O—H Bending Vibrations

3 O—H Bending Vibrations The O—H inplane bending vibration occurs in the general region of 1420-1330 cm-1. In primary and secondary alcohols, 

The spectra of alcohols and phenols determined in the liquid state, show a broad absorption band in the 769-650 cm-1 region because of out-of-plane bending of the bonded O—H group. Some spectra showing typical alcoholic absorptions are shown in Appendix B ethyl alcohol (No. 16) and methanol (No. 15). 

FIGURE 2.18. 2-Methyl-l-butanol. O—H stretch, intermolecular hydrogen bonding 3337 cm C—H stretch (see 

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Anhydrous quinazoline hydrochloride absorbs one molecule of water readily, and. the product is difficult to dehydrate completely even in a high vacuum at 60°. Infrared spectral data suggest that this water is covalently bound because of (o) the absence of several bands in the spectrum of the hydrate which are present in the spectrum of the anhydrous hydrochloride and (6) the presence of extra bands at 1474 and 1240 cm that have been attributed to C— H and O— H bending vibrations of the — CHOH group. 

Alcohols and phenols. Both these classes of compounds are characterised by the strong absorption resulting from the O—H stretching modes the position and shape of the bands are sensitive to the electronic and steric features of the compound and also to the physical state of the sample. Absorption bands arising from C—O stretching and O—H bending vibrations are also of diagnostic value. 

The absorption at 1400 cm may be due to the O—H bending vibrations of alcohols or carboxylic acids, as occurs with simple model compounds. 

The FTIR spectra of SDC powders synthesized by the modified Pechini method and calcined at different temperatures are shown in Fig. 8. The peaks at around 3400 and 1640 cm-i correspond to the H-O stretching and H-O-H bending vibration, respectively. They indicate that water or hydroxyl groups still existed not only in the as-prepared, but also in all calcined samples. A low intensity band at 1380 cm-i in the as-prepared powder might indicate the physical adsorption of CO2 or be caused by residual NCX- (Chen et al., 2006). However, this band is eliminated after heat treatment. Therefore, although a synthesis temperature as low as 350 °C was sufficient to produce the SDC phase, powders with higher purity were obtained by calcining above 700 °C. 

Fig. 2.2 Variation of O-H bending vibration frequencies of physically adsorbed water and DMFC maximum power density vs. the pH of slurry of the fillers. The inset shows...

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