57546-39-1Relevant academic research and scientific papers
Protonated benzene: A case for structural memory effects?
Schroeder, Detlef,Loos, Jessica,Schwarz, Helmut,Thissen, Roland,Dutuit, Odile
, p. 9931 - 9937 (2004)
Photoionization tandem-mass spectrometry of selectively deuterium labeled precursor molecules is used to probe the structure of protonated benzene which had been questioned in a provocative publication by Mason and co-workers (J. Chem. Soc., Chem. Commun. 1995, 1027). Specifically, we address the intriguing aspect of a postulated delayed hydrogen ring-walk by modulating the internal energy content of mass-selected C6H7-nDn + ions. To this end, ionization of selectively deuterated precursors by tunable synchrotron photons is combined with chemical monitoring of H +/D+ transfer from C6H7-nD n+ to a strong base B. The resulting BH +/BD+ ratios monotonically decrease with increasing internal energy content and, due to the virtue of the regioselective deuterium label incorporations, thereby disprove a delayed hydrogen ring-walk or any other "structural memory effect" in C6H7-nD n+ ions. As a consequence, the experimental studies of Mason et al. were reconsidered using sector-field mass spectrometry. These extensive studies suggest that the previous observations might have been obscured by a combination of isobaric impurities, metastable-ion contributions, and artifact signals.
A Study of Gaseous Benzenium and Toluenium Ions generated from 1,4-Dihydro- and 1-Methyl-1,4-dihydro-benzoic Acids
Kuck, Dietmar,Schneider, Jens,Gruetzmacher, Hans-Friedrich
, p. 689 - 696 (2007/10/02)
Gaseous benzenium C6H7(1+) (1) and toluenium C7H9(1+) (2) ions have been generated by mass spectrometric loss of .CO2H from the corresponding 1,4-dihydrobenzoic acids (3) and (4), and their fragmentations after ca. 10 μs have been investigated by means of mass-analysed ion kinetic energy (MIKE) spectrometry of some 2H and 13C labelled analogues.Metastable C6H7(1+) ions eliminate H2 after proton randomization, whereas metastable C7H9(1+) ions expel both H2 and CH4 after incomplete proton equilibration.In particular, 40percent of C7H9(1+) ions randomize all their carbon and hydrogen atoms prior to loss of CH4, and 60percent of C7H9(1+) ions lose the original methyl group along with a hydrogen atom from the (proton-equilibrated) benzenium ring, accompanied by a slow and incomplete exchange between the hydrogen atoms of the ring and the methyl group.It is suggested that loss of both CH4 and H2 occur via the (ipso-)toluenium ion (2).The role of a non-classical C7H9(1+) isomer, phenylmethonium ion (6), is discussed since striking similarities are found compared * adducts from ion-molecule reactions described in the literature.
