Fragmentation of even electron ions. Protonated ketones and ethers

Sigsby, M. L.; Day, Richard E.; Cooks, R. Graham

doi:10.1002/oms.1210140508

Cited by 60 publications

(32 citation statements)

References 35 publications

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“…Although the even-electron rule holds true for most dissociations, several exceptions to this rule have been reported. Some exceptions have been observed [51,52] for the high-energy CID of [M + H] + and [M − H] − , such as in the case of methyl elimination from protonated mycosporine [53] and deprotonated metoclopramide [54] or hydroxyl elimination from triazines. [48] Some examples of radical anions produced by CID of molecules ionized by ESI have been described for nitro compounds, [55] amines, [56] amides, [56] and flavonoids.…”

Section: Formation Of the M/z 199 M/z 173 And M/z 170 Ionsmentioning

confidence: 99%

Gas‐phase dissociation of 1,4‐naphthoquinone derivative anions by electrospray ionization tandem mass spectrometry

et al. 2009

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Gas-phase dissociation pathways of deprotonated 1,4-naphthoquinone (NQ) derivatives have been investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The major decomposition routes have been elucidated on the basis of quantum chemical calculations at the B3LYP/6-31 + G(d,p) level. Deprotonation sites have been indicated by analysis of natural charges and gas-phase acidity. NQ anions underwent an interesting reaction under collision-induced dissociation conditions, which resulted in the radical elimination of the lateral chain, in contrast with the even-electron rule. Possible pathways have been suggested, and their mechanisms have been elucidated on the basis of Gibbs energy and enthalpy values for the anions previously described at each pathway.

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Section: Formation Of the M/z 199 M/z 173 And M/z 170 Ionsmentioning

confidence: 99%

Gas‐phase dissociation of 1,4‐naphthoquinone derivative anions by electrospray ionization tandem mass spectrometry

et al. 2009

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“…On the first CH,' loss, the evenodd electron is broken but similar processes are known. 30,[47][48][49] For example, methyl radical loss is observed in the CAD product spectrum of protonated alkyl naphthalene^?^-^, The methyl radical lost does not come from the isoprene portion of the adduct ion. Evidence for this is seen in the CAD product spectrum of m/z 269 (C,,H,+ + CSH,) illustrated in Fig.…”

Section: +mentioning

confidence: 99%

Ion—molecule chemistry of pyrene in an ion‐trap mass spectrometer

Nourse

Cox

Cooks

1992

Org. Mass Spectrom.

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The quadrupole ion-trap mass spectrometer is used to investigate aspects of the ion-molecule chemistry of the pyrene molecular radical cation (M+9, the [M -HI + ion and the [M -H,] +' ion. Cycloaddition and alkyl halide addition reactions with the reagents pyrene, methyl iodide, ethyl iodide, isoprene and 2-iodopropane are investigated. The pyrene molecular radical cation is remarkably unreactive while the closed shell [ M -HI + ion is highly reactive and the [ M -H,) +' ion shows intermediate reactivity. Analogies are found between the behaviour of the pyrene molecular radical cation and the corresponding [ M -HI + ion on the one hand, and the benzene radical cation and the phenylium ion on the other. The total lack of reactivity of the M+' ion is attributed to x-delocalization of the radical and the cation over the large aromatic system. Addition of isoprene to the (M -HI + and (M -H,j + * ions of pyrene occurs via cycloaddition reactions. A characteristic fragmentation of each adduct ion is methyl radical loss and evidence obtained using pyrene-d,, indicates that the product in the case of [ M -HI + is an ionized indene. Addition of methyl iodide, ethyl iodide and 2-iodopropane to the [ M -H j + ion of pyrene occurs to give an iodonium product (C,,H9-I+-R) which fragments by loss of I' or CH,' to give the methylpyrene or iodopyrene product ions. Reactions of ethyl iodide and Ziodopropane with the dehydropyrene ion, [ M -H2] +., give primarily an HI addition product, together with small contributions from the intact adducts.Evidence is provided suggesting that in this case the HI and alkyl halide molecules add across a C-C bond rather than forming an iodine-bound adduct. An experiment in which nine consecutive isolation and activation steps (MS'O) are used to convert the [ 2M -HI + adduct, C,,H:, , to C32Hz' exemplifies the intriguing ion chemistry and the stability of the carbon skeleton of the adduct ions.

