Vibrational spectra, structure, and theoretical calculations of 2-fluoro- and 3-fluoropyridine

The infrared and Raman spectra of liquid and vapor-phase 2-fluoropyridine and 3-fluoropyridine have been recorded and assigned. Ab initio and DFT calculations were carried out to compute the molecular structures and to verify the vibrational assignments. The observed and calculated spectra agree extremely well. The ring bond distances of the fluoropyridines are very similar to those of pyridine except for a shortening of the C-N(F) bond in 2-fluoropyridine. The C-F bond stretching frequencies are similar to that in fluorobenzene reflecting the influence of the ring π bonding.     

Vibrational spectra and structure of cis- and trans-1,2- dimethoxyethylenes

The vapor, liquid and CCl₄ solution infrared spectra of cis- and trans-1,2-dimethoxyethylene were recorded in the region 250–4000 cm^?1. The laser-Raman spectra were obtained in the liquid state only. The vibrational spectra show that at least two rotational isomers exist for each molecule. Further, the spectra indicate that for both the cis- and trans molecules, one of the rotational isomers has at least one planar conformer. Some vibrational assignments are made for the observed infrared and Raman bands of the cis- and trans- 1,2-dimethoxyethylenes.     

Vibrational spectra of 1,2-diaminobenzene, 4,5-dimethyl-1,2-diaminobenzene and catechol and their SER spectra

The Raman and IR spectra of 1,2-diaminobenzene and 4,5-dimethyl-1,2-diaminobenzene are reported and assignments of fundamental modes proposed. The surface-enhanced Raman spectra (SERS) of catechol, 1,2-diaminobenzene and 4,5-dimethyl-1,2-diaminobenzene on gold and silver colloids were obtained. FT-SERS of the three molecules are also briefly reported.     

Vibrational spectra and structure ofN,N-dinitromethylamine

The vibrational (IR and Raman) spectra ofN,N-dinitromethylamine were studied. The assignments of the bands were carried out using a comparison of spectra obtained in different aggregate states, invoking the results of normal coordinate analysis. The most probable symmetry of the molecule was shown to beC _s with a planar configuration of the N(NO₂)₂ moiety.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1503–1507, August, 1995.     

Vibrational spectra and rotational isomerism of 1,2-dimethyldisilane

The i.r. and Raman spectra of 1,2-dimethyldisilane and its Si-perdeuterated species have been measured for the liquid and solid states. Existence of rotational isomers about the SiSi bond was shown on the basis of the spectral examination and the normal coordinate treatment. The fundamental vibrations were assigned for the two possible rotational isomers.     

Vibrational spectra and structure of isopropylbenzene

Infrared spectra (4,000-400 cm(-1)) and Raman spectra (1,700-40 cm(-1)) of the liquid and two crystalline solids of isopropylbenzene (cumene) and isopropylbenzene-d(12) have been recorded. The spectra indicate that in the liquid and crystalline solids isopropylbenzene exists in planar conformation only (CH bond is in the plane of the benzene ring). An assignment of the observed band wave numbers both isopropylbenzene and isopropylbenzene-d(12) is discussed by comparison with normal mode wave numbers and IR intensities calculated from ab initio 6-31G (d) force fields.     

Vibrational spectra and structure of trinitromethane

The vibrational spectrum of trinitromethane was interpreted in terms of the additive interatomic interaction model on the basis of experimental infrared and Raman spectra of HC(NO₂)₃, DC(NO₂)₃, HC(¹⁵NO₂)₃ and normal coordinate analysis. The frequency assignment results were used in discussing its structure. It was shown that the symmetry of trinitromethane is below C₃ in the liquid state.     

Vibrational spectra and normal mode calculations of 1,2,5-telluradiazole

the vibrational spectrum of 1,2,5-telluradiazole is investigated in the 4000-50 cm⁻¹ region by i.r. and Raman spectroscopy. Infrared spectra of solid samples are also measured at 10 k.A satisfactory assignment of all the fundamentals is obtained by employing a valence force field which provided a complete set of normal coordinates suitable to describe the vibrational spectra of selenophene, tellurophene and 1,2,5-selenadiazole.Relations between the vibrational spectrum and the pseudopolymeric crystal structure of 1,2,5-telluradiazole are discussed.     

