PAN

Peroxyacetyl nitrate, or PAN for shorthand, is an organic compound consisting of oxygen, and nitrogen as well as a short hydrocarbon chain. It is a principle secondary pollutant in photochemical smog. PAN is both toxic and irritating. At very low concentrations of only a few parts per billion it causes eye irritation. Plants are very sensitive: a fraction of 1ppm causes extensive damage to vegetation.

The formula for one such example of PAN is CH₃-COO-O-NO₂, and consists of a hydrocarbon, nitrogen dioxide, ester and ether group. The formula could be written as C₂HO₄N.