Vibrational spectra of cyanosubstituted cyclopropanes—III. Cyanocyclopropane and cyanocyclopropane-1-d1

The vibrational spectra of cyanocyclopropane have been reinvestigated with the gas phase i.r. spectrum reported for the first time. The i.r. spectra of cyanocyclopropane-1-d₁ have been measured from 4000 to 200 cm⁻¹ in the liquid and the gaseous phases and from 4000 to 400 cm⁻¹ in the polycrystalline state. Raman spectra of the liquid down to 50 cm⁻¹ were obtained. A vibrational assignment of all fundamentals is proposed. With the present data, we had to reassign several fundamentals published in the literature.     

Vibrational spectra of halogen substituted cyclopropanes—V. Trans-1,2-dichlorocyclopropane

The i.r. spectra of gaseous trans-1,2-dichlorocyclopropane were measured from 4000 to 400 cm⁻¹ and to 200 cm⁻¹ in the liquid phase. The Raman spectrum of the liquid was obtained from 4000 to 50 cm⁻¹. An assignment of all 21 normal vibrations was proposed on the basis of i.r. vapour phase band contours, Raman depolarization ratios, expected group frequencies and comparison with closely related molecules. There is excellent agreement with the normal modes previously assigned for the cis and trans isomers of the chloro, bromo and iodo analogues. The data indicate little interaction between the two CHCl moieties.     

Vibrational spectra and normal coordinate calculations for trimethylselenonium-d0 and -d9 ions and dimethyl selenide-d0, -d6

The i.r. (4000-30 cm⁻¹) and Raman (4000-0 cm⁻¹) spectra of trimethylselenonium iodide and dimethyl selenide have been obtained, together with those of their deuterated analogues. All the active fundamentals of the trimethylselenonium ion have been assigned, assuming C_3ν molecular symmetry. Normal coordinate calculations have been carried out for the trimethyl-selenonium ion and dimethyl selenide and the SeC force constants of both the compounds are compared, including those of other corresponding chalcogenides.     

Vibrational spectra and normal coordinate calculations for dimethyltelluride-d0, -d6 and dimethyltellurium difluoride-d0, -d6

The i.r. (4000-30 cm⁻¹) and Raman (4000-O cm⁻¹) spectra of dimethyltelluride, dimethyltellurium difluoride and their deuterated analogs have been obtained. All the active fundamentals of these compounds except methyl torsions were assigned, assuming a C_2υ molecular symmetry for both the tellurides. Normal coordinate calculations have been made in order to confirm the proposed assignments. The skeletal bond strength of the tellurides together with that of TeF₄ are discussed, using the valence stretching force constants.     

Torsional transitions and barrier to internal rotation of 1,2-butadiene

The far i.r. spectrum of 1,2-butadiene (methyl allene) has been recorded in the gas phase from 370 to 40 cm⁻¹ with a resolution of 0.1 cm⁻¹. The methyl torsional fundamental has been observed for the first time at 154.3 cm⁻¹, along with some accompanying torsional hot bands. From these data the barrier to internal rotation has been calculated to be 556 cm⁻¹ (1.59 kcal/mol). Detailed K-structure has also been observed for both A—A and E—E torsional transitions and considered in the analysis. SCF calculations have been made for the structure and energies of conformers, so that both kinetic and potential constants for internal rotation have been obtained. The a′ skeletal fundamental is observed at 201.8 cm⁻¹ as a much stronger band than the torsional mode, and the a″ skeletal fundamental gives rise to an even stronger band at 319.8 cm⁻¹.     

Spectra and structure of organophosphorus compounds—XXX. Vibrational and conformational study of methoxy difluorophosphinoxide-d0 and -d3

The i.r. (4000-40 cm⁻¹) and Raman (4000-10 cm⁻¹) spectra of gaseous, liquid and solid methoxy difluorophosphinoxide, CH₃OP(O)F₂, and the deuterated analog have been recorded. Results obtained from variable solvent and matrix isolation studies are consistent with the existence of both trans (CO bond trans to the PO bond) and gauche (dihedral angle approximately 120° from the trans form) conformers in the fluid phases. From simulations of observed gas phase i.r. band profiles, it was possible for assignments to be made to the individual conformers for a number of the fundamentals. Variable temperature studies carried out for the gaseous and liquid phases give energy differences between the gauche and trans conformers of 451 ± 100 cm⁻¹ (1.29 ± 0.3 kcal/mol) and 69 ± 20 cm⁻¹ (197 ± 57 cal/mol), respectively. Furthermore, these data are consistent with the gauche form being the thermodynamically preferred conformer for the gas phase whereas the trans conformer is preferred in the liquid phase and the only conformer present in the annealed solid. The methoxy torsional mode of the gauche conformer has been assigned to a very strong band observed in the far i.r. spectrum of the gas phase at 42 cm⁻¹. The matrix isolation spectra of the normal compound in Ar, CO and N₂ matrices indicated no changes in the conformational equilibrium among these different matrices and this equilibrium remains unchanged upon annealing the matrices.     

