N-Benzylidene-2-nitrobenzenesulfenamide and 1-Nitro-2-(phenylthio)benzene: Comparison of Their Behavior on Flash Vacuum Pyrolysis and Under Electron Impact

Abstract

The molecular ion of N-benzylidene-2-nitrobenzenesulfenamide (1) loses SO₂ and N₂ and gives a base peak at m/z 165, C₁₃H₉, and another abundant peak at m/z 166, C₁₃H₁₀. Analysis, by gas chromatography/mass spectrometry and by preparative thin-layer chromatography, of the products of flash vacuum pyrolysis at 500-800°C of (1) showed no detectable hydrocarbon, but dibenzothiophen (mol. wt 184) was isolated and identified. The abundance of m/z 184 in the positive-ion mass spectrum of (1) is about 1%.

In the mass spectrum of 1-nitro-2-( phenylthio )benzene (2a) the base peak is at m/z 167, C₁₂H₉N, and there is a fragment ion at m/z 184, C₁₂H₈S (35%). However, carbazole (3) could not be isolated from the flash vacuum pyrolysis products, but dibenzothiophen (4) was obtained in increasing yield as the pyrolysis temperature was raised from 500 to 800°C. It is clear from these results that drawing analogies between electron impact mass spectra and flash vacuum pyrolysis results is somewhat hazardous.