ELECTRON-IMPACT INDUCED FRAGMENTATION OF SPIRO-1-PYRAZOLINES

The positive-ion electron impact mass spectra of twelve spiro-1-pyrazolines have been recorded at 70 eV electron energy and the data 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.