Details
| Original language | English |
|---|---|
| Pages (from-to) | 422-431 |
| Number of pages | 10 |
| Journal | Journal of the American Society for Mass Spectrometry |
| Volume | 27 |
| Issue number | 3 |
| Early online date | 4 Dec 2015 |
| Publication status | Published - 1 Mar 2016 |
| Externally published | Yes |
Abstract
In a preceding work with dopant assisted-atmospheric pressure photoionization (DA-APPI), an abundant ion at [M + 77]+ was observed in the spectra of pyridine and quinoline with chlorobenzene dopant. This contribution aims to reveal the identity and route of formation of this species, and to systematically investigate structurally related analytes and dopants. Compounds containing N-, O-, and S-lone pairs were investigated with APPI in the presence of fluoro-, chloro-, bromo-, and iodobenzene dopants. Computational calculations on a density functional theory (DFT) level were carried out to study the reaction mechanism for pyridine and the different halobenzenes. The experimental and computational results indicated that the [M + 77]+ ion was formed by nucleophilic aromatic ipso-substitution between the halobenzene radical cation and nucleophilic analytes. The reaction was most efficient for N-heteroaromatic compounds, and it was weakened by sterical effects and enhanced by resonance stabilization. The reaction was most efficient with chloro-, bromo-, and iodobenzenes, whereas with fluorobenzene the reaction was scarcely observed. The calculated Gibbs free energies for the reaction between pyridine and the halobenzenes were shown to increase in the order I < Br < Cl < F. The reaction was found endergonic for fluorobenzene due to the strong C-F bonding, and exergonic for the other halobenzenes. For fluoro- and chlorobenzenes the reaction was shown to proceed through an intermediate state corresponding to [M + dopant]+, which was highly stable for fluorobenzene. For the bulkier bromine and iodine, this intermediate did not exist, but the halogens were shown to detach already during the approach by the nucleophile.
Keywords
- Atmospheric pressure photoionization, Dopant, Gas-phase ion/molecule reactions, ipso-substitution, Nucleophilic aromatic substitution
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Structural Biology
- Chemistry(all)
- Spectroscopy
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In: Journal of the American Society for Mass Spectrometry, Vol. 27, No. 3, 01.03.2016, p. 422-431.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Nucleophilic Aromatic Substitution between Halogenated Benzene Dopants and Nucleophiles in Atmospheric Pressure Photoionization
AU - Kauppila, Tiina J.
AU - Haack, Alexander
AU - Kroll, Kai
AU - Kersten, Hendrik
AU - Benter, Thorsten
PY - 2016/3/1
Y1 - 2016/3/1
N2 - In a preceding work with dopant assisted-atmospheric pressure photoionization (DA-APPI), an abundant ion at [M + 77]+ was observed in the spectra of pyridine and quinoline with chlorobenzene dopant. This contribution aims to reveal the identity and route of formation of this species, and to systematically investigate structurally related analytes and dopants. Compounds containing N-, O-, and S-lone pairs were investigated with APPI in the presence of fluoro-, chloro-, bromo-, and iodobenzene dopants. Computational calculations on a density functional theory (DFT) level were carried out to study the reaction mechanism for pyridine and the different halobenzenes. The experimental and computational results indicated that the [M + 77]+ ion was formed by nucleophilic aromatic ipso-substitution between the halobenzene radical cation and nucleophilic analytes. The reaction was most efficient for N-heteroaromatic compounds, and it was weakened by sterical effects and enhanced by resonance stabilization. The reaction was most efficient with chloro-, bromo-, and iodobenzenes, whereas with fluorobenzene the reaction was scarcely observed. The calculated Gibbs free energies for the reaction between pyridine and the halobenzenes were shown to increase in the order I < Br < Cl < F. The reaction was found endergonic for fluorobenzene due to the strong C-F bonding, and exergonic for the other halobenzenes. For fluoro- and chlorobenzenes the reaction was shown to proceed through an intermediate state corresponding to [M + dopant]+, which was highly stable for fluorobenzene. For the bulkier bromine and iodine, this intermediate did not exist, but the halogens were shown to detach already during the approach by the nucleophile.
AB - In a preceding work with dopant assisted-atmospheric pressure photoionization (DA-APPI), an abundant ion at [M + 77]+ was observed in the spectra of pyridine and quinoline with chlorobenzene dopant. This contribution aims to reveal the identity and route of formation of this species, and to systematically investigate structurally related analytes and dopants. Compounds containing N-, O-, and S-lone pairs were investigated with APPI in the presence of fluoro-, chloro-, bromo-, and iodobenzene dopants. Computational calculations on a density functional theory (DFT) level were carried out to study the reaction mechanism for pyridine and the different halobenzenes. The experimental and computational results indicated that the [M + 77]+ ion was formed by nucleophilic aromatic ipso-substitution between the halobenzene radical cation and nucleophilic analytes. The reaction was most efficient for N-heteroaromatic compounds, and it was weakened by sterical effects and enhanced by resonance stabilization. The reaction was most efficient with chloro-, bromo-, and iodobenzenes, whereas with fluorobenzene the reaction was scarcely observed. The calculated Gibbs free energies for the reaction between pyridine and the halobenzenes were shown to increase in the order I < Br < Cl < F. The reaction was found endergonic for fluorobenzene due to the strong C-F bonding, and exergonic for the other halobenzenes. For fluoro- and chlorobenzenes the reaction was shown to proceed through an intermediate state corresponding to [M + dopant]+, which was highly stable for fluorobenzene. For the bulkier bromine and iodine, this intermediate did not exist, but the halogens were shown to detach already during the approach by the nucleophile.
KW - Atmospheric pressure photoionization
KW - Dopant
KW - Gas-phase ion/molecule reactions
KW - ipso-substitution
KW - Nucleophilic aromatic substitution
UR - http://www.scopus.com/inward/record.url?scp=84958154841&partnerID=8YFLogxK
U2 - 10.1007/s13361-015-1315-7
DO - 10.1007/s13361-015-1315-7
M3 - Article
C2 - 26637323
AN - SCOPUS:84958154841
VL - 27
SP - 422
EP - 431
JO - Journal of the American Society for Mass Spectrometry
JF - Journal of the American Society for Mass Spectrometry
SN - 1044-0305
IS - 3
ER -