Mass spectral and pyrolytic fragmentation paths for o-nitroanisole

The mass spectral and pyrolytic dissociations of o-nitroanisole are reported. The parent ion dissociates by two pathways, principally through loss of CH₂O, but a significant fraction through loss of NO. The parent-less-30 peak is therefore a doublet, as shown by high resolution measurements. The thermal decomposition at 600°C and above proceeds also by two pathways, but these are the loss of HNO and HNO₂, to form 1,2-methylenedioxybenzene and benzaldehyde respectively.