Mass spectra of 3-nitro-2H-chromenes and 3-nitrochromans

Abstract

The 4kV, 70 eV electron impact mass spectra (e.i.-m.s.) of eight 2-aryl-3-nitro-2H-chromenes and ten 2-aryl-3-nitrochromans of diverse functionality are reported and discussed. The peak due to the molecular ion is always appreciable and often intense in these spectra. Loss of NO2 from M+˙ is responsible for the base peak in the nitrochromene spectra. In contrast, [M– HNO2]+˙ is more abundant than [M– NO2]+ in the spectra of the nitrochromans; furthermore, this unusual HNO2 loss persists even for metastable molecular ions. A diagnostically important ion, of nominal structure [ArCH2]+, accounts for the base peak in the chroman spectra; this ion, which defines the formula of the 2-aryl subsituent, corresponds to elimination of benzofuran from [M– NO2]+.All the compounds studied exhibited [M]–˙ ions in their electron capture negative ion chemical ionisation (c.i.) spectra. Apart from [M]–˙ and the base peak at [M– NO2]–, few ions were of considerable abundance in these spectra, although [NO2]– ions were present in the nitrochroman series.