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Gas phase intramolecular cyclisation reactions of ionized aromatic compounds in mass spectrometry

Shodhganga@INFLIBNET

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Field Value
 
Title Gas phase intramolecular cyclisation reactions of ionized aromatic compounds in mass spectrometry
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Contributor George, M
 
Subject ortho effect
Chemistry
cyclisation
mass spectrum
fast atom bombardment
mass spectrometry
Chemical ionization
Electrospray ionisation
collision-induced dissociation
Metastable ion
 
Description Five novel gas-phase cyclisation reactions of suitably substituted aromatic compounds upon protonation by fast atom bombardment (FAB), chemical ionization (CI) and electrospray ionisation (ESI) in mass spectrometry have been explored. The [M+H]+ ions of N- [2-(benzoyloxy) phenyl]-benzamide eliminates benzoic acid with concomitant cyclisation, producing protonated 2-phenylbenzoxazole. A novel electrophilic cyclisation utilizing the protonated nitro group as electrophile, followed by competitive eliminations of two OH radicals and H2O from the [M+H]+ ions of 2-nitrophenyl phenyl ether afford heterocyclic product ions. Analogous cyclization of protonated 2-nitro-N phenylaniline followed by eliminations of H2O and OH radical yield heterocyclic fragments. The protonated 2-nitrophenyl-phenyl sulfide also undergoes cyclisation in gas-phase analogous to 2-nitrophenyl-phenyl ether. In addition, a novel ortho effect of nitro group involving cyclisations due to oxygen transfers from the nitro group to the sulphur atom occurs in protonated 2-nitrophenyl phenyl sulfide which resulted in the expulsions of SO and SO2 loss. Moreover, the sulfide undergoes oxidation at the emitter electrode in the ESI source during ionization in acidic solution. The mechanisms proposed for each cyclisation was supported by high-resolution data, chemical substitution, deuterium-labeling, tandem mass spectrometry experiments and theoretical calculations by density functional theory.
References given chapters wise
 
Date 2013-01-28T04:47:53Z
2013-01-28T04:47:53Z
2013-01-28
n.d.
February, 2007
n.d.
 
Type Ph.D.
 
Identifier http://hdl.handle.net/10603/6773
 
Language English
 
Relation -
 
Rights university
 
Format 229p.
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None
 
Coverage Chemistry
 
Publisher Kottayam
Mahatma Gandhi University
School Of Chemical Sciences
 
Source INFLIBNET