Infrared spectroscopic studies of amides and anilides

Abstract

The integrated absorption intensities of the carbonyl band in amides and anilides and of the amide II and III bands have been measured by Ramsay’s and Wilson and Well’s methods. The intensity of the C=O band in amides is considerably greater than that in anilides and ketones, and in primary amides, it has an intermediate value between those of tertiary and secondary amides. The intensity of the amide III band in N-methyl-acetamide is considerably higher than that of the same band in the other secondary and tertiary amides. The C=O and C-N stretching frequencies, recorded in different states of aggregation in primary amides, are shown to bear a linear relation. In amides, an additional absorption band appears on the lower frequency side of the free C=O stretching absorption, in the presence of iodine. The frequency difference between these absorption bands is 25 to 45 cm.−1, indicating that the oxygen atom of the carbonyl group in amides has considerable donor strength.