Open AccessDouble bond migration to methylidene positions during electron ionization mass spectrometry of branched monounsaturated fatty acid derivatives
Author(s) -
JeanFrançois Rontani,
Nathalie Zabeti,
Claude Aubert
Publication year - 2009
Publication title -
journal of the american society for mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.961
H-Index - 127
eISSN - 1879-1123
pISSN - 1044-0305
DOI - 10.1016/j.jasms.2009.07.020
Subject(s) - chemistry , trimethylsilyl , electron ionization , double bond , mass spectrometry , mass spectrum , methyl group , allylic rearrangement , bond cleavage , chemical ionization , branching (polymer chemistry) , deuterium , fatty acid , medicinal chemistry , ionization , ion , stereochemistry , organic chemistry , chromatography , group (periodic table) , catalysis , quantum mechanics , physics
Electron ionization mass spectra of several monounsaturated methyl-branched fatty acid methyl and trimethylsilyl esters were examined. These spectra exhibited some intensive fragment ions, whose formation could be explained after double-bond migration to methylidene position. This preferential migration (substantiated by deuterium labeling) acts significantly in the case of monounsaturated fatty acid methyl and trimethylsilyl esters possessing a methyl branch localized between the penultimate and the C(4) positions (relative to the ester group), whatever the position of the double-bond. Allylic cleavage and gamma-hydrogen rearrangement of the ionized methylidene group thus formed afforded very interesting fragment ions, which could be particularly useful to determine branching positions of monounsaturated methyl-branched fatty acid methyl and trimethylsilyl esters without additional treatment.