experimental and computational investigation on the fragmentation behavior of enaminones in electrospray ionization mass spectrometry
The dissociation pathways of protonated enaminones with different substituents were investigated by electrospray ionization tandem mass spectrometry (ESI‐MS/MS) in positive ion mode. In mass spectrometry of the enaminones, ArCOCHCHN(CH₃)₂, the proton transfers from the thermodynamically favored...
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Published in | Journal of mass spectrometry. Vol. 45; no. 11; pp. 1291 - 1298 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Chichester, UK
John Wiley & Sons, Ltd
01.11.2010
Wiley |
Subjects | |
Online Access | Get full text |
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Summary: | The dissociation pathways of protonated enaminones with different substituents were investigated by electrospray ionization tandem mass spectrometry (ESI‐MS/MS) in positive ion mode. In mass spectrometry of the enaminones, ArCOCHCHN(CH₃)₂, the proton transfers from the thermodynamically favored site at the carbonyl oxygen to the dissociative protonation site at ipso‐position of the phenyl ring or the double bond carbon atom adjacent to the carbonyl leading to the loss of a benzene or elimination of C₄H₉N, respectively. And the hydrogendeuterium (H/D) exchange between the added proton and the proton of the phenyl ring via a 1,4‐H shift followed by hydrogen ring‐walk was witnessed by the D‐labeling experiments. The elemental compositions of all the ions were confirmed by ultrahigh resolution Fourier transform ion cyclotron resonance tandem mass spectrometry (FTICR‐MS/MS). The enaminones studied here were para‐monosubstituted on the phenyl ring and the electron‐donating groups were in favor of losing the benzene, whereas the electron‐attracting groups strongly favored the competing proton transfer reaction leading to the loss of C₄H₉N to form a benzoyl cation, Ar‐CO⁺. The abundance ratios of the two competitive product ions were relatively well‐correlated with the σp ⁺ substituent constants. The mechanisms of these reactions were further investigated by density functional theory (DFT) calculations. Copyright © 2010 John Wiley & Sons, Ltd. |
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Bibliography: | http://dx.doi.org/10.1002/jms.1812 ArticleID:JMS1812 ark:/67375/WNG-T5L3NK4B-F NSF of China - No. 20975092 National Ministry of Education of China - No. NCET-06-520 istex:29C353F39244183FC3A86955356845DB168991A2 Supporting Information ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2 |
ISSN: | 1076-5174 1096-9888 1096-9888 |
DOI: | 10.1002/jms.1812 |