Infrared band intensities and bond polarities: Part 5 - XCl4 molecules (X = C,Si, Ge,Sn)

Gas phase band intensities of v₃ and v₄ of SiCl₄, GeCl₄ and SnCl₄ have been derived from dispersion curves measured using a Michelson interferometer in the range 1000 to 10 cm^?1. The results obtained are discussed in relation to the corresponding liquid phase band intensities. Bond polar properties are derived from the observed intensities using a modified Gribov method, the moments obtained being 0.9 D for SiCl, 1.5 D for GeCl and 2.7 D for SnCl.     

Vibrational spectra and torsional analyses of cis-2,3-dimethyloxirane and trans-2,3-dimethyloxirane

The Raman spectra of cis-2,3-dimethyloxirane and trans-2,3-dimethyloxirane in the vapor, liquid, and polycrystalline solid phases are reported for the region between 25 and 3100 cm^?1. The IR spectra of these two compounds between 80 and 4000 cm^?1 in the vapor and polycrystalline solid phases are also reported. In the IR and Raman spectra of gaseous trans-2,3-dimethyloxirane a total of eight torsional transitions have been observed. In the Raman spectrum of the cis compound in the vapor phase, four torsional transitions have been observed. From these experimental data, periodic barriers to the methyl torsional motions have been calculated to be 905 ± 7 cm^?1 (2.5 kcal mol^?1) for the trans molecule and 617 ±5 cm^?1 (1.76 kcal mol^?1) for the cis molecule. Additionally, complete vibrational assignments based on band contours, depolarization values, and group frequencies are proposed for both molecules and gas-phase thermodynamic functions have been calculated. These results are compared to the corresponding quantities for some similar molecules.     

The vibrational analysis and torsional study of trans-1,2-dimethylcyclopropane and cis-1,2-dimethylcyclopropane

The infrared spectra of cis-1,2-dimethylcyclopropane and trans-1,2-dimethylcyclopropane have been recorded between 4000 and 200 cm^?1 in the polycrystalline solid phase, and 4000 to 80 cm^?1 in the gas phase. The Raman spectra of these two compounds in the gaseous and liquid phases were also recorded between 3100 and 10 cm^?1. An assignment of the thirty-nine fundamental vibrations for both cis- and trans-1,2-dimethylcyclopropane is proposed, and comparisons are made with the vibrations of other similar molecules. Additionally, ten torsional transitions were observed in the far infrared and Raman spectra of cis-1,2-dimethylcyclopropane, and four transitions were observed in the spectra of the trans compound. From these spectral data, torsional barriers were determined. The effective barriers to methyl torsion are 2.92 kcal mol^?1 (12.20 kJ mol^?1) for cis-1,2-dimethylcyclopropane and 2.61 kcal mol^?1 (11.14 kJ mol^?1) for trans-1,2-dimethylcyclopronane.     

The infrared spectra and conformation of methyl and ethyl propenyl ethers

The infrared spectra of the cis and trans geometric isomers of methyl and ethyl propenyl ethers have been recorded in the liquid and vapour phase, in the region 4000-200 cm^?1. Solid phase spectra have also been recorded for all but trans methyl propenyl ether. Evidence is given for the existence of two rotameric forms for both the trans compounds, in each case the more stable conformer being planar s-cis; but a single non-planar conformation is suggested for the two cis isomers. The enthalpy difference between the two rotameric forms in trans ethyl propenyl ether was found to be 4.6 ± 1.0 kJ mol^?1 (1100 ± 250 cal mol^?1).     

Thermally induced phase separation of poly(vinylidene fluoride)/diluent systems: Optical microscope and infrared spectroscopy studies

Thermally induced phase separation (TIPS) has been developed to prepare porous membranes. The porous structures are mainly dependent on diluents adopted in the TIPS process. We obtained two typical morphologies of poly(vinylidene fluoride) (PVDF) membranes using cyclohexanone (CO) and propylene carbonate (PC) as diluents, respectively. SEM observation displays that porous spherulites are formed from PVDF/CO system, whereas smooth particles result from PVDF/PC system. The TIPS processes of these two systems have been investigated in detail by optical microscope observation and temperature‐dependent FTIR combined with two‐dimensional infrared correlation analysis. Rapid crystallization of PVDF can be seen around 110 °C in the PVDF/CO system, which is consistent with the results of temperature‐dependent FTIR spectra. The spectral evolution indicates a transform of PVDF from amorphous to α‐phase after 110 °C. The ν_s(C?O) band at 1712 cm^?1 narrows and the ν_s(C? F) band at 1188 cm^?1 shifts to 1192 cm^?1 before crystallization, which implies the destruction of interaction between PVDF and CO. In contrast, the PVDF/PC system shows slow crystallization with all‐trans conformation assigned to β‐phase and γ‐phase below 60 °C but no obvious change of polymer?diluent interaction. We propose two mechanisms for the different phase behaviors of PVDF/CO and PVDF/PC systems: a solid?liquid phase separation after destruction of polymer?diluent interaction in the former, and a liquid?liquid phase separation process coupled with rich‐phase crystallization in the later. This work may provide new insight into the relationship among morphologies, crystal forms, and phase separation processes, which will be helpful to adjust membrane structure. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1438–1447     

