Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/62588
Type: Artigo de periódico
Title: Direct assignment of positional isomers by mass spectrometry: ortho, meta and para acyl and amidyl anilines and phenols and derivatives
Author: da Rocha, LW
Sparrapan, R
Augusti, R
Eberlin, MN
Abstract: A direct MS/MS method for the ortho, meta or para configuration assignment of any single molecule that forms reference ions upon ionization and dissociation is demonstrated. Gas-phase structure diagnostic ion-molecule reactions with acetonitrile are shown to distinguish the isomeric 2-, 3- and 4-hydroxybenzoyl cations and the 2- from the 3- and 4-aminobenzoyl cations. These reference ions, which display indistinguishable 15 eV collision-induced dissociation product ion mass spectra, react with acetonitrile to yield characteristic ratios of product ions, most particularly for the 2-isomers. The reactivity of the 2-benzoyl cations is the most characteristic since the ortho configuration allows for [4(+) + 2] polar cycloaddition that yields relatively stable heterocycles in N-protonated forms. Distinction of the reference isomeric 2-, 3-and 4-hydroxy- and aminobenzoyl cations permits, therefore, partially or completely, direct 'MS-only' positional assignment of either ortho, meta or para configuration for any single molecule that forms such reference ions upon ionization and dissociation. This "class-universal" method for direct MS assignment of a single positional isomer should therefore be applicable to many members of the homologous series of isomeric ortho, meta and para acyl and amidyl anilines and phenols and derivatives. Such molecules dissociate, or are likely to dissociate, after or during ionization processes to form the reference and structurally diagnostic ortho, meta or para hydroxy- or aminobenzoyl cations. Copyright (C) 2004 John Wiley Sons, Ltd.
Subject: pentaquadrupole mass spectrometry
acylium ions
cyclization reactions
isomer distinction
ortho, meta and para structural assignment
Country: Inglaterra
Editor: John Wiley & Sons Ltd
Rights: fechado
Identifier DOI: 10.1002/jms.704
Date Issue: 2004
Appears in Collections:Unicamp - Artigos e Outros Documentos

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