Electron‐impact induced fragmentation of spiro‐1‐pyrazolines

Abstract

AbstractThe positive‐ion electron impact mass spectra of twelve spiro‐1‐pyrazolines have been recorded as 70 eV electron energy and the dat analyzed to elucidate their fragmentation pathways. None of these compounds gave abundant molecular ions (M+) due to the instability of the pyrazoline ring. The first step in the decomposition of M+ ions is the elimination of a nitrogen molecule followed by a rearrangement resulting in the formation of the cation radical [M–28]+, the decomposition of which is discussed in detail. The proposed fragmentation pathways and their mechanisms are supported by high‐resolution data, linked‐scan measurements at constant B/E and collision‐induced dissociation‐mass‐analyzed ion kinetic energy spectra.