Absorption in the infrared

Methylindole has also been prepared by lithium aluminum hydride reduction of 1-methylindoxyl. Compounds giving rise to NH absorption in the infrared (indole, skatole) can be completely removed by refluxing the crude 1-methylindole over sodium for 2 days and then distilling the unreacted 1-methylindole from the sodio derivatives and tarry decomposition products. 

The saturated amine (88) was separated from the enamine (87) by basic hydrolysis, which resulted in the hydrolysis of the enamine. The perchlorate salt of the enamine (89) showed a strong absorption in the infrared at 1680 (characteristic of... 

Figure 8.30. Theoretical energy flux for radiation from the sun as a black body at 5,800 K. The spectrum reaching the surface of the earth is modified through absorption in the infrared region by H2O and CO2 and in the...

The specific requirement for a vibration to give rise to an absorption in the infrared spectrum is that there should be a change in the dipole moment as that vibration occurs. In practice, this means that vibrations which are not centrosymmetric are the ones of interest, and since the symmetry properties of a molecule in the solid state may be different from those of the same molecule in solution, the presence of bands may depend on the physical state of the specimen. This may be an important phenomenon in applying infrared spectroscopy to the study of AB cements. 

B. M. Lichstein, and D. D. Perry The Chemistry of Alane, I. Some Observations on the Effect of the Coordinating Base on the Aluminium-Hydrogen Absorption in the Infrared. Inorg. Chem. 2, 650 (1963). 

The various combustion methods differ primarily in the method of measuring the carbon dioxide generated from the organic carbon. The first really sensitive carbon dioxide detector and the one still most used is the non-dispersive infrared gas analyser. The detecting element senses the difference in absorption of infrared energy between a standard cell filled with a gas with no absorption in the infrared, and a sample cell. Water vapour is the only serious interference, hence the carbon dioxide must be dried before any measurements are made. 

The application of Fourier-transform infrared spectroscopy of polymers has been reviewed. Since the requirements for activity of a vibration for causing absorption in the infrared and for causing... 

Epoxy-dlol Adduct. The epoxy-diol adducts were prepared using standard techniques ( 1 ) by heating a mixture of two moles of diol with one mole of epoxy resin at 130-140°C for 8 hours using 1% N,N-dimethylethanolamine as catalyst. Epoxy-diol adducts prepared in this manner showed the absence of epoxy absorption in the infrared spectrum. 

IR spectra and the isotcpic shifts for the isotopomers greatly aided in the assignment of the absorptions in the infrared spectrum of 4. 

Figure 14.35, for example, shows the real (n) and imaginary (k) parts of the index of refraction (17 = n — ki) of three samples of dust collected in the Barbados, but thought to be transported from the Sahara Desert (Volz, 1973), from Afghanistan (Sokolik et al., 1993), and from Whitehill, Texas, in the southwestern United States (Patterson, 1981), respectively (Sokolik et al., 1998). Regions of absorption in the infrared due to some common dust components are also shown the asymmetric C-O stretch of carbonate in calcite near 7 gm seen in the Texas dust, the asymmetric Si-O-Si... 

The extinction features at energies where water is transparent are rapidly squelched in the ultraviolet as the onset of electronic transitions greatly increases bulk absorption. In the infrared, however, vibrational absorption bands in water are carried over into similar bands in extinction (dominated by absorption if a A) by a water droplet. Unlike MgO there are no appreciable spectral shifts in going from the bulk to particulate states. The reason for this lies in the strength of bulk absorption and will be discussed more thoroughly in Chapter 12. 

Gillis et al. [394g] observed the decay of the solvated electron s optical absorption in the infrared (800—2100 nm) in liquid propane at 88 and... 

The motion of the electrons is treated in the adiabatic approximation. For absorption in the infrared, the electrons remain in the ground state. The electric dipole moment of the complex of two molecules is the expectation value of the dipole moment operator over the ground electronic state, which is a function of the nuclear coordinates only. Specifically, the dipole moment of a complex of n molecules is dependent on the vibrational (r,) and orientational ( ,) coordinates, and on the position (J ,-) of the mass centers of the molecules i, for 1 < i < n,... 

A. Borysow and L. Frommhold. Pressure-induced absorption in the infrared a data base for the modeling of planetary atmospheres. J. geophys. Res., 96 17501, 1991. 

It has bean claimed that there is characteristic oxazirane absorption in the infrared at 6. -7.0 p.11 However, since the carbon-hydrogen bending vibration of alkyl groups appears in this same region, this is a... 

Infrared spectroscopy is not as inherently informative with regard to metal interactions in highly symmetrical metal-metal bound dimers as is Raman spectroscopy, since the totally symmetric metal-metal stretch is a forbidden absorption in the infrared experiment. Oldham and Ketteringham have prepared mixed-halide dimers of the type Re2ClxBr 2xto lower the symmetry and hence introduce some infrared allowedness into the Re-Re stretching mode (206). Indeed, the appearance of a medium-intensity band at 274 cm 1 in the infrared spectrum of the mixed-halo species was considered to be the result of absorption by the metal—metal stretching vibration, which was also observed in the Raman spectrum at 274 cm ". ... 

A new interesting 1,1-dithio ligand was obtained by the addition of KPPh2 to CS2 in tetrahydrofuran (263) or dioxane (396). The KS2CPPh2 salt of the ligand shows strong absorptions in the infrared spectrum at 1000 and 853 cm 1 that have been attributed to the CS2 moiety (263). 

Ozone is endothermic, thus it can burn or detonate by itself and represents the simplest combustible and explosive system, The concentration threshold for spark-initiated explosion ofliquid ozone in oxygen at — 183°C is 18.6 mol % O3 the concentration limit for shock wave-initialed detonation of gaseous ozone-oxygen at 25°C is 9.2 mol % O3. Gaseous ozone exhibits three principal absorptions in the infrared at 710. 1043, and 2105 cm-1... 

Note. (1) The reaction may be monitored by observing the diminution of carbonyl absorption in the infrared spectrum of successive samples withdrawn from the organic phase, after allowing the dichloromethane to evaporate from a portion placed on a sodium chloride plate. Alternatively samples of the reaction medium may be analysed by g.l.c. using a 10 per cent Carbowax column on Chromosorb W held at 150 °C with a nitrogen carrier gas flow rate of 40ml/minute benzaldehyde has tR 2 minutes and phenyloxirane has tR 2.75 minutes. 

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