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.     

Inelastic electron tunnelling spectra of 3- and 4-nitrobenzoic acids and nitrobenzene

Inelastic electron tunnelling spectra of 3- and 4-nitrobenzoic acids and nitrobenzene were measured in the range from 200 to 4000 cm⁻¹. The spectra were compared with that of benzoic acid. An approximate assignment of the spectral peaks was carried out by applying the assignments of benzoic acid and nitrobenzene based mainly on i.r. and Raman results. A broad band of the NH stretching mode (ca 3300 cm⁻¹) in the spectra of nitrobenzene and 3-nitrobenzoic acid implies a reaction between the adsorbent and hydroxyl groups on the surface of the alumina layer.     

F.t.i.r. and Raman spectra of triphenylphosphine,triphenylarsine, triphenylstibine,and dibenzylsulphide

The f.t.i.r. and Raman spectra of triphenylphosphine, triphenylarsine, triphenylstibine, and dibenzylsulphide in the solid state at ca 80 K have been recorded over the ranges 3500-40 cm⁻¹ (infra-red, 1 cm⁻¹ resolution) and 1650-30 cm⁻¹ (Raman, 2 cm⁻¹ resolution). The data, particularly those in the low wavenumber region, are more extensive, more complete, and of higher quality than those obtained in previous studies. Detailed band assignments are given.     

Spectroscopic studies on crotonyl chloride and dimethyl acryl chloride

Infrared spectra of liquid samples of crotonyl chloride and dimethyl acryl chloride in the region 4000-600 cm⁻¹ have been recorded along with the Raman spectra in the region 4000-100 cm⁻¹. From CNDO/2 results and some band splitting, existence of conformers are inferred. A complete assignment of the spectra is made on the basis of reported spectral studies on related compounds and the relative variation of i.r. peak intensity with solvent polarity. Normal coordinate analysis of crotonyl chloride has been carried out for the first time.     

Etude de l'acridinone par spectrometries i.r. et Raman: C13H9NO et C13H8DNO

The i.r. and Raman spectra of polycrystalline acridinone and N-deuterated derivatives have been investigated between 4000 and 200 cm⁻¹; solutions in various solvents were also examined. An assignment for intramolecular fundamentals is given in terms of group frequencies and symmetry type. The strength and characteristics of the NH⋯O hydrogen bonds are discussed as well as the crystal structure.     

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.     

Infrared spectroscopic study of copper(II) complexes with N-substituted tetrazoles

The i.r. spectra (4000-200 cm⁻¹) of N-alkyltetrazoles and their complexes with copper(II) salts CuCl₂ and Cu(NCS)₂ have been measured. Spectral criteria in the middle and far regions for the identification of tetrazole isomers and their complexes are proposed. The site of the coordination in a tetrazole molecule and supposed structure of complexes are being discussed.     

Asymmetric torsional potential function and conformational analysis of furfural by far infrared and Raman spectroscopy

The far i.r. (400-50 cm⁻¹) spectra of gaseous and solid furfural (2-furancarboxaldehyde), c-C₄H₃O (CHO), have been recorded. Additionally, the Raman (3500-20 cm⁻¹) spectra of the gas and liquid have been obtained at variable temperatures and the spectrum of the solid at 25 K. These data have been interpreted on the basis that the molecule exists in two different conformations in the fluid states and that the conformation which has the two oxygen atoms oriented in a trans configuration, OO-trans, is most stable (ΔH ⩽ 1 kcal/mol) in the gas; however, the conformation which has the two oxygen atoms oriented cis, OO-cis, is preferred in the liquid (ΔH = 1.07 ± 0.03 kcal/mol) and is the only rotamer present in the spectra of the solid. The asymmetric torsional fundamental for the OO-trans rotamer has been observed at 146.25 cm⁻¹ in the far i.r. spectrum of the vapor and has five accompanying “hot bands”. The corresponding fundamental for the OO-cis rotamer has been observed at 127.86 cm⁻¹ along with a “hot band” which occurs at 127.46 cm⁻¹. From these data a cosine-based potential function governing internal rotation of the CHO top has been determined and the potential coefficients have values of V₁ = 173 ± 2, V₂ = 3112 ± 20, V₃ = 113 ± 2 and V₄ = −198 ± 6 cm⁻¹. This potential is consistent with an enthalpy difference between the more stable OO-trans and high energy OO-cis conformers being 286 ± 24 cm⁻¹ (818 ± 67 cal/mol) and a trans to cis barrier height of 3255 ± 20 cm⁻¹ (9.31 ± 0.06 kcal/mol). These results are compared to the corresponding quantities obtained previously from microwave spectroscopy and theoretical methods.     

