Conformational behaviour and vibrational spectra of cyclopropyl methyl ketone and methyl cyclopropyl-carboxylate

Infrared spectra in the vapour, liquid, and crystalline states and Raman spectra in the liquid and crystalline states have been obtained for cyclopropyl methyl ketone and for methyl cyclopropylcarboxylate. In cyclopropyl methyl ketone, the dominant conformer in the liquid and vapour states, the cis, has been shown to exist exclusively in the crystal. In methyl cyclopropylcarboxylate, the conformer dominant in the liquid and vapour states has been demonstrated to exist in the crystal. Vibrational assignments are made for the ring modes and for those modes which are sensitive to conformational changes.     

Conformational behaviour and vibrational spectra of cyclopropylcarbinol and 1-cyclopropylethanol

Infrared spectra in the vapour, liquid and crystalline states as well as in dilute CCl₄ solution, and Raman spectra in the liquid and crystalline states were recorded for cyclopropylcarbinol and 1-cyclopropylethanol. Some weak vibrational bands present in the spectra of the vapours, liquids and solutions vanished in the crystalline solids. The spectra of each compound have been interpreted in terms of an equilibrium between a stable conformer, dominating in the vapour and liquid states and exclusively present in the crystals and one or more other conformers of small abundance. Vibrational assignments are presented for the ring modes and for those modes which are sensitive to conformational changes.     

The conformation and vibrational spectra of 1,5-hexadiene-3-yne (divinylacetylene) and perchloro-1,5-hexadiene-3-yne (perchlorodivinylacetylene)

Infrared spectra of 1,5-hexadiene-S-yne (divinylacetylene) have been recorded in the vapour phase, in solution and in the amorphous and crystalline solid states at 90 K in the region 4000–4020 cm^?1. Correspondingly, IR spectra ofperchloro-1,5-hexadiene-3-yne (perchlorodivinylacetylene) as a melt, as a solute in various solvents and as a solid at 90 K have been obtained. Raman spectra of the two compounds were recorded in the liquid (molten) state including polarization measurements, and as crystalline solids at 90 K.The spectral data indicate that each compound exists as one conformer only in the various states of aggregation. In divinylacetylene the molecular symmetry appears to be anti (C_2h) while for perchlorodivinylacetylene the symmetry is either C_2v (syn) or C₂ (gauche). Vibrational assignments for the spectra of both molecules are presented and the values are compared with the results of normal coordinate analyses.     

The vibrational spectra of 1,1,2-trichloro-3,3-difluoro-1-propene

The infrared spectra of 1,1,2-trichloro-3,3-difluoro-1-propene (CCl₂CClCHF₂) as a vapour, liquid and crystalline solid were recorded in the region 4000-50 cm⁻¹. Raman spectra of the liquid, as a solute in various solvents and as an unannealed and annealed crystalline solid at 90 K were obtained.No significant spectral changes occurred between the vapour, liquid and crystalline states, and the spectra strongly suggested one conformer with more than 95% abundance, probably of C_s, symmetry. The fundamental frequencies have been assigned and the values agree well with the results of a force constant calculation.     

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.     

Conformation and vibrational spectra of 1,5-hexadiyne (bipropargyl)

The infrared spectra of 1,5-hexadiyne (bipropargyl) as a vapour, liquid and crystalline solid and in several solvents have been recorded. Raman spectra were obtained for the liquid (including polarization measurements), the crystal and for several solutions.The data were interpreted in terms of two conformers, trans and gauche, in the vapour and liquid states and one, the trans, in the crystalline form. Interpretation of the spectra in terms of the conformational equilibria was not straightforward, and firm conclusions could not be drawn from the spectra alone. Vibrational assignments were made, supported by normal coordinate calculations.     

