Hydroxyl group infrared absorption

Infrared The broad band at 3500 cm 1 indicates a hydroxyl group. The absorptions at 1500 cm 1 and 1600 cm 1 are due to an aromatic ring. The absorption at 830 cm-1 shows that the ring is p-disubstituted. Compound A is probably a phenol. 

The percent absorption or transmission of infrared radiation by a material provides a fingerprint of the material that is useful in determining the exact nature of the compound. Absorptions at specific wavelengths in the near infrared are indicative of various groups within a molecule such as amino, carboxyl, keto, or hydroxyl groups, while absorption in the far infrared is indicative of the nature of the molecule as a whole. The spectrum obtained may also be compared with spectra of known compounds as recorded in the literature. A standard test method for IR analysis is ASTM El252. °... 

During the reaction, protons are extracted from the brucite lattice. Infrared spectra [24, 25, 31] show that during charge the sharp hydroxyl band at 3644 cm" disappears. This absorption is replaced by a diffuse band at 3450 cm"1. The spectra indicate a hydrogen-bonded structure for ft-NiOOH with no free hydroxyl groups. ft-NiOOH probably has some adsorbed and absorbed water. However, TGA data... 

In addition to the simple chemical methods for following these processes, infrared spectroscopy may also be used. In Fig. 9 is shown the spectrum of silica dried at 200°C before and after reaction with Zr(allyl)4- The characteristic absorption bands of the transition metal-allyl group are clearly displayed, also a significant reduction in the number of hydroxyl groups (3740 cm-1) is also clearly evident. 

Functional groups in the substituent at the carbon atom can take part in the formation of new tautomeric forms, as in 115, [Eq. (92)] (87IZV2118 89IZV946 90IZV1133). Infrared spectra of 121 in solvent contain absorption bands for the hydroxyl groups and the N+—H fragment, the former... 

Repeated methylation of bagasse native lignin with dimethyl sulfate yielded a product with a 29-1 % methoxyl content. Four such methyl-ations did not change this value. However, the infrared spectrum of this derivative still revealed a small absorption band at 3400 cm1. Thus, it appeared that at least one hydroxyl group could not be methylated. Treatment of this methylated product with acetic anhydride and pyridine gave an acetate, which did not exhibit an absorption band at 3400 cm-1. Consequently, a tertiary hydroxyl group, which can be acetylated but not methylated, seems to be present in this lignin. 

In addition to the Ti, hydroxyl groups constitute a second class of surface functional groups on dehydrated samples that can be of importance in catalytic reactions. The presence of a large number of Si-OH groups on the surfaces of all the titanosilicates is apparent from the intense absorption in the 3200-3800 cm-1 region of the infrared spectra. The experimental evidence of surface... 

Note that in all the examples discussed so far, infrared spectroscopy gives its information on the catalyst in an indirect way, via hydroxyl groups on the support, or via the adsorption of probe molecules such as CO and NO. The reason why it is often difficult to measure the metal-oxide or metal-sulfide vibrations of the catalytically active phase in transmission infrared spectroscopy is that the frequencies are well below 1000 cm-1, where measurements are difficult because of absorption by the support. Infrared emission and Raman spectroscopy, discussed later on in this chapter, offer better opportunities in this respect. 

Completeness of the methylation reaction is a prerequisite for successful methylation analysis. It can be directly detected from the disappearance of the infrared absorption of the hydroxyl groups,9 but this is often not possible because of the small amount of sample available. 

Using infrared spectroscopy, Yates (299) proved the existence of hydroxyl groups on anatase as well as on rutile. Both forms still contained some adsorbed molecular water after evacuation at 150°, as evidenced by the bending vibration at 1605 cm b After outgassing at 350°, no free water was detected. There remained two OH stretching absorptions in the case of anatase (at 3715 and 3675 cm ) and one weak band at 3680 cm with rutile. This is indication of the existence of two different types of OH groups on anatase. These results were confirmed by Smith (300). 

Lewis, D.G. Cardde, C.M. (1989) Hydrolysis of Fe(III) solution to hydrous iron oxides. Aust. J. Soil Res. 27 103-115 Lewis, D.G. Farmer,V.C. (1986) Infrared absorption of surface hydroxyl groups and lattice vibrations in lepidocrodte (y-FeOOH) and boehmite (y-Al-OOH). Clay Min. 21 93-100... 

A coordination number of 7 does not seem likely for chromium (III) also, the infrared spectrum indicates that this compound contains uncoordinated hydroxyl groups. The similarity of the visible-ultraviolet absorption spectra of [Cr(HO-A)2] and [Cr(AcO-A)2] (above) is further evidence of the identical character of the donor groups in both compounds, and hence, hydroxyl groups appear to be uncoordinated in the former. We must seek an explanation not involving coordination of the hydroxyl oxygen to chromium (III). 

The infrared spectra of systems containing lactoside could not be analyzed in a similar way because the absorption of the hydroxyl groups of the sugar masked the absorptions of cholesterol at 2.8 microns and of the P-O-C group of lecithin between 8 and 10 microns. 

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