Synthesis of charged phenyl radicals and biradicals by laser photolysis in a Fourier-transform ion cyclotron resonance mass spectrometer

Thoen, Kami K.; Perez, James; Ferra, Joseph J.; Kenttämaa, Hilkka I.

doi:10.1016/s1044-0305(98)00097-x

Cited by 15 publications

(19 citation statements)

References 19 publications

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“…2), is observed for m/z 149 ions generated by PD of 4Br3Me, 3Br4Me and 3I4Me, implying that each of these radical ion populations consist of only a single species. 50,51 The general agreement between k 2nd values for radical ions generated by PD View Article Online of 3Br4Me and 3I4Me suggests the identity of the radical formed by l = 266 nm photolysis is unaffected by the halogen substituent on the radical precursor. Rate coefficients for m/z 149 from PD of 3Br4Me and 4Br3Me reveal a slight, but reproducible, difference in reaction rate where the radical is at the 3-over the 4-position relative to the charge-tag, i.e., k 3Br4Me > k 4Br3Me .…”

Section: Charge-tagged 2-methylphenyl + Omentioning

confidence: 83%

Hydroxyl radical formation in the gas phase oxidation of distonic 2-methylphenyl radical cations

Prendergast

Cooper

Kirk

et al. 2013

Phys. Chem. Chem. Phys.

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The reactions of distonic 4-(N,N,N-trimethylammonium)-2-methylphenyl and 5-(N,N,Ntrimethylammonium)-2-methylphenyl radical cations (m/z 149) with O 2 are studied in the gas phase using ion-trap mass spectrometry. Photodissociation (PD) of halogenated precursors gives rise to the target distonic charge-tagged methylphenyl radical whereas collision-induced dissociation (CID) is found to produce unreactive radical ions. The PD generated distonic radicals, however, react rapidly with O2 to form [M + O2]•+ and [M + O2 -OH]•+ ions, detected at m/z 181 and m/z 164, respectively. Quantum chemical calculations using G3SX(MP3) and M06-2X theories are deployed to examine key decomposition pathways of the 5-(N,N,N-trimethylammonium)-2-methylphenylperoxyl radical and rationalise the observed product ions. The prevailing product mechanism involves a 1,5-H shift in the peroxyl radical forming a QOOH-type intermediate that subsequently eliminates •OH to yield charge-tagged 2-quinone methide. Our study suggests that the analogous process should occur for the neutral methylphenyl + O2 reaction, thus serving as a plausible source of •OH radicals in combustion environments. The prevailing product mechanism involves a 1,5-H shift in the peroxyl radical forming a QOOH-type intermediate that subsequently eliminates OH to yield charge-tagged 2-quinone methide. Our study suggests that the analogous process should occur for the neutral methylphenyl + O 2 reaction, thus serving as a plausible source of OH radicals in combustion environments.

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Section: Charge-tagged 2-methylphenyl + Omentioning

confidence: 83%

Hydroxyl radical formation in the gas phase oxidation of distonic 2-methylphenyl radical cations

Prendergast

Cooper

Kirk

et al. 2013

Phys. Chem. Chem. Phys.

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“…In the gas phase, the distonic ions were studied in a Finnigan Model 2001 FTMS dualcell 3 Tesla Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer by using literature methods [12, 17]. …”

Section: Methodsmentioning

confidence: 99%

Comparison of the Reactivity of the Three Distonic Isomers of the Pyridine Radical Cation Toward Tetrahydrofuran in Solution and in the Gas Phase

Widjaja

Jin

Nash

et al. 2013

J. Am. Soc. Mass Spectrom.

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The reactivity of the three distonic isomers of the pyridine radical cation toward tetrahydrofuran is compared in solution and in the gas phase. In solution, the distonic ions were generated by UV photolysis at 300 nm from iodo-precursors in acidic 50:50 tetrahydrofuran/water solutions. In the gas phase, the ions were generated by collisionally activated dissociation (CAD) of protonated iodo-precursors in an FT-ICR mass spectrometer, as described in the literature. The same major reaction, hydrogen atom abstraction, was observed in solution and in the gas phase. Attempts to cleave the iodine atom from the 2-iodopyridinium cation in the gas phase and in solution yielded the 2-pyridyl cation in addition to the desired 2-dehydropyridinium cation. In the gas phase, this ion was ejected prior to the examination of the desired ion’s chemical properties. This was not possible in solution. This study suggests that solvation effects are not significant for radical reactions of charged radicals. On the other hand, the even-electron ion studied, the 2-pyridyl cation, shows substantial solvation effects. For example, in solution, the 2-pyridyl cation forms a stable adduct with tetrahydrofuran, whereas in the gas phase, only addition/elimination reactions were observed.

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“…The photochemistry utilized to generate radicals by PD is substantially different from that employed in the standard UVPD experiment. Several bond types, including CI and CS bonds, are susceptible to direct fragmentation following the absorption of a UV photon 52. 53 Homolytic fragmentation in the excited state occurs to yield radical species directly (dotted curve in Figure 2).…”

Section: Applications In Proteomicsmentioning

confidence: 99%

Ultraviolet Photodissociation: Developments towards Applications for Mass‐Spectrometry‐Based Proteomics

Ly¹,

Julian²

2009

Angew Chem Int Ed

134

158

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Unraveling of all of the information contained in proteomes poses a tremendous chemical challenge, which is balanced by the promise of potentially transformational knowledge. Mass spectrometry offers an unprecedented arsenal of tools for diverse proteomic investigations. Recently, it was demonstrated that ultraviolet light can be utilized to initiate unique and potentially useful fragmentations in peptides and proteins. Either nonspecific dissociation or highly specific dissociation at engineered chromophoric sites is possible following photon absorption. The level of specificity and control over fragmentation in these experiments is greater than with other fragmentation methods. Novel techniques made possible by this technology are poised to make substantial contributions to the field of proteomics.

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Synthesis of charged phenyl radicals and biradicals by laser photolysis in a Fourier-transform ion cyclotron resonance mass spectrometer

Cited by 15 publications

References 19 publications

Hydroxyl radical formation in the gas phase oxidation of distonic 2-methylphenyl radical cations

Hydroxyl radical formation in the gas phase oxidation of distonic 2-methylphenyl radical cations

Comparison of the Reactivity of the Three Distonic Isomers of the Pyridine Radical Cation Toward Tetrahydrofuran in Solution and in the Gas Phase

Ultraviolet Photodissociation: Developments towards Applications for Mass‐Spectrometry‐Based Proteomics

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