Knowledge Bank

“A survey of the infrared spectra of primary and secondary aliphatic amines has provided some new spectra-structure correlations. Primary amines have strong broad absorption bands at 815 $\pm$ $35cm-1$, while secondary amines have similar bands at 730 $\pm$ $25cm-1$. These bands are associated with bending vibrations of the H-N-H and C-N-H bonds. In addition, secondary amines have strong bands at 1160 $\pm$ $30cm-1$ and primary amines have much weaker absorptions at 1085 $\pm$ $45cm-1$. A normal coordinate treatment of four-body models of the type $R2NH2$ and $R2NH2$, assuming $Ca$ symmetry, has been helpful in understanding the nature of amine vibrations.”