Carboxylic acids infrared spectra, 561 table

Different types of carbonyl groups give characteristic strong absorptions at different positions in the infrared spectrum. As a result, infrared spectroscopy is often the best method to detect and differentiate these carboxylic acid derivatives. Table 21-3 summarizes the characteristic IR absorptions of carbonyl functional groups. As in Chapter 12, we are using about 1710 cm-1 for simple ketones and acids as a standard for comparison. Appendix 2 gives a more complete table of characteristic IR frequencies. 

The major baninfrared spectrum of carboxylic acids (which contain the COOH group) are summarised in Table 4.3h. ... 

In the infrared spectrum, the C=N stretching vibration appears at about 2250 cm in the same range as the C=C absorption, but much more intense. The NMR spectra of nitriles indicate that protons near the nitrile group are deshielded about as much as those in other carboxylic acid and alkyne derivatives (Table 20-3). 

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