The N–H Stretching Absorption Band Intensities in Secondary Amides, Secondary Thioamides, and Anilides

Abstract The intensities of the N–H stretching absorption bands of a number of N-methylamides, N-methylthioamides and anilides have been measured in a solution of carbon tetrachloride. It was observed that the intensities of the N–H stretching absorption bands of N-methylacetamide and N-methylpropionamide are considerably higher than those of the same band in the corresponding anilides. On the other hand, the intensity of the N–H stretching absorption band of N-methylformamide is of the same order as that of formanilide. The pattern of variation of the intensity of the N–H streching absorption bands in these compounds is similar to that of the C=O stretching absorption bands of the same compounds, but the variation in their frequencies is different. It was also observed that the intensities of the N–H stretching bands of N-methylthioamides are considerably higher and their frequencies are lower than those of the corresponding secondary amides.