Vibrational spectrum and conformation of cyclopropyldichloroborane

The infrared (3500-40 cm^?1) and Raman spectra (3200-0 cm^?1) have been recorded for cyclopropyldichloroborane in both the gaseous and solid states. Additionally, the Raman spectrum of the liquid was recorded and qualitative depolarization values obtained. Only one conformation has been found in all three physical states and, on the basis of the polarized nature of the Raman band assigned as the BCl₂ antisymmetric stretch, this conformer has been identified as being the bisected structure with C_s molecular symmetry. A complete vibrational assignment is proposed based on Raman depolarization data, infrared gas phase band contours, and group frequencies. These results are compared with the corresponding data in other organoboranes.     

Spectra and structure of small ring compounds: Part XXXV. Vibrational spectra and ring-puckering and torsional potential functions of cyclobutylamine

The IR spectra (50–4000 cm^?1) of gaseous and solid cyclobutylamine and cyclobutylamine-N-d₂ and the Raman spectra (25–4000 cm^?1) of gaseous, liquid and solid cyclobutylamine and cyclobutylamine-N-d₂ have been recorded. Depolarization values were measured for both the gaseous and liquid states. Most of the thirty-six fundamental vibrations have been assigned and support for more than one molecular configuration is presented. In the low frequency region for the “light” compound, a series of four Q-branches have been assigned to transitions between energy levels of the ring-puckering vibration for the equatorial isomer. The transitional frequencies were fitted to an asymmetric single-minimum potential function of the form: V(X) = 0.474 × 10⁶X⁴ - 0.204 × 10⁵X² + 0.993 × 10⁵X³ with a reduced mass of 160 amu. The following torsional potential constants were determined for the “light” molecule- V¹ = 77.8 ± 17.0 cm^?1, V₃ = 784.0 ± 3.3 cm^?1. The trans conformation was found to be more stable than the gauche form by approximately 58 cm^?1 (0.17 kcal mol^?1). The barriers to trans-gauche, gauche-trans, and gauche-gauche interconversion are 803, 745 and 803 cm^?1, respectively.     

Novel Cyclic Sulfonium‐Based Ionic Liquids: Synthesis,Characterization, and Physicochemical Properties

A new series of ionic liquids composed of three cyclic sulfonium cations and four anions has been synthesized and characterized. Their physicochemical properties, including their spectroscopic characteristics, ion cluster behavior, surface properties, phase transitions, thermal stability, density, viscosity, refractive index, tribological properties, ion conductivity, and electrochemical window have been comprehensively studied. Eight of these salts are liquids at room temperature, at which some salts based on [NO₃]^? and [NTf₂]^? ions exhibit organic plastic crystal behaviors, and all the saccharin‐based salts display relatively high refractive indices (1.442–1.594). In addition, some ionic liquids with the [NTf₂]^? ion exhibit peculiar spectroscopic characteristics in FTIR and UV/Vis regions, whilst those salts based on the [DCA]^? ion show lower viscosities (34.2–62.6 mPa s at 20 °C) and much higher conductivities (7.6–17.6 mS cm^?1 at 20 °C) than most traditional 1,3‐dialkylimidazolium salts.     

Solvent extraction and spectrophotometric determination of titanium(IV) with 3-phenyl-3-methyl-2-mercaptopropenoic acid

The distribution equilibria of 3-phenyl-3-methyl-2-mercaptopropenoic acid (PhMMP) and the titanium(IV)-PhMMP complex have been studied. An extraction-photometric method for the determination of microamounts of titanium has been developed. We have investigated the influence of pH, the reagent, and the presence of electrolytes and masking agents in the aqueous phase on the equilibrium. From the slope analysis of the distribution curves the composition of the extracted species has been found to be Ti(OH)₂(HR)₂. The complex is extracted quantitatively. Beer's Law is followed over the range 0.09–3.74 μg ml^?1 of titanium(IV), the molar absorptivity is 1.65 × 10⁴ liters mol^?1 cm^?1, and the Sandell sensitivity is 2.8 ng cm^?2 at 439 nm. This method has been applied to the determination of titanium in a bauxite.     

