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.     

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.     

Vibrational spectra of dimethyl aluminium hydride

The infrared and Raman spectra of dimethyl aluminium hydride and its partially deuterated isotopomers are reported and assigned. On the basis of variable temperature studies, coupled with isotope shifts and normal coordinate analysis, it is shown that the vapour phase infrared spectrum at room temperature may be interpreted as predominantly that of the dimer, with smaller amounts of trimer.     

Comparative study of infrared and Raman spectra of CCl4 in vapour and condensed phases: effect of LO-TO splitting resulting from hetero-isotopic TD-TD interactions

Salient features of an in-depth comparative study of infrared and Raman spectra of CCl(4) in vapour, liquid and condensed phases are presented. Wavenumbers of nu(4), nu(1)+nu(4), nu(3) and 2 nu(3) modes of CCl(4) vapour in infrared and Raman spectra are found to be in good agreement. Analysis of the vibrational spectra of liquid CCl(4) together with the spectroscopic observations on solid CCl(4) at low temperatures reveal TD-TD interaction amongst various CCl(4) isotopes in condensed states. The concept of LO-TO splitting of dipole active nu(3) and nu(1)+nu(4) Fermi doublet have been invoked to explain several features of the vibrational spectra of liquid CCl(4). There is significant strengthening of Fermi resonance interaction between nu(3) and nu(1)+nu(4) modes of CCl(4) in condensed phases relative to that in vapour phase. The Fermi resonance interaction parameter W has been found to be independent of molecular environment.     

The vibrational spectra and rotational isomerism of 1,1,1-Trimethoxyethane

The liquid, vapour and solid-state infrared spectra of 1,1,1-trimethoxy-ethane were recorded in the region 250–4000 cm⁻¹. The laser-Raman spectrum with qualitative depolarization data was obtained for liquid only. The spectra show that there are at least two rotational isomers present in the liquid phase. The solution spectra reveal that the less polar form is the more stable in the liquid phase. The form playing an important role has GGG configuration. A vibrational assignment has been attempted for the observed infrared and Raman bands.     

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.     

Infrared and raman spectra,conformation and force field of 3-methoxy propyne

The infrared spectra of 3-methoxy propyne (CH₃OCH₂CsolutionCH) in and in the crystalline and vapour states have been studied. The Raman spectra of 3-methoxy propyne and 3-methoxy propyne- 1-d have also been measured. The spectra are relatively simple, and no significant spectral alterations are revealed on conversion from vapour, to liquid, to the crystalline state. Together with vapour phase band contours and Raman polarization measurements this indicates that there is predominantly one conformer in all three states. An assignment has been proposed, based on a gauche conformation and supported by normal coordinate analysis.     

Polychlorobiphenyls differentiation and identification by gas chromatography/fourier transform infrared spectroscopy

Reference infrared vapour phase spectra of 20 polychlorobiphenyls (PCBs) have been obtained by gas chromatography/Fourier transform infrared spectroscopy (GC/FTIR). These spectra are consistent with those of PCB obtained by diffuse reflectance IR spectroscopy (DRIFT) and with those of more simple molecular structures (iodochlorobenzenes, 1-bromodichlorobenzenes). The IR frequencies of the GC/FTIR spectra of PCB are assigned in terms of substitution patterns. This work shows that GC/FTIR can be a good approach for differentiation and identification of PCB in complex mixtures.     

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 spectroscopic studies, conformations and ab initio calculations of 3,3,3-trifluoropropyltrichlorosilane

Infrared spectra of 3,3,3-trifluoropropyltrichlorosilane (CF3CH2CH2SiCl3) were obtained in the vapour, amorphous and crystalline solid phases in the range 4000-50 cm-1. Additional spectra in argon matrices at 5.0 K were recorded before and after annealing to 20-36 K. Raman spectra of the compound as a liquid were recorded at various temperatures between 298 and 210 K and spectra of the amorphous and crystalline solids were obtained. The spectra suggested the existence of two conformers (anti and gauche) in the fluid phases and in the matrix. When the vapour was shock-frozen on a cold finger at 80 K and subsequently annealed to 120-150 K, six weak or very weak Raman bands vanished in the crystal. Similar variations were observed in the corresponding infrared spectra after annealing and four very weak IR bands disappeared after crystallization. From intensity variations between 298 and 210 K of three Raman band pairs an average value Delta(conf)H degrees (gauche-anti)=6.1+/-0.5 kJmol-1 was obtained in the liquid. Annealing experiments indicate that the anti conformer also has a lower energy in the argon matrices. The conformational equilibrium is highly shifted towards anti in the liquid, and the low energy conformer also forms the crystal. The spectra of the abundant anti conformer and the few bands ascribed to the gauche conformer have been interpreted. Ab initio calculations at the HF/6-311G(**) and B3LYP/6-311G(**) gave optimized geometries, infrared and Raman intensities and vibrational frequencies for the anti and gauche conformers. The conformational energy differences derived were 11.8 and 9.2 kJmol-1 from the HF and the B3LYP calculations, respectively.     

