IR Peak Splitting in Amines and Nitro Groups

IR peak splitting can reveal how identical bonds in a polyatomic group are moving. These bonds may stretch in phase, which is symmetric stretching, or out of phase, which is asymmetric stretching. The two motions often create different IR peak shapes and positions.

As a general rule, asymmetric s...

Recall that a polyatomic group bearing a minimum of two identical atoms can stretch symmetrically or asymmetrically.

So, the two N–H bonds of RNH₂ either stretch in phase as symmetric stretching, or out of phase exhibiting asymmetric stretching.

Thus, RNH₂ give rise to two distinct IR peaks in the range of 330...