self-association tendency of the alcohol is very weak.     

Raman studies of the effect of density of the fermi resonance in CO2

The effects of density on the Fermi resonance interaction in CO₂ up to 534 amagat density was investigated. The Raman intensity of the polarized, anisotropic, and isotropic components of the 2ν₂ and ν₁ bands was determined as a function of the fluid density. By using the theory of Fermi resonance coupling the ratio of the unperturbed Raman polarizability matrix elements of the 2ν₂ and ν₁ bands was determined as a function of the fluid density. Changes in the vibrational anharmonicity, and an increasing repulsion of the vibration levels were found to decrease the effectiveness of the resonance interaction as the fluid density was increased, therefore altering the Raman intensity and frequency with changing density.     

Raman and i.r.-emission studies of some tungstate- and molybdate- containing melts

Melts containing tungstate and molybdate ions have been studied using Raman and i.r.- emission spectroscopy. Vibrational data obtained for Mo¹⁶O₄²⁻- and Mo¹⁸O₄²⁻ containing melts firmly support a tetrahedral structure for MoO₄²⁻ (and by implication for WO₄²⁻ as well) and establish the correct assignment of ν₄ and ν₄ for this species. Acidification of these MoO₄²⁻ and WO₄²⁻ melts by addition of the corresponding metal trioxides produced no significant change in the observed spectra, although significant solubilities of the trioxides in the WO₄²⁻ and MoO₄²⁻ melts were observed.     

Interpretation of the i.r. and Raman spectra of chloropentamethylbenzene in the disordered room temperature phase

I.r. absorption and Raman scattering spectra of oriented and non-oriented single crystals of chloropentamethylbenzene were recorded at room temperature in the region 4000-200 cm⁻¹. Through a comparison of the different spectra in non-polarized light and in polarized light, we were able to assign the main vibration frequencies.     

Hydrogen scrambling in the long-lived protonated benzene ion generated from benzyl amine in the i.c.r. spectrometer

It is shown by reactions with various bases in an i.c.r. cell that an almost complete H-D randomization takes place in the gaseous and long-lived [C₆H₂D₅]⁺ ion, generated from C₆D₅CD₂NH₂ by electron impact, but not in its precursor ions. This follows from the ratio of [H]⁺ vs [D]⁺ transfer to bases, obtained from double resonance signals. The ratio appears to be reliable only if the protonated (deuterated) base is stable and does not undergo unimolecular decompositions.     

Hydrogen bonding effects on infrared and Raman spectra of drug molecules

Infrared and Raman spectra of three drug molecules, aspirin, caffeine and ibuprofen, in gas phase and in aqueous solution have been simulated using hybrid density functional theory. The long range solvent effect is modelled by the polarizable continuum model, while the short range hydrogen bonding effects are taken care of by the super-molecular approach with explicit inclusion of water molecules. The calculated spectra are found to compare well with available experimental results. The agreement obtained make grounds for proposing theoretical modeling as a tool for characterizing changes in the bonding environments of drug molecules in terms of particular variations in their IR and Raman spectra.     

Determination of the equilibrium constant of hydrogen bonding between substituted h-[d]-phenols and vinyl acetate in CCl4 by i.r. measurements

Equilibrium constants are reported for 26 light and 7 heavy phenols in terms of the usual equilibrium model of 1 : 1 complex formation. A solvation model sensitive to steric hindrance is also described. Linear correlations between log K_H and ΔνOH as well as log K_D and ΔνOH have been found for the interval: 30≤ΔνOH≤200 cm⁻¹. These allow estimates on the equilibrium isotope effect.     

Laser Raman and i.r. spectra of 2,4-, 3,4- and 3,5-dichlorobenzoylchlorides

The laser Raman and i.r. spectra of 2,4-, 3,4- and 3,5-dichlorobenzoylchlorides have been recorded and analysed. A complete assignment of vibrational frequencies has been proposed assuming C_s point group symmetry for these molecules. Complex carbonyl absorption has been noticed in the case of 2,4-dichlorobenzoylchloride and the same has been explained in terms of Fermi resonance.     

Raman studies of pressure tuning of the fermi resonance in solid CO2

Raman studies on the v₁, 2v₂ Fermi doublet in solid CO₂ up to 100 kbar at ambient temperature show the upper peak to increase and the lower peak to decrease both in intensity and frequency. It is concluded that the bare v₁ is above the bare 2v₂ at all pressures in solid CO₂.     

Interpretation of the i.r. and Raman spectrum of acetonitrile solutions of electrolytes in the CN stretching region

The effects of the cation—molecule interaction on the i.r. and Raman intensity of the CN stretching band in hydrogen cyanide are investigated. It follows from the calculated data that the cation—molecule interaction increases about 10 times the i.r. intensity of the CN stretching band, while the corresponding Raman intensity is slightly decreased. The present theoretical data for HCN and HCN … Li⁺ are utilized for the interpretation of the observed spectroscopic regularities in the i.r. Raman spectra of acetonitrile solutions of electrolytes.     

Vibrational (i.r. and Raman) spectra and conformational studies of 1-formyl-3-thiosemicarbazide

The i.r. and Raman spectra (30–4000 cm⁻¹) of 1-formyl-3-thiosemicarbazide (FTSC) and deuterated ftsc-d₄, have been studied. Most of the vibration modes reveal pairs of bands and show strong temperature dependence. A band group {ν(NNH₂)} at ∼ 1100 cm⁻¹ exhibits well resolved doublet (1095 and 1112 cm⁻¹) structure below 100 k. The intensity in the 11 12 cm⁻¹ band decreases regularly (band disappears at 150 K) with the rise in temperature. Two new bands at 955 and 1070 cm⁻¹ appear while measured above 400 K. The system eventually exists in several conformers in simultaneous equilibria. Moreover, a few bands {e.g. ν(CO), ν(CS) and ν(CH)} that show strong intensifies in i.r. exhibit weak (or zero) intensifies in the Raman and vice-versa. The features (characteristic of u and g vibration species) could be explained by a C_2h pseudo symmetry space group proposed for the system. Both the FTSC and FTSC-d₄ represent strong molecular associations. This favours the maximum abundance in the dimer stabilized conformers.