Gas-phase deprotonation of arylalkylamines. A collision-induced dissociation study

Cardoso, Ana M.; Alexandre, Sílvia M. G.; Barros, Cristina; Correia, António; Nibbering, Nico M. M.

doi:10.1002/(sici)1097-0231(19991015)13:19<1885::aid-rcm716>3.0.co;2-k

Cited by 4 publications

(2 citation statements)

References 8 publications

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“…This property is likely to have been enhanced by collision‐induced dissociation (CID), and Fleurat‐Lessard et al 44 noted differences in PAH proton transfers depending on structure, as did Arakawa et al 45. Cardoso et al 46 also described gas‐phase deprotonation of arylalkylamines during negative mode CID, and suggest that such proton loss occurs at benzylic positions with H 2 O as ionizing reagent. A 7‐SMBA 12‐position carbanion presumably would provide impetus for nucleophilic attack at the adjacent 1‐position resulting in a cyclopentenyl ring.…”

Section: Discussionmentioning

confidence: 99%

Mass spectrometric analysis of 7‐sulfoxymethyl‐12‐methylbenz[a]anthracene and related electrophilic polycyclic aromatic hydrocarbon metabolites

2004

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The Meso-region theory of polycyclic aromatic hydrocarbon (PAH) carcinogenesis predicts that the development of pronounced carcinogenicity depends on the introduction of a good leaving group on alkyl side-chains attached to the exceptionally reactive meso-anthracenic or L-region positions of PAHs. Thus, the first step in carcinogenesis by methylated PAHs such as 7,12-dimethylbenz[a]anthracene (DMBA) would be the hydroxylation of the L-region methyl groups, particularly the 7-methyl group. The second would be the formation of a metabolite, e.g. a sulfate ester, which is expected to be a good leaving group capable of generating a highly reactive benzylic carbocation. 7-Hydroxymethyl-12-methylbenz[a]anthracene (7-HMBA) is a metabolite of DMBA, and sulfation of 7-HMBA to a 7-sulfoxymethyl metabolite (7-SMBA) is a known Phase II metabolic process designed to facilitate excretion, but actually enabling more destructive side-reactions. These side-reactions occur with generation of an electrophilic 7-methylene carbonium ion, and/or by in vivo halide exchange to provide neutral side-products more capable of entering cells, especially those of DMBA target tissues. Electrospray ionization mass spectrometry (MS) enabled us to visualize 7-SMBA as an intact m/z 351 conjugate anion by negative mode, and as a released m/z 255 carbonium ion by positive mode. Upon prolonged refrigeration, 7-SMBA accumulated an m/z 383 photooxide, which appeared capable of re-evolving the starting material as visualized by tandem quadrupole MS, or MS/MS. The 7-SMBA carbonium ion provided interpretable fragments when studied by fragment ion MS/MS, including those representing the loss of up to several protons. Subtle differences in this property were encountered upon perturbing 7-SMBA, either by warming it at 37 degrees C for 2 h or by substituting the initial sulfoxy group with an iodo group. Side-reactions accounting for such proton losses are proposed, and are of interest whether they occur in the mass spectrometer, in solution or both; these proposals include acidity at the 12-methyl position and cyclization between the 12-methyl group and the adjacent C-1 position. It is also suggested that such side-reactions may comprise one route to relieving steric strain arising between the 12-methyl group and the angular benzo ring of 7-SMBA.

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Section: Discussionmentioning

confidence: 99%

Mass spectrometric analysis of 7‐sulfoxymethyl‐12‐methylbenz[a]anthracene and related electrophilic polycyclic aromatic hydrocarbon metabolites

2004

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“…The nitro compound formed only the molecular radical anion. The collision‐induced dissociation spectra of the deprotonated molecules appeared to be strongly dependent on the structural features of the molecules (Cardoso et al, 1999). Finally, it should be noted that various rhenium compounds and activated Re 2 O 7 /Al 2 O 3 catalysts were studied by use of negative ion fast atom bombardment.…”

Section: The Years Of Reversed Geometry Double Focusing Hybridmentioning

confidence: 99%

Four decades of joy in mass spectrometry

Nibbering

2006

Mass Spectrometry Reviews

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Tremendous developments in mass spectrometry have taken place in the last 40 years. This holds for both the science and the instrumental revolutions in this field. In chemistry the research was heavily focused on organic molecules that upon electron ionization fragmented via complex mechanistic pathways as shown by isotopic labeling experiments. These studies, including ion structure determinations, were performed with use of double focusing mass spectrometers of both conventional and reversed geometry, and equipped with various types of metastable ion scanning and collision-induced dissociation techniques developed by physical and analytical chemists. Time-resolved mass spectrometry by use of the field ionization kinetics method, developed by physical chemists, was another powerful way to unravel details of unimolecular gas phase ion dissociations. Then the development of new ionization methods, such as desorption chemical ionization, field desorption, and fast atom bombardment permitted not only to analyze unvolatile, thermally labile and higher molecular weight compounds, but also to study their chemical behavior in the gas phase, initially with use of double focusing instruments and later on with multisector and hybrid mass spectrometers. These ionization methods also enabled to study organometallic compounds and increasingly the field of medium-sized to large biomolecules, the latter being exploded in the last decade by the development of electrospray- and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry. Another area of research concerned the bimolecular chemistry of organic ions with organic molecules in the gas phase. Initially this was performed with use of among others drift-cell ion cyclotron resonance spectroscopy, that later on was replaced by the developed method of ion trapping and Fourier transform ion cyclotron resonance. Combination of the latter with the afore-mentioned ionization methods has shifted also in this case the research on organic molecules to organometallic/inorganic systems, and predominantly to biomolecules in the last decade. This invited review will describe the research efforts made by the author's group over the last 40 years together with some personal experiences during his career.

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