Proton induced methyl group shifts in gaseous xylenium ions. Distinguishing isomers by gas-phase titration

Gas-phase titration of C7H9+ ion mixtures by FT-ICR mass spectrometry: Semiquantitative determination of ion populations generated by CI-induced protonation of C7H8 isomers and by EI-induced fragmentation of some monoterpenes

“…For example, the gas-phase basicities (GB) and proton affinities (PA) of 1,3,5-cycloheptatriene [27] and 6-methylfulvene [28] have been determined, adding to the corresponding data of toluene and 2,5-norbornadiene published previously [10, 29,30]. Furthermore, various recent experimental and computational work, including mostly the homologues and analogues of C7H9 + ions, including benzenium [31,32] and the xylenium ions [33][34][35] and protonated alkylcycloheptatrienes [36] have provided much insight into the parameters governing the unimolecular isomerization and fragmentation of these evenelectron carbocations.…”

The gas-phase basicities of 6-methylfulvene and 6,6- dimethylfulvene as determined by the thermokinetic method

“…Lower alkylbenzenium ions such as protonated toluene or xylene have been investigated mainly with respect to their bimolecular gas-phase ion chemistry. 5 Only a few studies were carried out on the unimolecular reactivity of lower toluenium or xylenium ions in the gas phase.…”

A preconcentrator coupled to a GC/FTMS: Advantages of self-chemical ionization, mass measurement accuracy, and high mass resolving power for GC applications

“…Here, we demonstrate that high mass resolving power and ion-trapping capabilities of FT-ICR mass spectrometry can be utilized to differentiate GC eluted ␣-pinene and camphene isomers in real time. Other researchers reported isomer differentiation based on multiphoton ionization and dissociation (MPI/MPD) [33], GC/MPI-FTMS [34], FTMS proton affinity bracketing [35], collision-induced dissociation (CID) [36 -38], CID combined with chromatography [39], ion-molecule reactions combined with chromatographic techniques [40], oxygen negative chemical ionization (ONCI) [41], NCI GC [42], charge inversion MS [43], and by metal oxide sensors [44]. Modifying chromatographic parameters such as GC temperature programming or column type that can alter elution time and/or order will not change mass spectral appearances.…”