Spectra and structure of organophosphorus compounds: XVII. Infrared and Raman spectra. vibrational assignment and barriers to internal rotation for t-butylphosphine

The infrared spectra of gaseous and solid tertiary-butylphosphine, [(CH₃)₃CPH₂], have been recorded from 50 cm^?1 to 3500 cm^?1. The Raman spectra of gaseous, liquid and solid (CH₃)₃CPH₂ have been recorded from 10 to 3500 cm^?1. A vibrational assignment of the 42 normal modes has been made. A harmonic approximation of the methyl torsional barrier from observed transitions in the solid state gave a result of 4.22 kcal mol^?1 and 3.81 kcal mol^?1 in the gaseous state. Hot band transitions for the phosphino torsional mode have been observed. The potential function for internal rotation about the C-P bond has been calculated. The two potential constants were determined to be: V₃ = 2.79 ± 0.01 kcal mol^?1 and V₆ = 0.07 ± 0.01 kcal mol^?1.     

Temperature-dependent vibrational spectroscopic studies of pure and gold nanoparticles dispersed 4-n-Hexyloxy-4’-cyanobiphenyls

Raman spectra of pure and 2 wt.% gold nanoparticles (GNPs) dispersed liquid crystalline compound 4-n-Hexyloxy-4?- cyanobiphenyls (6OCB) has been recorded as a function of temperature from room temperature (solid crystal) to 80°C (isotropic liquid) in the spectral region of 500–2500 cm^?1. The variation of Raman spectral parameters (peak positions and line width) with temperature is used to explain the changes in molecular alignment and its effect on inter-/intra-molecular interactions at crystal-Nematic (K-N) transition. To understand the change in molecular structure during phase transition and on account of dispersion of gold nanoparticles in pure liquid crystal more precisely, two spectral regions 1000–1500 cm^?1 and 1500–2400 cm^?1 have been selected separately. From the detailed study, it is concluded that increased orientational/vibrational freedom of the molecules as well as delocalisation of electron clouds results in the spectral anomalies at K-N transition. The geometrical structure of 6OCB was optimised using density functional theory (DFT) and theoretical Raman spectra have been obtained for comparison with experimental spectra. The tentative assignment of vibrational modes observed in our region of study was calculated based on potential energy distribution (PED) using vibrational energy distribution analysis (VEDA) calculation.     

Infrared,Raman spectra and vibrational assignment of (PF2)2O

The IR spectra of gaseous and solid (PF₂)₂O has been recorded from 80 to 1200 cm^?1. The Raman spectra of gaseous, liquid and solid (PF₂)₂O have also been obtained (30–1000 cm^?1). The spectra of the fluid phases indicate the presence of at least two conformers. The spectrum of the solid phase can readily be interpreted on the basis of a single conformer possessing a symmetry lower than C_2v. A vibrational assignment is proposed for all normal modes except the PF₂ torsions. The results are compared with similar data of related compounds. There appear to be two molecules per primitive cell based upon the low-frequency Raman data.     

The vibrational spectra,rotational isomerism,normal coordinate analysis and mean amplitudes of ethyl formate,ethyl chloroformate and ethyl cyanoform

The infrared spectra of ethyl formate, chloroformate, and cyanoformate in the liquid phase have been recorded in the region 4000–4020 cm^?1, and in the solid and vapour phase and in solution in the region 4000–4200 cm^?1. Evidence is reported for the existence of two rotameric forms in each case.Normal coordinate calculations are reported for both rotameric forms of the first two esters, and assignments based on potential energy distributions are given. These assignments show considerable mixing of the normal modes and suggest the inadequacy of simple assignments made by comparison with related molecules.Calculated mean amplitudes are also reported for the first two molecules.     

Conformational analysis,barriers to internal rotation and vibrational assignment for dimethylethylamine

The IR (50–3500 cm^?1) and Raman (20–3500 cm^?1) spectra have been recorded for gaseous and solid dimethylethylamine. Additionally, the Raman spectrum of the liquid has been recorded and qualitative depolarization values have been obtained. Due to the fact that three distinct Raman lines disappear on going from the fluid phases to the solid state, it is concluded that the molecule exists as a mixture of the gauche and trans conformers in the fluid phases with the gauche conformer being more stable and the only one present in the spectra of the unannealed solid. From the temperature study of the Raman spectrum of the liquid a rough estimate of 3.9 kcal mol^?1 has been obtained for ΔH. Relying mainly on group frequencies and relative intensities of the IR and Raman lines, a complete vibrational assignment is proposed for the gauche conformer. The potential functions for the three methyl rotors have been obtained, and the barriers to internal rotation for the two CH₃ rotors attached to the nitrogen atom have been calculated to be 3.51 and 3.43 kcal mol^?1, whereas the barrier for the CH₃ rotor of the ethyl group has been calculated to be 3.71 kcal mol^?1. The asymmetric torsional mode for the gauche conformer has been observed in both the IR and Raman spectra of the gas at 105 cm^?1 with at least one hot band at a lower frequency. Since the corresponding mode has not been observed for the trans conformer, it is not possible to obtain the potential function for the asymmetric rotation although estimates on the magnitudes of some of the terms have been made. Significant changes occur in the low-frequency IR and Raman spectra of the solid with repeated annealing; several possible reasons for these changes are discussed and one possible explanation is that a conformational change is taking place in the solid where the trans form is stabilized by crystal packing forces. These results are compared to the corresponding quantities for some similar amines.     

