Structure and reactivity of gas-phase ions: C4H4.bul.+

Ion-molecule reactions and collision-activated dissociation of C4H4+. isomers: A case study in the use of the MS3 capabilities of a pentaquadrupole mass spectrometer

“…action kinetics of C 4H!' with benzene (18) (and later acetylene (19)) provided support for the existence of both linear and cyclic ions, as first suggested by the thermochemical data. However, studies of metastable ions [17, 18b] and CAD [18b) by most investigators supported the conclusion that the structure of C 4H!'…”

Kinetics of electron impact ionization and ion-molecule reactions of pyridine

“…Given reasonable uncertainties in the measured quantities and the generally accepted validity of the Langevin rate, it most likely indicates that these reactions are very effective. C 4 H 4 + generated from electron impact ionization of pyridine as well as benzene, etc., is considered to consist of two isomers, vinylacetylene and methylene cyclopropene [4,7,9], which have been found to have different reactivities towards benzene or acetylene: one isomer reacts readily while the other one is essentially unreactive [4,7]. In a study by Shay et al [29] four different isomers of C 4 H 4 + were found to be formed from different neutral precursors, namely, vinylacetylene, butatriene, methylene cyclopropene, and nonaromeatic cyclobutadiene, which undergo significantly different ion-molecule reactions with allene, isoprene, furan, and thiophene.…”

“…The dissociative ionization of pyridine has been one of the topics of debate for decades in the area of mass spectrometry, especially with regard to the isomer composition of the product ion C 4 H 4 + , the fragmentation mechanism, and the appearance energies of the product ions [1][2][3][4][5][6][7][8][9][10][11]. The reactions of ions generated from the ionization, including collision-induced dissociation (CID), have been studied [4,5,7].…”

“…The reactions of ions generated from the ionization, including collision-induced dissociation (CID), have been studied [4,5,7]. In this paper we report the results of our recent measurement on absolute dissociative ionization cross-sections of pyridine by electron impact.…”

Surface-Induced Dissociation of the Benzene Molecular Cation in Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

“…58 Detailed CID studies as well as neutralization-reionization experiments revealed that the two isomers are methylenecyclopropene (I) and vinylacetylene (II). [59][60][61] Because the linear isomer II is less stable than the cyclic isomer I by 20 kJ/mol, we assumed that a major part of the C 4 H 4 + observed in the SID spectra has the methylenecyclopropene structure. Vibrational frequencies of methylenecyclopropene were adopted from ref 62 (Supporting Information).…”