Gas phase infrared

Vreugdenhil A J and Butler I S 1998 Investigation of MMT adsorption on soils by diffuse reflectance infrared spectroscopy DRIFTS and headspace analysis gas-phase infrared spectroscopy HAGIS Appl. Organomet. Chem. 

Whether the molecule is a prolate or an oblate asymmetric rotor, type A, B or C selection mles result in characteristic band shapes. These shapes, or contours, are particularly important in gas-phase infrared spectra of large asymmetric rotors, whose rotational lines are not resolved, for assigning symmetry species to observed fundamentals. 

The infrared spectrum of matrix-trapped CF2 (produced by the photolysis of difluorodiazirine, CF2N2) has been examined 28 The three fundamental vibrational frequencies were determined to be 668,1102, and 1222 cm. The intensities of the two stretching fundamentals were sufficiently strong to permit observation of the corresponding absorption of13CF2, from which the bond angle of CF2 was calculated to be approximately 108 °. The gas-phase infrared... 

The CH cation 1, protonated methane, is the parent of hypercoordinated carbocations containing a five coordinated carbon atom. It is elusive in solution and has not been observed by NMR spectroscopy but gas-phase infrared investigations have shown its fluxional structure which has been proven by ab initio molecular dynamic simulation.18... 

T. D. Frigden, L. MacAleese, T. B. McMahon, J. Lemaire, and P. Maitre, Gas phase infrared multiple photon dissociation spectra of methanol, ethanol and propanol proton bound dimers, protonated propanol and the propanol/water proton bound dimer. Phys. Chem. Chem. Phys. 8, 955 966 (2006). 

As already pointed out, it is possible to monitor the purity of the fractions by methods such as vapor pressure (see below) or gas phase infrared spectroscopy (Chapter 9). In planning an experiment, solvents and reactants are often chosen such that their vapor pressures facilitate the separation of reactants, products, and solvent. For compounds of similar volatility, more advanced separation techniques are required, such as fractional codistillation, low temperature column distillation, or gas chromatography, all of which are described in Chapter 9. 

I. Spectroscopic Determinations. Gas-phase infrared spectra provide a useful adjunct to vapor pressure measurements in the identification of volatile materials. The cell illustrated in Fig. 9.15 allows the sample to be quantitatively returned to the vacuum line after the spectrum has been obtained, so the process is completely nondestructive. The primary problem with a gas cell is to obtain a vacuum-tight seal between the window material and the cell body this may be accomplished with Glyptal paint or with wax- If the latter is used, it is necessary to warm and cool the alkali halide windows slowly to avoid cracking them due to thermal stress. For this purpose an infrared lamp is handy. The most satisfactory method of attaching windows is O-rings because this allows the easy removal of the windows for cleaning and polishing. 

The contaminants in commercial boron trichloride usually are HCI and COCI2, as well as oxychlorides which have some volatility. The oxyhalides are readily removed by one or two trap-to-trap distillations in a clean vacuum system. Most of the HCl can be removed by holding the BCI3 at — 78°C and pumping away the volatiles for a brief period (some BCI3 is sacrificed in the process). Phosgene, which may be detected by its gas-phase infrared absorption at 850 cm"1, is very difficult to remove. Liquid boron tribromide is generally supplied in sealed ampules. If it is straw colored, dibromine is a likely impurity, and this... 

Fig. 9.15. A gas-phase infrared cell. Note that a thin gasket is included between the metal retaining plate and the window. This helps to reduce window breakage owing to uneven tightening of the nuts.

With the exception that — 80°C. traps (Dry Ice-acetone) are used instead of the — 126°C. traps, this synthesis is accomplished as detailed above in Sec. C. From 14.9 g. (0.075 mole) of trimethyltin chloride and 10.0 g. (0.26 mole) of sodium boro-hydride, an 11.4-g. (0.069-mole, 92%) sample of a colorless liquid product was obtained. The product was identified as trimethyltin hydride from its gas-phase infrared spectrum 14 from its boiling point, 58°C./752 mm., literature,2 59°C./760 mm. and from its refractive index, n 1.4472, literature,2 1.4484. 

Initially, ground-state geometry and vibrational frequencies were reported erroneously 7 . However, electronic, microwave, gas-phase infrared and matrix infrared spectra reported more recently turned out to be consistent with the ground-state parameters listed in Table 18. i>, and v3 at 850 cm-1 are perturbed by their close proximity and overlap, but the assignment has been supported by the observation of 29Si and 30Si isotopic shifts. v2 has been observed directly ° and been obtained from the microwave spectrum for the v=0 and v=l levels of v2. Furthermore the electronic transitions 4, - 1BI and 3fi, - lA3 exhibit a moderately pronounced progression with v2 = 343 cm-181-83 ... 

