Overtone region

Infrared spectral studies of polymeric sulfur are scarce and mainly the overtone region was studied [142, 180]. In the range of the stretching vibrations, two bands at ca. 460 cm (strong) and ca. 423 cm (medium) were reported for Crystex after extraction of the soluble ring fraction by CS2 [180]. The results of the literature are summarized in Table 12. 

L. England Kretzer and W. A. P. Luck, Band analysis of CH3OH and CH3OD H bond complexes in the first overtone region. J. Mol. Struct. 348, 373 376 (1995). 

D 1840-1940 cm Aromatic overtone region Quite clear fingerprint but does not reflect 2 band pattern proposed for p-disubstitution.- ... 

Historically, collision-induced absorption was discovered in the fundamental band of oxygen and nitrogen [128], Fig. 1.1. Literally, any molecular complex may be expected to have more or less prominent induced bands in the fundamental band and overtone regions of the molecules involved-besides the rototranslational bands considered above. Induced vibrational spectra are indeed known for many molecular systems and selected examples will be discussed below. Since in virtually all of these spectra rotation and vibration are coupled, we will generally refer to these as rotovibrational induced spectra. 

A. Watanabe, J. L. Hunt, and H. L. Welsh. Structure of the pressure induced infrared spectrum of hydrogen in the first overtone region. Can. J. Phys., 49 860, 1971. 

The insoluble material is assumed to be the graft copolymer and this is verified by infrared spectroscopy. For grafting onto the butadiene portion of a copolymer, the C-H out-of-plane bending vibrations as well as the olefin C-H stretching vibration are most useful. The graft copolymer of acrylonitrile onto polystyrene cannot be analyzed by infrared spectroscopy since the only change would be in the C-H overtone region and these bands are too weak to permit interpretation. 

Luck, W. A. P. Infrared Overtone Region, in Structure of Water and Aqueous Solutions (ed. W. A. P. Luck), Chapt. III. 3. Weinheim Verlag Chemie 1974. 

Figure 7. IR spectra in the combination/overtone region showing the photochemical reaction of Cr(CO)6 in scC2H4 at ambient temperature. The first spectrum shown in the Figure was recorded just before the UV lamp was switched on, and subsequent spectra were taken at ca. 10 min intervals. The bands labelled are those of Cr(CO)6 and those labelled A show the growth of the final photoproduct Cr(CO)4(C2H4)2. The steady state concentration of the intermediate species Cr(CO)5(C2H4) is relatively low, hence the overtone/combination bands of this species are not observed in this experiment.

The differentiation is easily made by noting the characteristic absorption bands corresponding to the aromatic ring system around 1600-1450cm-1 and 850-660cm-1, and the characteristic pattern in the overtone region around 2000-1800 cm- The origin of these absorptions is discussed in detail below their presence in this spectrum clearly shows that the structure is a mono-substituted aromatic compound. 

In the overtone region of the spectra of HOD in DjO, the intensity of a band at 7062 cm-1 (ca. twice the fundamental stretching frequency for OH), increases as the temperature is raised, superimposed spectra showing isosbestic points (Worley and Klotz, 1966). This band was assigned to free OH groups (see also Luck and... 

Figure 6.2-7 Molar absorption coefficient e of pure CO (density 0.15 g cm 127 °C) in the fundamental as well as the first and second stretching overtone regions.

I, If CO concentrations are to be measured spectroscopically during a chemical process or in chemical equilibrium or phase equilibrium studies, quite different optical path lengths / and thus reactor dimensions may be used. As an example, / is calculated for a system where the CO concentration is 0.15 g cm In order to ensure the good quality of the spectra, the absorbance at the band maxima should not exceed = 1. With this limiting absorbance, the optical path lengths calculated from the values in the band maxima (Fig. 6.2-7) are 0.066 mm, 7.9 mm, and 1120 mm, respectively, in the fundamental, first, and second overtone region. 

Fig. 6.2-18 shows the first and second overtone regions of C- H stretching modes in the near-infrared spectra of three 1-alkynes (CsHg, CeHio, C7H12, from bottom to top). The C-H stretching modes of triply bound C- H groups are shifted to still higher wavenumbers. The first overtone is observed around 6525 cm (Fig. 6.2-18a), and the second overtone is found around 9637 cm (Fig. 6.2-18b). These absorptions are thus distinctly set off from those of C-H groups whose carbon atom is involved in single or double bonds.

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