Nitriles infrared absorption frequencies

The P-Khb values of some nitriles are mentioned in Table 16. The infrared spectra show only one symmetrical v(OH ) absorption and high-frequency shifts of the v(C=N)... 

Nitriles Nitriles show a characteristic C = N stretching absorption around 2200 cm-1 in the infrared spectrum. This absorption can be distinguished from the alkyne C=C absorption by two characteristics Nitriles usually absorb at frequencies slightly higher than 2200 cm-1 (to the left of 2200 cm-1), while alkynes usually absorb at frequencies slightly lower than 2200 cm-1 and nitrile absorptions are usually stronger because the C = N triple bond is more polar than the alkyne C=C triple bond. 

We calculate an index of hydrogen deficiency of three. A quick glance at the infrared spectrum reveals the source of unsaturation implied by an index of three a nitrile group at 2260 cm (index = two) and a carbonyl group at 1747 cm (index = one). The frequency of the carbonyl absorption indicates an unconjugated ester. The appearance of several strong C—O bands near 1200 cm confirms the presence of an ester functional group. We can rule out a CM2 bond because they usually absorb at a lower value (2150 cm ) and have a weaker intensity than compounds that contain C=N. 

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