Spectroscopic studies of 1,4-dibromobutyne-2

Infrared spectra of 1,4-dibromobutyne-2 have been recorded over the 4000-200 cm^?1 region in the vapour, liquid, amorphous and crystalline states Raman spectra were extended to ca. 20 cm^?1 in the same states of aggregation, except for the non-recorded vapour phase spectrum. The temperature was varied between ?190 and 160 °C, and the pressure up to 10 kbar.A high proportion of the molecules exhibited free, internal rotation in the vapour and liquid phases, but to a smaller extent in the amorphous state at ?190 °C. For those molecules not being excited beyond the potential barrier, an unsymmetric conformation was preferred, whereas in the crystalline state the molecules possessed the anti conformation (C_2h) both at low temperature and at high pressure at ambient temperature.A vibrational analysis based upon force field calculations was carried out and the mean amplitudes of vibration computed. The data have been related to preliminary results from dipole moment and electron diffraction investigations.     

Vibrational and conformational analysis of chloromethylacetate and some deuterated derivatives

The i.r. spectra of gaseous, amorphous and crystalline solid and the Raman spectra of liquid and amorphous solid chloromethylacetate, CH₃COOCH₂Cl, and three deuterated derivatives, CH₃COOCD₂Cl, CD₃COOCH₂Cl and CD₃COOCD₂Cl, were obtained and an assignment proposed. Only one conformer of CMA was found to be present in all phases. Band contour simulation of the i.r. vapour phase bands showed this to be the s-cis gauche conformer. This was confirmed by a study of the partially deuterated compound CD₃COOCDHCl, of which the separate transitions originating from the antiperiplanar and synclinal isolated CH stretches were observed in the i.r. spectra of the vapour and crystalline solid and in the Raman spectrum of the vapour.     

Conformation and vibrational spectra of 1-bromo-1,5-hexadiyne (bromobipropargyl)

The IR spectra of 1-bromo-1,5-hexadiyne (bromobipropargyl) as a vapour, liquid and crystalline solid and in several solvents have been recorded. Raman spectra were obtained for the liquid (including polarization measurements) and the crystal.The data were interpreted in terms of two conformers, trans and gauche, in the vapour and liquid states and one, trans, in the crystal. The conclusion that the trans conformer was the one present in the crystal was based on several independent pieces of evidence. Vibrational assignments were made, supported by normal coordinate calculations.     

Raman spectra and structure of biphenyl isoatomers (the S0, S1, T1 states and the cation and anion radicals)

The Raman and transient resonance Raman spectra of biphenyl (BP) and its perdeuterated analogue (BP-d₁₀) in three different electronic states (S₀, S₁ and T₁) and in two different ionized states (cation and anion) have been recorded in solution. The S₀ Raman spectra have also been measured for the crystalline state. The obtained set of spectra are analysed on the basis of the established vibrational assignments for the ground state of the planar (crystal) and the non-planar (solution) structures. The analysis suggests that BP in solution exists as a twisted structure in the S₁ state, but that it takes planar or nearly planar structures in the T₁, the cationic and the anionic states.     

Vibrational spectra and rotational isomerism of triallyl amine

The infrared spectra of triallyl amine in the vapour and liquid phases (as solutions in CS₂, CCl₄, CH₃Cl and CH₃CN), and in the solid state at low temperature were measured from 250 to 4000 cm⁻¹. The Raman spectrum of the liquid was recorded and qualitative depolarization measurements were made. It is shown that in the liquid and vapour phases the molecule exists as a mixture of at least two rotational isomers, while in the crystalline phase it assumes a single configuration having point-group symmetry C₃. A vibrational assignment for the observed bands in the infrared and Raman spectra is proposed on the basis of the C₃ point group symmetry for the more stable form of the molecule.     

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.     

Apport de la coordination des hétérocycles a la connaissance de leurs spectres infrarouge et Raman. III—spectres de la méthyl-3 pyridine

The i.r. and Raman spectra of methyl-3 pyridine in the vapour, liquid and solid states and those of coordination compounds X_3-n[Ir(Me-3py)_nCl_6-n] with in = 1,2,3,4, have been investigated. A complete vibrational assignment is deduced for methyl-3 pyridine and compared with previous interpretations reported in the literature.     

