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.

Ultrasound-Promoted Synthesis, Structural Characterization and in vitro Antimicrobial Activity of New 5-Aryl-3-(2-hydroxyphenyl)-4,5-dihydro-1H-pyrazole-1-carboximidamides

“…25 Moreover, the fragmentation pathway has important information about the molecular structure. For the title compounds, it is similar to that proposed by Kéki et al, 26 for 1,3,5-trisubstituted pyrazolines, as well as dos Santos et al 27 for dihydropyrimidines. The Figure 1 demonstrates this HRMS tools used to characterize the synthesized amidino pyrazolines, using as example the compound 3d.…”

Q-RAI data-independent acquisition for lipidomic quantitative profiling

“…For instance, ionization efficiency is dependent on numerous factors such as basicity of the analytes and solvents, relative intensities of the analytes, type of LC-MS instrument and experimental conditions, which could all contribute to deviation in MS1 quantification. The fragmentation yield is largely dependent on collision energy and may not be the optimal one for all analytes when using a constant value 38,39 . As such, one might expect to observe less background noise for MS2 and more variability in MS1 quantitation (although a larger cohort would have to be used to further evaluate this aspect).…”

The mechanism of water loss from protonated cathinones

“…To the best of our knowledge, only Qian et al have proposed the formation of azirine structure for the [M + H − H 2 O] + ion of one cathinone, namely mexedrone . On the contrary, the formation of azirine‐ring‐containing ions has been proposed for fragmentation processes of N‐heterocyclic compounds that occurred under EI conditions, under fast atom bombardment (FAB) conditions, and under ESI conditions …”

“…In the experimental part, it is explained 21 On the contrary, the formation of azirine-ring-containing ions has been proposed for fragmentation processes of N-heterocyclic compounds that occurred under EI conditions, [22][23][24][25] under fast atom bombardment (FAB) conditions, 26 and under ESI conditions. 27 We also obtained the product ion spectra of Figure 1), and the calculated exact mass is 147.0810, so the mass accuracy is −6.1 ppm.…”