Assigning Structures to Ions in Mass Spectrometry

Holmes, John L.; Aubry, Christiane; Mayer, Paul M.

doi:10.1201/9780203492475

Cited by 79 publications

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“…In this study we have used tandem mass spectrometry based experiments in conjunction with model chemistry calculations to probe the rich dissociation chemistry of the metastable molecular ions NH 2 OCH 2 CH 2 OH •+ (AE-1). These ions dissociate via six competing pathways whereas the related 1,2-ethane diol ion HOCH 2 CH 2 OH •+ only loses HCO • in the metastable timeframe [3,4] via a mechanism that features proton-transport catalysis (PTC) [5] in hydrogen-bridged radical cations (HBRCs) [6] as key intermediates. It will be shown that HBRCs also play a key role in the various dissociation reactions of low-energy 2-aminoxyethanol radical cations.…”

Section: Introductionmentioning

confidence: 99%

The remarkable dissociation chemistry of 2-aminoxyethanol ions NH2OCH2CH2OH+studied by experiment and theory

Jobst¹,

Ruttink²,

Terlouw³

2008

International Journal of Mass Spectrometry

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Low-energy 2-aminoxyethanol molecular ions NH 2 OCH 2 CH 2 OH•+ exhibit a surprisingly rich gas-phase ion chemistry. They spontaneously undergo five major dissociations in the microsecond timeframe, yielding ions of m/z 61, 60, 46, 32 and 18. Our tandem mass spectrometry experiments indicate that these reactions correspond to the generation of HOCH 2 CH(OH) + (protonated glycolaldehyde), HOCH 2 C( O)H •+ (ionized glycolaldehyde), HC(OH)NH 2 + (protonated formamide), CH 2 OH 2 •+ (the methylene oxonium ion) and NH 4 + . A mechanistic analysis of these processes using the CBS-QB3 model chemistry shows that the molecular ions undergo a 1,4-H shift followed by a facile isomerization into the ion-molecule complex [HOCH 2 C( O)H•+ ]· · ·[NH 3 ] which acts as the reacting configuration for the five exothermic dissociation processes. Analysis of the D-labelled isotopomer ND 2 OCH 2 CH 2 OD•+ , in conjunction with our computational results, shows that proton-transport catalysis may be responsible for the partial conversion of the m/z 60 glycolaldehyde ions into the more stable 1,2-dihydroxyethene isomer HOC(H) C(H)OH•+ .

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Section: Introductionmentioning

confidence: 99%

The remarkable dissociation chemistry of 2-aminoxyethanol ions NH2OCH2CH2OH+studied by experiment and theory

Jobst¹,

Ruttink²,

Terlouw³

2008

International Journal of Mass Spectrometry

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“…Two reviews 4,5 that appeared in the 1970s showed inter alia, the increasing power of deuterium labelling experiments to uncover hidden hydrogen rearrangements, some of which were fully revealed by labelling, but only in conjunction with observations of the dissociation chemistry of metastable ions. 6 Metastable ion (MI) mass spectra uniquely permit the study of the few, lowest energy fragmentations of a mass-selected ion and so can provide very specific information as to the fate of the label. An early example is that of ionized benzoic acid, C 6 H 5 COOH Á + .…”

Section: Introductionmentioning

confidence: 99%

“…The resulting CID mass spectra contain vital structural information and the experi- The original ZAB instrument has been further developed into a veritable ion-chemistry laboratory 14 and the full range of experimental techniques now accessible with such mass spectrometers has been surveyed in a recent book. 6 To summarize the present state of gas-phase ion chemistry experiments, we are now able to measure the energetics of ions and their dissociation reactions (the study of ionization and appearance energies), to investigate in detail, with the assistance of isotopic labelling, the mechanisms of their unimolecular reactions, to identify the structures of the neutral species lost in fragmentations and even to observe the chemistry of ions' neutral counterparts. The final task of constructing a complete potential energy surface for the chemistry of an organic ion can be achieved with the aid of contemporary methods in computational chemistry, methods based on ab initio molecular orbital theory and/or density functional theory.…”

