Mass spectrometry benzyl cation

As another example, the tropylium ion [3 ], which is stabilized by virtue of the 67t electrons spread over a heptagonal sp hybridized carbon framework [Hiickel s (4n 4- 2)v rule with = 1], is also unstable in the gas phase. Its formation from toluene or the benzyl cation has been a long-standing problem in organic mass spectrometry, and the reaction mechanism and energetics have recently been exhaustively discussed (Lif-shitz, 1994). It was, however, isolated as the bromide salt by Doering and Knox (1954, 1957), and was the first non-benzenoid aromatic carbocation. 

Electron impact mass spectrometry studies of 1,3-di- and 1,2,3-tri-substituted imidazolines show ionization preferences depending on the substitution pattern (Scheme 23). Ions corresponding to R N were detected for all substrates (path 2). In 2-substituted 1,3-diarylimidazolidines, loss of substituents at C-2 ([M-R], path 3) is favored over the loss of hydrogen (path 4). In 1,2,3-trisubstituted compounds, azirinium ions (c, path 4A) were abundant, especially when R = aryl. 2-Phenylimidazolidines fragment to the characteristic tropylium ion (C7H7+, mjz 91). l-Aryl-3-benzylimidazolidines readily lose a benzyl group as radical or cation ([M-benzyl], path 1) <2000JHC57>. 

Mass Spectrometry The most common mass spectral fragmentation of alkylben-zene derivatives is the cleavage of a benzylic bond to give a resonance-stabilized benzylic cation. For example, in the mass spectrum of -butylbenzene (Figure 16-18),... 

Tandem mass spectrometry has been used to investigate the staeochemistry/structure of a series of monosaccharides and their boronate diesters. 2-Deoxy-D-nbo-ftiranosides have been employed to investigate ionization processes occurring in liquid-assisted SIMS (LSIMS). Several reports of metal-cationization in collision-induced decomposition in mass spectrometry of monosaccharide derivatives have been reported this year. A study of collision-induced decomposition of methyl 6-bromo-6-deoxy-a-E>-glucopyranoside metal-cationized by alkali metals or Agt, and of per-O-ace l- and pa -0-benzyl-a-l>-thioglycorides cationized by Li and Ag, have been described. Studies on alkyl per-0-acetyl-2-deoxy-2-halo-a- -mannopyransides have also been rqxmed. ... 

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