Stereoisomeric fragment ions arising from decomposition of enol cation radicals of different internal energy content
作者： Thomas Weiske , Herman Halim , Helmut Schwarz
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摘要: The least-squares analysis of collisional activation mass spectra provides evidence that 1,1-dihydroxy-3-methylbutene cation radical (a) and 1-hydroxy-1-methoxy-3-methylbutene (c) (generated in a McLafferty-type rearrangement from 2-isopropyl-3-methylbutanoic acid its methyl ester) give rise to product ions b d, the stereochemistry which at double bond is determined by lifetime (internal energy) c, respectively. Decompositions c ion source yield predominantly less stable cis-configurated stereoisomers whereas dissociation longer lifetimes (lower internal results formation thermochemically more trans isomers d. A qualitative MNDO provided takes into account special features stereoelectronic control chemistry cleavage carboncarbon bond.
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