Section: Introductionmentioning

confidence: 99%

“…The final task of constructing a complete potential energy surface for the chemistry of an organic ion can be achieved with the aid of contemporary methods in computational chemistry, methods based on ab initio molecular orbital theory and/or density functional theory. 6,15 These methods permit one to compute the relevant potential energy surface for an organic ion and (all, or many of) its isomers, including the transition states between them, and for all the low-energy unimolecular dissociations (metastable ions) that they may undergo. Note that these results also relate to the reverse ionmolecule or ion-radical reactions and so, for example, they have great relevance for upper atmosphere and interstellar processes.…”

Section: Introductionmentioning

confidence: 99%

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Isotopic labelling in mass spectrometry as a tool for studying reaction mechanisms of ion dissociations

Holmes¹,

Jobst²,

Terlouw³

2007

Labelled Comp Radiopharmac

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Perhaps the greatest influence that isotopic labelling experiments have had on organic mass spectrometry is that reaction mechanisms originally borrowed from the chemistry of neutral counterparts have proved to be inadequate for explaining the results. It was therefore necessary to devise completely new types of fragmentation mechanisms and unconventional structures for organic gas-phase cations. In most cases the labelling technique allows one to discover the positions at which the label atoms are found in both the charged and neutral products of an ion's dissociation. These experimental results are often difficult to rationalize by any simple mechanism, but they nearly always indicate how chemical computations should be directed in order for the latter to be able to provide a better mechanistic understanding. This short article describes some significant studies involving D and 18-O labelling that well support the above assertions, using as examples the behaviour of some quite simple organic molecules.

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“…The prominent m/z 43 peak undoubtedly represents the acetyl cation, CH 3 C=O + [15]. Tandem mass spectrometry experiments [15] performed using the ZAB-R instrument [12] indicate that this ion is likely formed by the route depicted in Scheme 3.…”

Section: Identification Of the Disinfection By-products Dbp-a Dbp-bmentioning

confidence: 99%

Identification of Halohydrins as Potential Disinfection By-Products in Treated Drinking Water

Jobst

Taguchi

Bowen

et al. 2011

International Journal of Spectroscopy

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In 2001, two potential disinfection by-products (DBPs) were tentatively identified as 1-aminoxy-1-chlorobutan-2-ol (DBP-A) and its bromo analogue (DBP-B) (Taguchi 2001). Subsequently it became clear, by consulting an updated version of the NIST database, that their mass spectra are close to those of the halohydrins 4-chloro-2-methylbutan-2-ol and 3-bromo-2-methylbutan-2-ol. To establish the structures of these DBPs, additional mass spectrometric experiments, including Fourier transform ion cyclotron resonance (FTICR), were performed on treated drinking water samples and authentic halohydrin standards. It appears that DBP-A is 3-chloro-2-methylbutan-2-ol and that DBP-B is its bromo analogue. DBP-B has been detected in ozonated waters containing bromide. Our study also shows that these DBPs can be laboratory artefacts, generated by the reaction of residual chlorine in the sample with 2-methyl-2-butene, the stabilizer in the CH 2 Cl 2 used for extraction. This was shown by experiments using CH 2 Cl 2 stabilized with deuterium labelled 2-methyl-2-butene. Quenching any residual chlorine in the drinking water sample with sodium thiosulfate minimizes the formation of these artefacts.

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Assigning Structures to Ions in Mass Spectrometry

Cited by 79 publications

References 0 publications

The remarkable dissociation chemistry of 2-aminoxyethanol ions NH2OCH2CH2OH+studied by experiment and theory

The remarkable dissociation chemistry of 2-aminoxyethanol ions NH2OCH2CH2OH+studied by experiment and theory

Isotopic labelling in mass spectrometry as a tool for studying reaction mechanisms of ion dissociations

Identification of Halohydrins as Potential Disinfection By-Products in Treated Drinking Water

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