Mass spectrometry study on five‐substituted pyrroles and the related N‐methylene‐ 1,3,4‐thiodiazoles

Abstract

Electron impact mass spectra of nine new substituted pyrroles are reported. Apart from compounds 1a and 1b, the other seven compounds produce R1--Ph--C≡O+ ions as base peaks. Except for compounds 2a–c, each compound may produce [M−EtOH]∔, [M−OEt]+ and other fragment ions. The proposed fragmentation mechanisms of the six new compounds giving M∔ ions have been supported by mass analysed ion kinetic energy spectrometry and accurate mass data. No molecular ion peaks of compounds 2a–c are observed under electron impact conditions. However, very intense protonated molecule peaks of compounds 2a–c were observed under fast atom bombardment conditions together with [M+H − EtOH]+ ions. By D-exchange experiments, it was verified that the proton is localized on the N atom between the carbonyl and thiocarbonyl groups during the formation of protonated molecules. © 1998 John Wiley & Sons, Ltd.