Infrared and Raman study of alunite—jarosite compounds

Infrared and Raman spectra of alunite and jarosite compounds, AR₃(SO₄)₂(OH)₆, where R is either Fe³⁺ or Al³⁺ and A is a monovalent cation, have been obtained between 4000 and 40 cm⁻¹. The observed number and position of the i.r. and Raman bands have been analysed under the centrosymmetric D⁵_3d space group. In addition, some relationships between the crystallochemical characteristics of these compounds and their vibrational properties are presented.     

Structure,vibrational assignment,normal coordinate analysis,and ab initio calculations of methylisocyanate

The infrared (3200-30 cm⁻¹) and Raman (3200-10 cm⁻¹) spectra of gaseous and solid methylisocyanate, CH3NCO, have been recorded. Additionally, the Raman spectrum of the liquid has been obtained and qualitative depolarization ratios have been measured. The CNC bend has been observed in the far infrared and low frequency Raman spectra of the gas at approximately 172 cm⁻¹. An additional far infrared band at ≈50 cm⁻¹ has tentatively been assigned as the methyl torsional mode, although it could be due to the Δν = 1, Δl = ± 1 transitions of the CNC bending mode. A complete assignment of the vibrational fundamentals is proposed. The structural parameters, force constants, and vibrational frequencies have been determined from ab initio Hartree—Fock gradient calculations using the 6-31G* basis set. Additionally, structural parameters have been obtained with the 6-311 + + G** basis set with electron correlation at the MP2 level which are compared to those obtained from the microwave data and electron diffraction study. These results are compared with the corresponding quantities obtained for similar molecules.     

Vibrational spectroscopic analysis of lithium hydrazinium sulfate

The low temperature polarized Raman spectra of lithium hydrazinium sulfate, LiN₂H₅SO₄, have been measured in the range 5–3500 cm⁻¹. The symmetry-based assignments for the observed modes are given. The room temperature polarized i.r. reflectivity spectra in the range 200–4000 cm⁻¹ were also measured to verify the presence of extensive TO—LO splitting in the sulfate ion ν₃ and ν₄ internal optic modes. In the lattice mode region, the lithium ion external optic modes are identified, and the spectra of the deuterated analog allow the identification of several modes due primarily to the external motions of either the sulfate or hydrazinium ions. Other lattice modes are found to be a mixture of sulfate and hydrazinium ion external motions. Coupling of the sulfate ion ν₃ modes and the hydrazinium ion group bending modes prevents an unambiguous assignment of the bands in the 1050–1200 cm⁻¹ spectral region. The N—H stretching region spectra contain a larger number of modes than predicted by a factor group analysis. These extra modes are discussed in terms of resonance interactions of the N—H stretching fundamental modes with overtones and combination modes.     

Polarized infrared spectra of KHSeO4 single crystal

The polarized absorption i.r. spectra of KHSeO₄ single crystal were measured in the 4000-300 cm⁻¹ region at 300 and 25 K and discussed in relation to the crystal structure. The results obtained are compared with the spectra of the isomorphous KHSO₄ crystal.     

Spectres de vibration de pigments rouges de la famille des quinacridones

The i.r. and Raman spectra of various crystalline phases of the trans linear quinacridone and some methylated and chlorinated derivatives have been investigated between 4000 and 200 cm⁻¹. Each of these pigments has been characterized spectroscopically and an assignment for intramolecular fundamentals is given in terms of group frequencies. The strength and length of NH ⋯ O hydrogen bonds have been assessed from the vNH frequency and correlated with the pigment colour which is principally determined by intermolecular interactions rather than by the substituent hypso(batho)chromic effect. The NH ⋯ O distance increases from 2.87 Å for the red compounds to 2.93 Å for the purple ones.     

Spectra and structure of silicon compounds. XVII Raman and infrared spectra and vibrational assignment for hexamethyldisilane and ab initio calculations for disilane and hexamethyldisilane

The IR spectra of gaseous and solid hexamethyldisilane between 4000 and 25 cm⁻¹ and the far-IR spectrum of the liquids from 450 to 25 cm⁻¹ have been recorded. The Raman spectra have been recorded from 3500 to 10 cm⁻¹ for all three physical phases. Assisted by ab initio calculations, the vibrational spectrum of hexamethyldisilane has been assigned under D_3d symmetry and the results of a normal coordinate analysis are discussed. No spectral features indicative of free internal rotation have been observed. Gradient ab initio calculations have been carried out for the disilane and hexamethyldisilane molecules using different types of basis sets. The structural parameters, rotational constants, unscaled and scaled frequencies and harmonic force constants have been reported for both disilane and hexamethyldisilane.