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“…The dominant pathway of the former is loss of a neutral fragment of 58 amu, neutral acetone, and this result is consistent with a proton bridged dimer structure 11. In contrast, the dominant pathway observed in protonated diacetone alcohol is the loss of water, a known reaction of protonated ketones (6,7). The ion of mlz 43 from the CID of this latter ion may be due to loss of a neutral fragment of 74 amu, presumably t-butanol, or via losses of acetone and methane or losses of isobutene and water.…”

Section: Mlz 117mentioning

confidence: 99%

An investigation of the structures of isomeric ions derived from acetone, diacetone alcohol, and mesityl oxide

March¹,

Young²

1988

Can. J. Chem.

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investigation of the structures of isomeric ions derived from acetone, diacetone alcohol, and mesityl oxide. Can. J. Chem. 66, 591 (1988). An investigation of the structures of isomeric ions formed in ion/molecule reactions occurring in 2-propanone (acetone), 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol), and 4-methyl-3-penten-2-one (mesityl oxide) has been performed using a hybrid mass spectrometer of reversed geometry. Ions of mlz 1 17, which have been observed as products of ion/molecule reactions in acetone and in diacetone alcohol, may have a single structure if an aldol type condensation reaction occurs under acidic conditions in the gas phase; however, high energy collision induced dissociation (CID) results proved the two ions to be isomeric only.Dehydration of the mlz 1 17 ions produced a species of mlz 99 which, in the case of diacetone alcohol, may have the structure of protonated mesityl oxide. That the mlz 99 ion formed was unique to each system was demonstrated by high energy CID and kinetic energy release (KER) spectrometry. In the acetone system, CID results suggested that rnlz 99 was an ion-dipole complex of c~H:(cH~)~co; this hypothesis was tested by clustering C~H: with (CD3)?C0 and comparison of its CID results with those obtained above. In the case of mlz 99 derived from diacetone alcohol or mesityl oxide, the neutral lost via metastable decomposition in the second field-free region was found to be C4Hs, presumably 2-methyl propene. While the ion of mlz 99 may also eliminate methane to yield a species of mlz 83, the dominant metastable elimination from this ion is carbon monoxide rather than ethene as shown by collision induced dissociative ionization (CIDI). The ions of mlz 83 observed in the two systems exhibit very similar CID spectra; however, a small variation in the yield of products of mlz 41 and 43 suggests two structures for the ion derived from diacetone alcohol, one of which is identical to that seen in mesityl oxide. RAYMOND EVANS MARCH et ALEXANDER BALDWIN YOUNG. An investigation of the structures of isomeric ions derived fromacetone, diacetone alcohol, and mesityl oxide. Can. J. Chem. 66, 591 (1988). Utilisant un spectromktre de masse de gComCtrie inversee, on a Ctudie les structures des ions isomkres qui se foment au cours des rkactions molCculaires se produisant dans la propanone-2 (acktone), I'hydroxy-4 methyl-4 pentanone-2 (diacktone alcool) et la mCthyl-4 pentkne-3 one-2 (oxyde de mksityle). I1 est possible que les ions de mlz 117, qui sont observCs comme produits dans les rkactions ionlmolCcules de I'acCtone et du diacCtone alcool, aient une structure unique si une reaction de type aldolique se produit dans des conditions acides, en phase gazeuse; toutefois, il est possible que des resultats de dissociations induites par des collisions B hautes Cnergies (DIC) prouvent que les produits ne sont que des isomkres.La deshydratation des ions de mlz 1 17 fournit une espkce de mlz 99 qui, dans le cas du diacCtone alcool, pourrait correspondre B un oxyde de mCsityle protonC. ...

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Fragmentation of even electron ions. Protonated ketones and ethers

Cited by 60 publications

References 35 publications

Gas‐phase dissociation of 1,4‐naphthoquinone derivative anions by electrospray ionization tandem mass spectrometry

Gas‐phase dissociation of 1,4‐naphthoquinone derivative anions by electrospray ionization tandem mass spectrometry

Ion—molecule chemistry of pyrene in an ion‐trap mass spectrometer

An investigation of the structures of isomeric ions derived from acetone, diacetone alcohol, and mesityl oxide

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