Conformations and vibrational spectra of 2-chloro-3-fluoro-1-propene and 2-bromo-3-fluoro-1-propene

The infrared spectra of 2-chloro-3-fluoro- and 2-bromo-3-fluoro-1-propene as vapours and liquids were recorded in the region 4000–4050 cm^?1. Additional spectra of the amorphous and crystalline solids at ?170 °C and of the liquids in polar and non-polar solvents were recorded between 4000 and 200 cm^?1.Raman spectra, including semi-quantitative polarization measurements of the liquids were obtained. Spectra were also recorded with the samples dissolved in polar and non-polar solvents, and unannealed as well as annealed crystalline solids were studied at ?180 °C.Approximately 14 vibrational bands present in the spectra of the liquids, solutions and the glassy solids vanished in the infrared and Raman spectra of the crystals. From various criteria it can be concluded with certainty that the more polar (gauche) and less polar (cis) conformers were present in the crystalline chloro- and bromo- compounds, respectively. From infrared and Raman band intensities it was estimated that the conformational equilibrium in chlorofluoro-propene was highly displaced towards cis in the vapour, with both conformers approximately equally abundant in the liquid state (30 °C). For bromofluoro- propene the equilibrium was still further displaced towards the cis conformer.A striking similarity between the spectra of the two compounds was ob- served. The fundamental frequencies have been tentatively assigned and checked by force constant calculations. Dipole moments and relative stabilities of the conformers were estimated by a CNDO calculation.     

Comparative vapour phase FTIR spectra and vibrational assignment of manganese pentacarbonyls derivatives of the type XMn(CO)5: (where X=Br, Cl, I, H, D, CH3, CD3, CF3)

The infrared spectra of pure Mn(CO)(5)X in the region 4000-400 cm(-1) has been obtained in the vapour phase. The observed spectrum has been analyzed to distinguish the fundamental frequencies, the rotational-vibrational and structure, and overtone and combination frequencies. The assignment of the observed vapour phase frequencies to the fundamental modes of vibration has been made on C(4V) symmetry. The weak peaks due to XMn(CO)(4)((13)CO) molecules have been measured and assigned for all molecules. This study provides a comprehensive comparison of these compounds, with all of these data the assignment of frequencies is reviewed and a set of quite unambiguous assignments made. The significant finding in this regards are that, it is not necessary to assume lower than C(4V) symmetry for XMn(CO)(5) as has been done in previous consideration of some infrared spectrum of these compounds.     

Conformer assignment of OH stretches in ethanol and isopropanol

Rigid harmonic asymetric top contour simulation is applied to assign the OH stretch transitions observed in the vapour phase infrared spectra of ethanol and isopropanol to gauche and trans conformers. For hetanol, the high frequency ν(OH) absorption must be assigned to the trans, for isopropanol the high frequency absorption is found to be due to the gauche conformer.     

Infrared spectra and rotational isomerism of ethyl fluoroformate and ethyl propiolate

The infrared absorption spectra of ethyl fluoroformate and ethyl propiolate have been examined in the vapour, solution and solid states. For both esters evidence is found of rotational isomerism arising from internal rotation about the O-C₂H₅ bond, in close agreement with previous work on other ethyl esters.     

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.     

Rydberg bands in the UV spectrum of thiophene and its derivatives

The ultraviolet spectra of twelve halogenothiphenes have been recorded in the vapour phase. New transitions were observed in the region 45 000 to 50 000 cm⁻¹ which are absent in solution spectra and are assigned to Rydberg transitions. There is a good agreement of the band positions with those calculated from adiabatic ionization potential, using the quantum defect of thiphene. A study of the vibronic structure does not rule out the possible existence of two Rydberg-transitions. The vibrational frequencies of the fine structure are close to the observed values in the UP spectrum. The other members of the Rydberg series can be found in the far ultraviolet spectrum of thiophene.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Vibrational and electronic absorption spectra of some trisubstituted benzenes

Despite our studies on the Π* ← Π systems in some trisubstituted benzenes, the available data are limited, especially concerning two heavy and one light or one heavy and two light substituents. We therefore report and interpret the vapour phase electronic absorption, infrared and Raman spectra of 1-bromo-2,4-difluoro-, 1-bromo-3,4-difluoro-, 1-bromo-3,5-difluoro-, 1,3-dichloro-2-fluoro- and 1,3-dichloro-4-fluoro-benzenes.     

Synthesis of poly-L-naphthylalanine and its secondary structure

Polypeptides derived from L -naphthylalanine and γ-benzyl L -glutamate were prepared. Conformational properties in solution were investigated by circular dichroism (CD) and infrared spectra on the soluble copolymers, and the copolymers were assumed to take the right-handed α-helical conformation. By the addition of trifluoroacetic acid, a transition of side-chain arrangement is induced simultaneously with the conformational transition of the peptide backbone for the copolymer with the highest content of L -naphthylalanine residues. Fluorescence spectra of the copolymers show no excimer emission, which is evidence for the rigid orientation of the side-chain naphthyl groups. The infrared spectrum and x-ray diagram of poly-L -naphthylalanine do not rule out the helical conformation in the solid state.     

Pattern recognition applied to vapour-phase infrared spectra: characteristics of νOH bands

With the commercial availability of infrared spectrum libraries in computer accessible form, a new application of these libraries, the investigation of structure-spectrum correlations, has become possible in addition to the conventional application, the identification of unknown substances on the basis of spectral search in the library. This paper deals with the νOH bands of alcohols, also including diols and diol monoether type compounds, investigating correlations between chemical structure and the features of spectra. For monoalcohols, the frequencies measured in dilute solution and vapour phase, respectively, are correlated; the former were taken from literature, the latter from the vapour phase spectrum library of EPA. For the other types of compound, vapour phase νOH frequencies of free and hydrogen bonded hydroxy groups were studied, and the differences correlated with the hydrogen bonded structures.Peak maxima were determined by a peak picking program; in the case of overlapping bands Fourier self-deconvolution was applied prior to peak picking. For more seriously overlapping bands least-squares curve fitting was applied. In studying correlations, a cluster analysis method (KMEANS) was also used.