Vibrational spectra and crystal structure of ethyl methyl sulfide-mercury(II) chloride complex

The crystal structure of the ethyl methyl sulfide-mercury(II) chloride complex, CH₃SCH₂CH₃· HgCl₂, has been determined by X-ray diffraction. The conformation about the CS-CC axis of the complex is trans, which is different from the conformation of crystalline ethyl methyl sulfide. The Raman and IR spectra of the complex have been measured. Observed wavenumbers of the CH₂ rocking and C-C stretching vibrations of the complex are close to those of the trans form of ethyl methyl sulfide in the liquid state, but the wavenumber of the C-S stretching vibration shifts on formation of the S-Hg bond.     

Vibrational spectra and structure of sulfonium nitroimides

Vibrational spectroscopy and x-ray structure analysis have been used to investigate three new types of sulfonium nitroimides: N-nitrosulfylimides, N-nitrosulfoximides, and N,N-dinitrosulfodiimides. Structural parameters have been determined for the molecules , , and .Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2489–2496, November, 1991.     

Vibrational spectra,conformational equilibria,ab initio calculations and vibrational assignments of ethylmethylfluorosilane

The infrared spectra of ethylmethylfluorosilane (CH₃SiHFCH₂CH₃) have been recorded as a vapour, liquid and solid at 78 K in the 4000–50 cm⁻¹ range and isolated in an argon matrix at ca. 5 K. Infrared spectra of two different solid phases were obtained after annealing to temperatures of 120 and 130 K, and recooling to 78 K. Although the IR spectra were quite similar in the MIR region, certain differences were noted in the FIR region below 400 cm⁻¹. The most stable conformer MeMe was present after annealing to 130 K, but three bands belonging to MeH were detected after annealing to 120 K. Various infrared bands changed intensity when the argon matrix was annealed to temperatures between 20 and 35 K, and some of these were related to changes in the conformational abundance.Raman spectra of the liquid were recorded at room temperature and at various temperatures between 295 and 153 K. Spectra of an amorphous and annealed solid were recorded at 78 K. In the variable temperature Raman spectra, various bands changed in intensity and were interpreted in terms of conformational equilibria between the three possible conformers. Complete assignments were made for all the bands of the most stable conformer MeMe. From various bands assigned to the three conformers, the conformational enthalpy difference ΔH from MeMe to the intermediate energy conformer MeH was found to be 0.5 kJ mol⁻¹ and to the highest conformer MeF was 0.7 kJ mol⁻¹. At ambient temperature this leads to 39% MeMe, 32% MeH and 29% of the MeF conformer in the liquid.Ab initio calculations in the RHF, MP2, DFT approximations and very accurate G2 calculations were carried out. With one exception, the MeMe conformer had the lowest enthalpy in all these calculations, the MeH had the intermediate and the MeF the highest enthalpy, and the calculations were in good agreement with the measurements.     

Vibrational spectra and structure of symmetrical glyoximes

Conclusion Analysis of the vibrational spectra of symmetrical disubstituted glyoximes indicated that these are centrosymmetric molecules which exist, in all likelihood, in the trans-anti configuration.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2348–2351, October, 1986.     

Vibrational spectra and structure of triphenyltin halides

The solid state IR and Raman spectra of SnPh₃Br do not show any band at 338 cm⁻¹, and there is not C_3ν point group inversion between ν_as SnC₃ and ν_s SnC₃ for SnPh₃X (X  Cl, Br). The presence or absence of a band around 338 cm⁻¹ in the IR spectra of triphenyltin compounds cannot be used to distinguish between pyramidal and planar SnPh₃ groups.     

Vibrational spectra of cis- and trans-1,2-dimethyl-3-bromocyclopropane

The infrared and Raman spectra of cis- and trans-dimethylbromocyclopropane have been recorded from 4000 to 50 cm⁻¹. An assignment of the majority of the fundamentals is proposed and compared to those of related molecules. Definite and consistent trends in a number of normal modes of the ring and the methyl groups with the nature, position and number of the substituents have been found. Clear evidence has been obtained for steric interaction between the three substituents in cis-position.     

Vibrational spectra and structure of N,N′-dinitroalkylenediamines

Conclusions The vibrational spectra of N,N-dinitroalkylenediamines O₂NNH(CH₂)_nNHNO₂ (n=1–3) were analyzed, and a frequency assignment was made.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1530–1532, July, 1986.