N-H combination band from primary amides

N-H combination band from primary amides N-H [vN-H asymmetric and Amide N-H combination bmd 1 3... 

N-H/C-N combination band from primary amides (R-C=0-NH2) N-H [vN-H symmetric and amide Primary amides ... 

There is some correlation between molecular structure and band position for certain bands, but because these are often overtone and combination bands, their positions are not as structure-dependent as the fundamental bands in the mid-IR. For example, primary amines, both ahphatic and aromatic, have two absorption bands, one at about 1500 nm and the second at about 1990 nm. Secondary amines have only one band at about 1500 nm. As expected, a tertiary amine has no NH band. Amides with an — NH2 group can be distinguished from R— NH—R amides by the number and position of the N—H bands. The reference by Goddu has a detailed table of NIR structure-wavelength correlations. 

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