Conformation and vibrational spectra of 1,5-hexadiyne (bipropargyl) and 1,5-hexadiyne-1,6-d2

The infrared spectra of 1,5-hexadiyne (bipropargyl) and 1,5-hexadiyne-1,6-d₂ as vapours, liquids, as solutes in various solvents and as crystalline solids at low temperatures and at high pressures have been recorded. Raman spectra were obtained for the liquids, including semiquantitative polarization measurements, and for the low temperature crystals.The data were interpreted in terms of two conformers, anti and gauche, in the vapour and liquid state and one, the anti, in the crystalline forms. A phase transition for 1,5-hexadiyne was observed at ca. 240 K. Both the high and low temperature crystals had molecules in the anti conformer.Interpretation of the spectra in terms of conformational equilibria was facilitated by a thorough vapour phase band contour analysis. With a few exceptions, all the vibrational fundamentals for both conformers were assigned and found to be in good agreement with results from normal coordinate calculations.     

Vibrational spectra and i.r. dichroism of p-bis(trimethylsilyl)benzene

Infrared spectra of p-bis(trimethylsilyl)benzene (PBTMSB) in the vapour phase, solutions, KI pellet and the polarized i.r. spectra of oriented crystalline films were recorded in the region of 4000-200 cm⁻¹. Raman spectra of this compound were investigated in the crystalline state and solutions. On the basis of vibrational spectra assignments of molecular vibrations are given. The internal vibrations of benzene ring can be treated according to D_2h and that of trimethylsilyl group according to C_3ν symmetry. The polarized i.r. spectra are discussed on the basis of the oriented gas model. A weak interaction of neighbouring molecules was observed in the case of the vibrations of the methyl groups. No band splitting was noticed for the benzene ring vibrations due to the crystal field effect.     

The vibrational spectrum of allene-d1

The i.r. spectra of allene-d₁ in the vapour phase and as a crystalline solid at 90 K were recorded in the region 5000-200 cm⁻¹. Raman spectra, including semi-quantitative polarization data, of the vapour and of the neat liquid, contained in a sealed tube at ambient temperature, were obtained. The fundamental frequencies were assigned in good agreement with results from earlier normal coordinate calculations.     

Vibrational spectra of the trans-trans and trans-cis conformers of dimethyl fumarate

Infrared and Raman spectra of dimethyl fumarate (DMFU) have been recorded in the temperature range 12–390 K. The solid state spectra are consistent with the trans-trans conformation. However, in the liquid phase (melt or solution in CCl₄) and in the vapour phase, additional infrared and Raman bands were observed due to the presence of the trans-cis conformer. For the trans-trans conformer the observed spectra have been assigned on the basis of a C_2h molecular symmetry. A normal coordinate analysis of trans-trans DMFU has been carried out using a modified Urey- Bradley force field to assist in the assignment. Observed frequencies for the trans-cis conformer have been assigned on the basis of a structure of C_s symmetry.     

The i.r., Raman and microwave spectra of 1-butene-3-yne (vinylacetylene) and 1-butene-3-yne-4d

The i.r. spectra of 1-butene-3-yne and 1-butene-3-yne-4d in the vapour phase and as crystalline solids at 90 K were recorded in the region 5000-100 cm⁻¹. Raman spectra, including semiquantitative polarization data, of the neat liquid and of the solid were obtained at 90 K. Microwave spectra of the compounds were recorded in the region 8–40 GHz at ambient temperature. Rotational transitions of the vibrational ground state and of the two lowest vibrational excited states v₁₃(a′) and v₁₈(a′') were measured.The fundamental frequencies of both compounds were assigned in excellent agreement with the results of normal coordinate calculations. Rotational fine structure was observed for several bands and interpreted as the Q-sub-branches of the perpendicular bands (in the symmetrical top approximation). For six bands the Q-sub-branches were assigned to the proper K-values. The Coriolis coupling constant ξ^a_13,18 was derived from the i.r. and from the microwave spectra.     

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.     

Vibrational spectra,assignments and normal coordinate analyses for crystalline zirconium tetrachloride and tetrabromide

Raman and far-IR spectra have been obtained of crystalline ZrCl₄ and ZrBr₄. The observed frequencies have been interpreted on the basis of the C_2h symmetry of the Bravais unit cell and have been subjected to a normal coordinate analysis. The interpretation and results are satisfactorily in accord with the X-ray structure.