Some aspect of the doubly‐charged ion chemistry of armoatic amines and diamines

Abstract

Doubly-charged ion mass spectra of aromatic amines and diamines, as opposed to those of the aromatic hydrocarbons, show strong correlation with empirical formula. [MI++ is usually the base peak in the spectrum and its main fragmentation involves loss of C,H,, in sharp contrast with the [MI+. ion which always loses HCN. Measurement of the kinetic energy released in chargeseparation reactions can yield useful structural information. Results strongly support the concept of charge-localization on nitrogen atoms. Extensive scrambling prior to fragmentation was observed in all isomeric compounds studied.

Production of Long-Lived Benzene Dications from Electron Impact in the 20–2000 eV Energy Range Combined with the Search for Global Minimum Structures

“…It should be noted that the parent dications of fluorobenzene (C 6 H 5 F 2+ ) and aniline (C 6 H 7 N 2+ ) are observed in the experiments of the present work. Accordingly, these doubly charged species were also observed in previous works: C 6 H 5 F 2+ via unimolecular charge separation reactions and double-charge transfer , and C 6 H 7 N 2+ by CE and laser beam irradiation. , …”

“…Accordingly, these doubly charged species were also observed in previous works: C 6 H 5 F 2+ via unimolecular charge separation reactions and doublecharge transfer 75,76 and C 6 H 7 N 2+ by CE and laser beam irradiation. 24,77 Yields of Doubly Charged C 6 H n 2+ Species: Chlorobenzene and Benzene. The ratios of doubly to singly charged parent ion without/with loss of hydrogen atoms are shown in Figure 6 as a function of the electron impact energy for benzene.…”

“…Over the years, experimental studies were conducted for investigating the double ionization of benzene upon electron − and photon impact, the latter using discharge lamps , or synchrotron radiation − as ionization sources. Doubly charged ions were analyzed using distinct spectroscopic techniques, covering time-of-flight mass spectrometry (TOF-MS), multiparticle coincidence detection, such as threshold photoelectron–photoelectron, photoelectron–photoion, and photoion–photoion coincidence techniques, as well as charge exchange (CE) doubly charged ion mass spectroscopy. − In spite of this great effort, to the best of our knowledge, there is still no comprehensive study on the formation of doubly charged species combining a wide range of impact energies and a variety of aromatic compounds bearing distinct substituents.…”

Fragmentation reactions of molecular ions and dications of indoleamines

“…The study of multiply-charged ions 1,2 has always been a subject of interest in mass spectrometry, since it can give information about ion structures, through the measurement of the kinetic energy released upon charge separation reactions. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] The first example presented in the literature 6 refers to the fragmentation of the doubly-charged benzene molecular ion, where the kinetic energy (2.8 eV), released in the reaction C 6 H 6 2+ → C 5 H 5 + CH 3 + , corresponds to an intercharge distance of 5.14 Å. This distance is considerably larger than the one expected for a cyclic structure (2.8 Å), providing a strong indication for a linear configuration for the transition state.…”