Infrared band shifts

Unfortunately microcalorimetry experiments for the heat of wetting are difficult to perform due to the care that must be taken to keep the powder surface free from adsorbed impvuities. As a result an approximate method based on an infrared band shift caused by the interaction of the solvent with the solid surface has been developed. Drago often used spectroscopic shifts,, of the OH stretching frequency of phe-... 

Plutonium(IV) polymer has been examined by infrared spectroscopy (26). One of the prominent features in the infrared spectrum of the polymer is an intense band in the OH stretching region at 3400 cm 1. Upon deuteration, this band shifts to 2400 cm 1. However, it could not be positively assigned to OH vibrations in the polymer due to absorption of water by the KBr pellet. In view of the broad band observed in this same region for I, it now seems likely that the bands observed previously for Pu(IV) polymer are actually due to OH in the polymer. Indeed, we have observed a similar shift in the sharp absorption of U(0H)2S0ir upon deuteration (28). This absorption shifts from 3500 cm 1 to 2600 cm 1. 

Far-Infrared Bands and Shifts of the vC=C Stretching and SC-H o.p. Bending Vibrations of Benzene upon Complexation (171)... 

Figure 5 shows a series of infrared spectra taken during the TPR of NO with CH4. At temperatures less than 350 °C the spectra in Figure 5 are virtually identical to those for NO TPR seen in Figure 4. Above 350 °C the nitrosyl bands are more intense in the presence of CH4. A new peak appears at 2270 cm when the temperature is raised to 400 °C and above, and another one appears at 2173 cm at 450 °C. Neither of these bands was observed when the reaction mixture was passed over Na-ZSM-5. When 5NO was substituted for NO, the two bands appeared at 2256 cm- and 2144 cm, and when 3CH4 was substituted for 12CH4, the bands shifted to 2237 cm and 2132 cm-. Based on previous studies [32-34], the band at 2270 cm- is best attributed to NCO species adsorbed at Al + sites. The observed shift in the...

Fig. 9. (a) Infrared spectra of outgassed thin pellets of Ti-free silicalite (curve 1) and TS-1 with increasing Ti content x (curves 2-5). Spectra were normalized by means of the overtone bands between 1500 and 2000 cm-1 (not shown) and vertically shifted for clarity. The thick horizontal line represents the fwhm of the 960 cm-1 band for sample 2. By assuming that this band has a constant fwhm for any x, the absorbance W obtained is plotted as the ordinate in panel b, where the band has the same fwhm as in curve 2 (horizontal thin lines), (b) Intensity W of the 960 cm-1 infrared band (normalized absorbance units) as a function of x (full squares) and corresponding Raman counts (open squares) [Reprinted from Ricchiardi et al. (41) with permission. Copyright (2001) American Chemical Society]. 

Large bandwidth, red-shifted infrared band corresponding to hydrogen bonded OH groups at 3400 cm. ... 

The infrared spectrum of the Niy-S state indicates even a slight decrease of charge density on Fe (a shift of the CN/CO bands to higher frequencies). In the infrared spectrum of the Nir-S state, however, all bands have shifted to considerably lower frequencies (the CO band shifts 43 cm ), indicating a greatly increased charge density on Fe. Two possible ways to explain this are e.g ... 

Busca (18b) has evaluated the literature values for infrared bands attributed to coordinated and adsorbed dioxygen species. He concludes that it is very difficult to deduce the nature of the dioxygen coordination from measurements of the frequency shift, Av00, with respect to the stretching frequency of the free molecule. It needs to be stressed that it is also difficult to distinguish between mononuclear and molecular species from measurements of v00, and this can only be achieved by careful interpretation of experiments using 160/180 isotopic mixtures. The absence of such experiments very often accounts for the conflicting attributions in the literature which are discussed in later sections. 

C-H infrared band in the phenanthrene soluble fraction relative to the original coal and also a shift in the position of the bands.. These observations agree with the postulated mechanism. 

Exercise 14-1 Deduce the structures of the two compounds whose nmr and infrared spectra are shown in Figure 14-1 (p. 540). Assign as many of the infrared bands as you can and analyze the nmr spectra in terms of chemical shifts and spin-spin splittings. 

The infrared band of a particular group in a polymer shifts when some groups of the polymer are adsorbed onto active sites, e.g. silanol groups on a silica surface23. This phenomenon has been used to measure the fraction of adsorbed polymer segments. The fraction of die surface sites occupied by adsorbed polymer segments can also be determined from the frequency shift of 1R band caused by the interaction between functional groups and an active site. 

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