Taking a Look at Spectroscopy and Chemical Tests

The carbonyl stretch in the 1,700 cm region of the infrared spectra of carbonyl compounds is a very obvious feature of the spectrum for these compounds, in this section we look at some other spectral features of carboxylic acids and their derivatives, and also at some chemical tests that can help you determine what you re dealing with. 

You can use the unique spectroscopy of carboxylic acids and derivatives, described in the following list, to help you identify those compounds. 

1/ Carboxylic acids In addition to the carbonyl stretch, the infrared 

Amides The carbonyl stretch of amides is in the 1,690-1,630 cm region. If one hydrogen atom is attached to the nitrogen atom, the cimide has an N-H stretch. If two hydrogen atoms are attached to the nitrogen, it has two N-H stretches. The N-H stretches are in the 3,500-3,300 cm region. 

Other derivatives have similar spectral properties. For example, acid anhydrides are similar to esters. 

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