[nbd]

My IR spectra correlation chart says that the stretch for a nitro N-O bond occurs at "1550 and 1400cm^-1" and that it will look like "teeth". Why does N-O have two peaks? The rest of the functional groups on my chart list a range in which a single peak should appear, but why is N-O expected to generate two peaks?

Thanks!

[J1800]

From a symmetric and asymmetric stretch, as seen in water: