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Title: Gas phase intramolecular cyclisation reactions of ionized aromatic compounds in mass spectrometry
Researcher: Moolayil, Joseph T
Guide(s): George, M
Keywords: ortho effect
mass spectrum
fast atom bombardment
mass spectrometry
Chemical ionization
Electrospray ionisation
collision-induced dissociation
Metastable ion
Upload Date: 28-Jan-2013
University: Mahatma Gandhi University
Completed Date: February, 2007
Abstract: 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.
Pagination: 229p.
Appears in Departments:School Of Chemical Science

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01_title.pdfAttached File31.44 kBAdobe PDFView/Open
02_dedication.pdf33.01 kBAdobe PDFView/Open
03_declaration.pdf70.65 kBAdobe PDFView/Open
04_certificate.pdf50.3 kBAdobe PDFView/Open
05_acknowledgements.pdf78.66 kBAdobe PDFView/Open
06_abstract.pdf46.51 kBAdobe PDFView/Open
07_preface.pdf39.87 kBAdobe PDFView/Open
08_contents.pdf51.4 kBAdobe PDFView/Open
09_list of abbreviations.pdf37.94 kBAdobe PDFView/Open
10_list of tables.pdf54.13 kBAdobe PDFView/Open
11_list of figures.pdf111.32 kBAdobe PDFView/Open
12_chapter 1.pdf437.47 kBAdobe PDFView/Open
13_chapter 2.pdf613.57 kBAdobe PDFView/Open
14_chapter 3.pdf1 MBAdobe PDFView/Open
15_chapter 4.pdf707.31 kBAdobe PDFView/Open
16_chapter 5.pdf568.52 kBAdobe PDFView/Open
17_chapter 6.pdf58.8 kBAdobe PDFView/Open
18_summary.pdf86.05 kBAdobe PDFView/Open
19_list of publications.pdf44.48 kBAdobe PDFView/Open

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