The mass spectra of benzofuroxans—an example of an ortho effect

The fragmentation behavior of a series of nine benzofuroxans has been studied under electron impact conditions. It was found that benzofuroxans without a nitro group in the 4-position fragment principally through loss of N₂O₂ (the furoxan ring), whereas those with a nitro group ortho to the furoxan ring exhibit predominant loss of NO from position 1 of the furoxan ring.