Optical constants and vibrational assignment of liquid toluene-d8 between 4000 and 450 cm at 25 °C

The optical constants (real and imaginary refractive indices) and imaginary molar polarizability spectrum of liquid toluene-d₈ are presented for the first time. The spectra were determined between 4000 and 450 cm⁻¹ at 25 °C. The fundamentals of toluene-d₈ in the liquid phase are revisited with the aid of gas phase spectra of toluene and toluene-d₈, ab initio calculations, and previously reported liquid assignments of toluene.     

Raman spectra of gases: XIV. Hexachlorodisiloxane

The Raman spectra (50–1200 cm^?1) of gaseous, liquid, and solid (Cl₃Si)₂O have been recorded. The infrared spectra of the gas and solid have been recorded from 55–2000 cm^?1 . The spectra of the gas have been interpreted in detail on the basis of C_2v symmetry with the A₁ skeletal Si-O-Si bend assigned at 63 cm^?1. The spectra gave evidence that there are structural changes upon condensation of the gas and the Si-O-Si angle approaches linearity in the solid state. The opening of this angle is probably due to crystal packing factors.     

Glyoxal oligomers: A computational study

Ab initio calculations at MP2/6‐311++G(2d,2p) computational level was used to analyze interactions between glyoxal (OCHCHO) dimers and trimers in the gas phase. The structures obtained have been analyzed with the atoms in molecules and natural bond orbital methodologies. Eight minima were located on the potential energy surface of the dimers. Eighteen different structures have been obtained for the trimers. CH···O type of interactions is clustering OCHCHO molecules in studied oligomers. Stabilization energies of dimers and trimers including basis set superposition error and ZPE corrections are in the range 4–8 kJ mol^?1 and 12–19 kJ mol^?1, respectively. Blue shift of CH bond upon complex formation in the ranges between 30–45 and 30–55 cm^?1 was predicted for dimers and trimers, respectively. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Automated hollow‐fiber liquid‐phase microextraction followed by liquid chromatography with mass spectrometry for the determination of benzodiazepine drugs in biological samples

In this study, two‐phase hollow‐fiber liquid‐phase microextraction and three‐phase hollow‐fiber liquid‐phase microextraction based on two immiscible organic solvents were compared for extraction of oxazepam and Lorazepam. Separations were performed on a liquid chromatography with mass spectrometry instrument. Under optimal conditions, three‐phase hollow‐fiber liquid‐phase microextraction based on two immiscible organic solvents has a better extraction efficiency. In a urine sample, for three‐phase hollow fiber liquid‐phase microextraction based on two immiscible organic solvents, the calibration curves were found to be linear in the range of 0.6–200 and 0.9–200 μg L^?1 and the limits of detection were 0.2 and 0.3 μg L^?1 for oxazepam and lorazepam, respectively. For two‐phase hollow fiber liquid‐phase microextraction, the calibration curves were found to be linear in the range of 1–200 and 1.5–200 μg L^?1 and the limits of detection were 0.3 and 0.5 μg L^?1 for oxazepam and lorazepam, respectively. In a urine sample, for three‐phase hollow‐fiber‐based liquid‐phase microextraction based on two immiscible organic solvents, relative standard deviations in the range of 4.2–4.5% and preconcentration factors in the range of 70–180 were obtained for oxazepam and lorazepam, respectively. Also for the two‐phase hollow‐fiber liquid‐phase microextraction, preconcentration factors in the range of 101–257 were obtained for oxazepam and lorazepam, respectively.     

Infrared spectrum of D2O vibrationally decoupled in H2O ice Ic

The study of D₂O isolated in amorphous H₂O (ice Iv) has been extended to the determination of the bending mode frequency (1230 cm^?1) and to the measurement of the vibrational spectrum of the cubic ice phase (ice Ic). The vibrationally decoupled stretching frequencies (ν₁ = 2367 cm^?1 and ν₃ = 2444 cm^?1) for D₂O in the H₂O (Ic) have been obtained and an estimate of the exchange activation energy is given.