The vapor pressure of /i-[(CH3)2N]B2H5 obeys the relationship log P = 2158.56/T + 1.75 log T - 0.008061T + 7.518831 (101 torr at 0°). The gas-phase infrared spectrum has been reported in detail.5 The compound is a useful intermediate in the synthesis of other boron nitrogen compounds, including those containing NBNB6 and PBNB7 chains, and Na[(CH3)2-N(BH3)2].8 The compound can be stored at 25° for months in sealed, evacuated Pyrex tubes. It is soluble in ethers and aromatic hydrocarbons, but is attacked by protic solvents. 

Quantities concerned with spectral absorption intensity and relations among these quantities are discussed in references [59]—[61], and a list of published measurements of line intensities and band intensities for gas phase infrared spectra may be found in references [60] and [61]. 

Mons, M. Dimicoli, I. Piuzzi, F. Tardivel, B. Elhanine, M. Tautomerism of the DNA base guanine and its methylated daivatives as studied by gas-phase infrared and ultraviolet spectroscopy, J. Phys. Chem. A 2002,106, 5088-5094. 

Besides the above-mentioned application for volatile, stable compounds, the technique of matrix isolation is superior to gas-phase investigation of compounds with a low vapor pressure. The vapor pressure of molybdenum hexacarbonyl, Mo(CO)6, for instance, is only 10 mbar at room temperature, which is insufficient for ordinary gas-phase infrared measurements. However, if Mo(CO)6 is flushed with a stream of matrix gas and if the final mixture is deposited as a matrix, then the density of the Mo(CO)6 molecules increases considerably. This integration effect (the deposition time varies from 5 minutes to several hours) is very important for high-temperature species and has interesting analytical applications. 

High-resolution gas-phase infrared (IR) spectroscopy was employed in rovibrational analysis of the Vi band of diazirine-42 (D2CN2) <2001JSP(205)86>, with the aim of providing accurate data for comparison with state-of-the-art quantum-chemical ab initio calculations. The V2 vibrational mode can be approximated to N=N stretching at a resolution of 0.005 cm this was widely perturbed. A pentad model was employed to take into account the possible perturbers. 

Kawaguchi, K, Gas-phase infrared spectroscopy of ClHCl, J. Chem. Phys. 88, 4186-4189 (1988). 

Lemaire J, Boissel P, Heninger M, Mauclaire GB, G, Mestdagh H, Simon A, Le Caer S, Ortega JM, Glotin F, Maitre P. (2002) Gas phase infrared spectroscopy of selectively prepared ions. Phys Rev Lett 89 273002/1-273002/4. 

The thermal decomposition studies were initially carried out by following weight-loss as functions of time and temperature of the sample when under vacuum. When the lowest temperature for rapid weight-loss had been established it was our practice to hold the sample at this temperature until constant weight was attained. The volatiles were trapped at -196° and were subsequently examined by gas-phase Infrared spectroscopy. The residual solids in the Monel tubes were examined by X-ray powder photography, Raman and Infrared spectroscopy and were also tested for para- or diamagnetism. 

Buchler and Harran (5) observed only two vibrational frequencies, 1935 and 600 cm . In their gas-phase infrared spectra. These two frequencies are In reasonable agreement with those reported by Seshadrl (4). 

Vibrational frequencies are from gas-phase infrared spectra (9) measured with a grating spectrometer by Buerger et al. 

Vibrational frequencies are those selected by Shiraanouchl ( ) based on gas-phase infrared spectra (9) and liquid-phase Raman spectra (1 ). Gas-phase frequencies are adopted except for = 122 cm and infrared inactive Vg 688 cm... 

The fundamental vibrations are those observed in the gas-phase Raman spectra by Monostorl and Weber ( ) and the gas-phase infrared spectra by Makl et al. (6) and Chalmers and McKean (7 ). The frequencies are essentially the same as those selected by Shimanouchi (8) who also lists earlier spectral studies. Electron-diffraction studies of the gas were reported by Thornton (9) and Hoffman and Livingston ( 0). The adopted bond length is the average of these two results which differ by only 0.006 A. 

The vibrational frequencies are rounded values taken from the gas phase infrared and liquid phase Raman study of Griffiths ( ). The infrared data are supported by results obtained in an earlier study ( ). Griffiths (4) assigned the Raman band at... 

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