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Intramolecular charge transfer in the gas phase: fragmentation of protonated sulfonamides in mass spectrometry.
J Org Chem. 2010 Jun 18; 75(12):4244-50.JO

Abstract

The fragmentation of protonated molecules (MH(+)) in mass spectrometry usually results in even-electron product ions, but the MH(+) ions of sulfonamides are different as they often produce dominant radical cations of the constituent amines. For a series of benzenesulfonamides of anilines that bear various substituents, we found that the sulfonamides are preferentially protonated at the nitrogen, which is different from the carboxylic amides. Upon N-protonation, the S-N bond dissociates spontaneously to produce an intermediate [sulfonyl cation/aniline] complex. Within the ion-neutral complex, charge transfer between the two partners occurs in the gas phase to give rise to the ionized anilines. A substantial energy barrier was found to govern the reaction, which is consistent with the outer-sphere electron transfer mechanism. This energy barrier prevents the charge transfer when a strong electron-withdrawing substituent is attached to the aniline moiety. In contrast, when the aniline bears an electron-donating group, charge transfer is still more favorable than the dissociation of the intermediate ion-neutral complex, in spite of the existence of the energy barrier, and therefore dominates. A correlation was observed between the intensities of the ionized anilines and the ionization energies of these anilines.

Authors+Show Affiliations

Department of Chemistry, Zhejiang University, 38 Zheda Road, Hangzhou, Zhejiang 310027, China.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

20481449

Citation

Hu, Nan, et al. "Intramolecular Charge Transfer in the Gas Phase: Fragmentation of Protonated Sulfonamides in Mass Spectrometry." The Journal of Organic Chemistry, vol. 75, no. 12, 2010, pp. 4244-50.
Hu N, Tu YP, Jiang K, et al. Intramolecular charge transfer in the gas phase: fragmentation of protonated sulfonamides in mass spectrometry. J Org Chem. 2010;75(12):4244-50.
Hu, N., Tu, Y. P., Jiang, K., & Pan, Y. (2010). Intramolecular charge transfer in the gas phase: fragmentation of protonated sulfonamides in mass spectrometry. The Journal of Organic Chemistry, 75(12), 4244-50. https://doi.org/10.1021/jo100761k
Hu N, et al. Intramolecular Charge Transfer in the Gas Phase: Fragmentation of Protonated Sulfonamides in Mass Spectrometry. J Org Chem. 2010 Jun 18;75(12):4244-50. PubMed PMID: 20481449.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Intramolecular charge transfer in the gas phase: fragmentation of protonated sulfonamides in mass spectrometry. AU - Hu,Nan, AU - Tu,Ya-Ping, AU - Jiang,Kezhi, AU - Pan,Yuanjiang, PY - 2010/5/21/entrez PY - 2010/5/21/pubmed PY - 2010/9/21/medline SP - 4244 EP - 50 JF - The Journal of organic chemistry JO - J Org Chem VL - 75 IS - 12 N2 - The fragmentation of protonated molecules (MH(+)) in mass spectrometry usually results in even-electron product ions, but the MH(+) ions of sulfonamides are different as they often produce dominant radical cations of the constituent amines. For a series of benzenesulfonamides of anilines that bear various substituents, we found that the sulfonamides are preferentially protonated at the nitrogen, which is different from the carboxylic amides. Upon N-protonation, the S-N bond dissociates spontaneously to produce an intermediate [sulfonyl cation/aniline] complex. Within the ion-neutral complex, charge transfer between the two partners occurs in the gas phase to give rise to the ionized anilines. A substantial energy barrier was found to govern the reaction, which is consistent with the outer-sphere electron transfer mechanism. This energy barrier prevents the charge transfer when a strong electron-withdrawing substituent is attached to the aniline moiety. In contrast, when the aniline bears an electron-donating group, charge transfer is still more favorable than the dissociation of the intermediate ion-neutral complex, in spite of the existence of the energy barrier, and therefore dominates. A correlation was observed between the intensities of the ionized anilines and the ionization energies of these anilines. SN - 1520-6904 UR - https://www.unboundmedicine.com/medline/citation/20481449/Intramolecular_charge_transfer_in_the_gas_phase:_fragmentation_of_protonated_sulfonamides_in_mass_spectrometry_ L2 - https://doi.org/10.1021/jo100761k DB - PRIME DP - Unbound Medicine ER -