Raman and infrared spectra of crystalline fluoroform

Raman and far-infrared spectra of crystalline fluoroform at temperatures between 20 and 106 K have been recorded. There is no evidence for any solid-state phase transitions, nor for hydrogen bonding. The rich lattice spectra and crystal field splittings suggest that the unit cell is rather large, and possible structures are discussed.     

Raman and infrared spectra of crystalline chloroform

Raman and far-infrared spectra of polycrystalline samples of chloroform at 20 and 80 K are reported. Crystal field spilttings of the intramolecular fundamentals are observed as well as nine Raman and six infrared lattice modes. Spectra are interpreted in terms of a group theoretical analysis based on the molecular and crystal symmetries.     

The polarized infrared and Raman spectra of crystalline ammonium trifluoromethanesulphonate

The infrared and Raman spectra of NH₄CF₃SO₃ were obtained and analysed and an assignment was proposed for the observed bands. The assignment of some anion bands was supported by means of the polarized spectra of monocrystals. The fundamental frequencies of the anion were used for a normal coordinate calculation.     

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.     

The effect of high external pressures on the infrared and Raman spectra of crystalline tetra-n-propylammonium bromide

The infrared and Raman spectra of crystalline tetra-n-propylammonium bromide, (n-C₃H₇)₄NBr, have been measured in the 3000 – 700 cm⁻¹ region and vibrational assignments are proposed in part on the basis of the known crystal structure. Pressure-tuning infrared and Raman studies of this material were also undertaken using a diamond-anvil cell. There is a pressure-induced phase transition occurring between 1.8 and 2.1 GPa, which is most likely a second-order transition. Some differences are noted between the infrared data reported here and those given in an earlier high-pressure infrared study. The spectroscopic results will be useful in examining zeolites involving (n-C₃H₇)₄NBr as a template.     

The effect of high external pressures on the infrared and Raman spectra of crystalline tetra-n-propylammonium bromide

The infrared and Raman spectra of crystalline tetra-n-propylammonium bromide, (n-C₃H₇)₄NBr, have been measured in the 3000 – 700 cm⁻¹ region and vibrational assignments are proposed in part on the basis of the known crystal structure. Pressure-tuning infrared and Raman studies of this material were also undertaken using a diamond-anvil cell. There is a pressure-induced phase transition occurring between 1.8 and 2.1 GPa, which is most likely a second-order transition. Some differences are noted between the infrared data reported here and those given in an earlier high-pressure infrared study. The spectroscopic results will be useful in examining zeolites involving (n-C₃H₇)₄NBr as a template.     

The infrared and Raman spectra of guanidinium salts

The i.r. and Raman spectra of guanidinium chloride, guanidinium perchlorate, and the deuterated derivatives of these salts, have been determined as solids and in solutions.     

The infrared and Raman spectra of pyromellitic dianhydride

The infrared and Raman spectra of solid state samples of pyromellitic dianhydride have been measured. The infrared—Raman mutual exclusion rule has been observed and the frequencies have been tentatively assigned on the basis of D_2h symmetry. The values of the CO and skeletal ring stretching frequencies have been interpreted in terms of a conjugated π-system.     

The infrared and Raman spectra of carbonyl diisocyanate

The infrared and Raman spectra of carbonyl diisocyanate have been recorded. Vibrational assignments have been made on the basis that two planar conformations are present both in the liquid and vapour phases: cis—cis and cis—trans. Simple normal coordinate calculations have been used to confirm the assignments.     

The infrared and Raman spectra of trans- and cis-tetrachloro-tetramethylbicyclopropylidene

The title compounds trans- and cis-2,2,2',2'-tetrachloro-3,3,3',3'-tetramethyl-bicyclopopylidene were synthesized, and their infrared and Raman spectra were recorded. Non-coincidence between the IR and Raman bands of the trans compound suggested C(2h) symmetry and a planar ring system. In the cis compound most of the IR and Raman bands coincided and a C(2v) symmetry seems likely. The exocyclic CC double bond gave rise to a medium/weak Raman band at 1,847 cm(-1) in the trans compound. In the cis derivative IR and Raman bands both at 1,825 cm(-1) were observed. From similarities with related molecules, the ring breathing, the antisymmetric ring stretch, the CCl(2) out-of-phase and in-phase stretch and the out-of-plane ring bending modes have been tentatively assigned for the trans and cis compounds.     

The infrared and Raman spectra of octachloro- and octabromocyclotetrasilane

The infrared and Raman spectra of cyclo-Si₄Cl₈ and cyclo-Si₄Br₈ have been measured and assigned. The selection rules indicate that the Si₄ ring is not planar. A normalcoordinate analysis (NCA) has been performed. The SiSi stretching-force constants are calculated to be 1.75–1.5·10² Nm^?1 and are lower than in the corresponding perhalogenated five- and six-membered rings. The SiCl and SiBr force constants seem to be somewhat higher (2.7–2.35·10² Nm^?1).     

The Fourier Transform Raman and infrared spectra of naphthazarin

The FT Raman spectra of the three naphthazarin polymorphs have been recorded for the first time and compared with the FTIR spectra of the polymorphs and of naphthazarin with deuterated hydroxyl groups. It is possible to distinguish between the polymorphs, to deduce that the room temperature static symmetry point group of naphthazarin is C_2v, to assign the ν(CH), σ(OH), γ(OH) vibrations and to confirm the absence of the ν(OH) mode.     

Raman spectra of ordered crystalline ethane

The Raman spectrum of ethane in phase II at 74 K has been obtained. The spectrum lends support to the crystal structure previously deducted from i.r. spectra.     

The molecular structure and infrared and Raman spectra of SCCCS

The structure, rotational constants, and vibrational spectra of SCCCS have been predicted by ab initio and density functional quantum mechanical methods. Basis sets ranging in size from double-ζ plus polarization (DZP) to triple-ζ plus double polarization, augmented with f functions (TZ2Pf) were employed. Our theoretical results are in agreement with experiments for both the geometrical structure and most of the fundamental frequencies that have been observed. An exception occurs for the SCC bending frequency υ₅, for which the 1966 and 1972 assignments of Bates and Smith appear superior to the 1966 Smith and Leroi Raman assignment, accepted in the definitive recent studies of Holland and Winnewisser. We present results for four isotopomers of SCCCS that have not yet been observed in the laboratory.     

Raman and infrared spectra of lanthanum molybdate

The infrared and Raman spectra of gel-grown lanthanum molybdate were recorded. Group theoretical analysis was carried out and a vibrational assignment proposed based on C_2h symmetry. Factor group and site effects are discussed.     

The infrared and Raman spectra of 2,4-and 2,5-dimethylbenzaldehydes

The vibrational frequencies of 2,4-and 2,5-dimethylbenzaldehydes have been reported from the study of ir absorption and Raman spectra of these molecules recorded in liquid phase. The probable assignments for all the frequencies are presented in terms of the fundamentals, overtones or combinations