Mass spectra of substituted and annelated benzofurazan-1-oxides

Electron impact positive ion spectra of ten substituted or annelated benzofurazan-1-oxides are reported. While most of the molecular ions lose either NO˙ + NO˙, or NO˙ + CO, some also lose CO as an initial fragment. One of the fragmentation pathways for 4-methylbenzofurazan-1-oxides involves initial ˙CHO loss. With the annelated benzofurazan-1-oxides (naphtho1,2-c]furazan oxide and quinolo3,4-c]furazan oxide), loss of N₂O₂ is followed by a retro-Diels–Alder elimination of butadiyne or propynenitrile, respectively from the aryne radical cation. In the case of quinolo5,6-c]furazan oxide, loss of N₂O₂ from the molecular ion must be followed by substantial rearrangement to enable the observed loss of propynenitrile to take place.