title: Energy-variable collision-induced dissociation study of 1,3,5-trisubstituted 2-pyrazolines by electrospray mass spectrometry.
abstract: The pathways of the ([M+H](+)) ions generated from electrosprayed solutions of nine 1,3,5-trisubstituted 2-pyrazoline derivatives were studied using energy-variable collision-induced dissociation (CID) and pseudo-MS(3) (in-source CID combined with MS/MS) methods. It was shown that under CID conditions several structurally important product ions such as the 2,4-substituted azete and 1,2-substituted aziridine ions were formed. The compositions of the product ions were unambiguously supported by accurate mass measurement (mass accuracy was within +/- 8 ppm). The fragmentation pathways of 1,3,5-trisubstituted 2-pyrazolines were established by means of pseudo-MS(3). It was found that a substituent at the N-1 position greatly affects the fragmentation pathways of the 2-pyrazoline derivatives. The 1-acetyl- and 1-propionyl-2-pyrazoline derivatives dissociate mainly through formation of a pyrazolium cation, while in the case of 1-phenyl-2-pyrazoline derivatives product ions arising from the consecutive fragmentation of 2,4-substituted azete and 1,2-substituted aziridine ions dominate. Another interesting finding is the formation of a radical cation from the 2,4-substituted azete by loss of a methyl radical. The fragmentation yield as a function of the collision energy for each of the 1,3,5-trisubstituted 2-pyrazolines was determined. Based on the fragmentation yield versus collision energy curves the relative fragmentation stabilities for the 1,3,5-trisubstituted 2-pyrazoline derivatives were also evaluated.
authors.affiliation: Department of Applied Chemistry, University of Debrecen, Egyetem tér 1, H-4010 Debrecen, Hungary.
authors.forename: Sándor
authors.initials: S
authors.lastname: Kéki
authors.forename: Lajos
authors.initials: L
authors.lastname: Nagy
authors.forename: János
authors.initials: J
authors.lastname: Török
authors.forename: Katalin
authors.initials: K
authors.lastname: Tóth
authors.forename: Albert
authors.initials: A
authors.lastname: Lévai
authors.forename: Miklós
authors.initials: M
authors.lastname: Zsuga
mesh_terms: D000465:Algorithms; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D011720:Pyrazoles / Q000032:analysis*; D021241:Spectrometry, Mass, Electrospray Ionization; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D007202:Indicators and Reagents; D011720:Pyrazoles