Bond formation upon electron—impact

Cooks, R. Graham

doi:10.1002/oms.1210020505

Cited by 87 publications

(21 citation statements)

References 183 publications

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“…This is particularly important due to the energetically unfavourable formation of a radical product ion from an even-electron precursor. 18 However, the resonance stabilisation across the two aromatic rings, and the sulfone and sulfoxide functionalities, is likely to facilitate this dissociation. Both proposed dissociation mechanisms involve the loss of dimethylamine.…”

Section: Resultsmentioning

confidence: 99%

High‐throughput approaches towards the definitive identification of pharmaceutical drug metabolites. 2. An example of how unexpected dissociation behaviour could preclude correct assignment of sites of metabolism

Holman

Wright

Langley

2009

Rapid Comm Mass Spectrometry

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The low-energy collision-induced dissociation product ion spectra of protonated beta-blockers reveal an analogy to fragmentation under electron ionisation conditions", J. Mass Spectrom. 2011Spectrom. , 1182Spectrom. -1185 S.W. Holman, P. Wright, N.J. Wells and G.J. Langley, "Evidence for site-specific intra-ionic hydrogen/deuterium exchange in the low-energy collision-induced dissociation product ion spectra of protonated small molecules generated by electrospray ionisation" J. Mass Spectrom. 2010, 45, 347-357 Abstract S-oxidation is a common metabolic route for sulphur containing compounds. When studying the fragmentation of some chemically synthesised sulphoxides, two unexpected losses of 62 m/z units were observed in the collision-induced dissociation (CID) product ion spectrum protonated 3-dimethylaminomethyl-4-(4-methanesulfinyl-3-methyl-phenoxy)-benzenesulfonamide. A single loss was initially assigned using the low resolution product ion spectrum, acquired by electrospray ionisation-quadrupole ion trap-mass spectrometry (ESI-QIT-MS), as methanethial, S-oxide with the dissociation proceeding via a charge-remote, four-centred rearrangement. This assignment was consistent with well-documented hydrogen rearrangements in the literature. Further, the loss was not observed for the parent compound. Thus, it was inferred that the site of metabolism was involved in the dissociation and the attractive nature of the four-centred rearrangement meant that the loss of methanethial, Soxide was a logical assignment. However, deuterium labelling experiments and accurate mass measurements, performed using electrospray ionisation-Fourier Transform Ion Cyclotron Resonance-mass spectrometry (ESI-FTICR-MS), showed that two distinct losses of 62 m/z units occur, neither of which was of that initially hypothesised from the low resolution product ion spectrum of the protonated molecule. Mechanisms consistent with the experimental findings are postulated. An MS 3 spectrum of the fully exchanged, deuterated species supported the proposed mechanisms by suggesting that 3-dimethylaminomethyl-4-(4-methanesulfinyl-3-methyl-phenoxy)-benzenesulfonamide has multiple sites of protonation in the gas phase. The planar structures of the posited product ions are likely to provide the driving force for the rearrangements. The relevance of the observations with regards to pharmaceutical drug metabolite identification are discussed.

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Section: Resultsmentioning

confidence: 99%

High‐throughput approaches towards the definitive identification of pharmaceutical drug metabolites. 2. An example of how unexpected dissociation behaviour could preclude correct assignment of sites of metabolism

Holman

Wright

Langley

2009

Rapid Comm Mass Spectrometry

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“…By analogy with 1-phenyl pyridone (16), loss of H' from the ortho position of the phenyl ring combined with new bond formation to the carbonyl oxygen would generate a [M -H]+ ion with the stable oxazolium structure 16. Aryl-oxygen bond formation in odd-electron ions with H' elimination has been postulated in the fragmentation of Pdiketones and a,P-unsaturated esters and acids (18), and an analogous process has been proposed in the mass spectra of pyridinium oxides (19). However, the absence of metastable peaks of significant intensity for D' loss from 13 leads us to suggest that formation of 16 is, at best, a minor process in the fragmentation of 12 in the metastable time frame.…”

Section: Resultsmentioning

confidence: 99%

The mass spectra of pyrimidines: 2(1H)-pyrimidinone and some N(1)-substituted derivatives

Rye¹,

Tee²,

Kazdan³

1982

Can. J. Chem.

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The EI induced fragmentation of 2-pyrimidinone (1) and several N(1)-substituted derivatives has been studied. Principal fragmentation pathways have been identified using 2H labelling, metastable defocussing, and exact mass measurements.The fragmentation of 1 parallels that of cytosine. The hydrogen atom at C(4), and not the tautomeric hydrogen, is involved in the formation of the prominent [M – H]+ peak in the spectrum of 1; subsequent fragmentations of the [M – H]+ moiety contribute significantly to the spectrum.Side chain eliminations predominate in the mass spectra of the N(1)-substituted derivatives, but peaks characteristic of the pyrimidinone nucleus are observable in every case. Alternative structures for the [M – H]+ entity formed by H• loss from the substituent are proposed for the N-phenyl and N-benzyl compounds.

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“…for conversion of [l]" and [2]" to [3]+' can be obtained by labelling experiments.6 From labelling work it appears that C6H,' and C6H6 lost from metastable ions of 1 and 2 originate from both phenyl groups of the molecular ions.6 For the loss of C6H6 simple Gaussian peaks are observed for 2, 3 and 5. For 1 the peak is complex, as the n-values differ by 0.3 and are too low for a real Gaussian peak.…”

Section: Rearrangements and Fragmentations Of Phenyl Styryl Sulfides-1mentioning

confidence: 99%

“…However, as these n-values are rather low for a simple Gaussian peak, fragmentation of compound 2 could still involve a composite metastable transition. A rearrangement of [2]" to [31+' would lead to ions [3]" with high internal energy, that decompose along both reaction pathways (Scheme 3). The measured To.5 value for 2 (65meV) suggests a greater contribution of low energy ions than observed for 1 and 4.…”

Section: Rearrangements and Fragmentations Of Phenyl Styryl Sulfides-1mentioning

confidence: 99%

Rearrangements and fragmentations of phenyl styryl sulfides: 1—Metastable ion spectra

Dijkstra

Weringa

1982

Org. Mass Spectrom.

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The mass spectra of two isomeric phenyl styryl sulphides show abundant peaks for fragment ions formed after interesting and unusual rearrangements, e.g. loss of CHS' and C,H,'. Information about these rearrangements was obtained by comparison of the metastable peak intensities and peak shapes with those of four isomers. It appears that isomerization reactions between the phenyl styryl sulfides and the isomers are possible and that most of the metastable ion fragmentations proceed via reacting configurations that are common to two or more of the compounds investigated. The results indicate that an earlier proposed mechanism for the fragmentation of phenyl vinyl sulfides is incomplete and only partly correct for the compounds studied. Metastable ion spectra were obtained using high voltage scans and constant B/E scans: a short comparison of the results obtained with the two methods is given.

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Bond formation upon electron—impact

Cited by 87 publications

References 183 publications

High‐throughput approaches towards the definitive identification of pharmaceutical drug metabolites. 2. An example of how unexpected dissociation behaviour could preclude correct assignment of sites of metabolism

High‐throughput approaches towards the definitive identification of pharmaceutical drug metabolites. 2. An example of how unexpected dissociation behaviour could preclude correct assignment of sites of metabolism

The mass spectra of pyrimidines: 2(1H)-pyrimidinone and some N(1)-substituted derivatives

Rearrangements and fragmentations of phenyl styryl sulfides: 1—Metastable ion spectra

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