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Role of hydrogen migration in the mechanism of acetic acid elimination from MH + ions of acetates on chemical ionization and collision‐induced dissociation
Author(s) -
Kuzmenkov I.,
Etinger A.,
MandelbaumM A.
Publication year - 1999
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(199908)34:8<797::aid-jms834>3.0.co;2-x
Subject(s) - chemistry , isobutane , acetic acid , dissociation (chemistry) , deuterium , kinetic isotope effect , carbocation , stereospecificity , collision induced dissociation , ion , medicinal chemistry , chemical ionization , photochemistry , ionization , organic chemistry , mass spectrometry , tandem mass spectrometry , catalysis , physics , quantum mechanics , chromatography
The elimination of acetic acid from the MH + ions of acetates of stereoisomeric 2‐methyl‐1‐cyclohexanols and 1‐hydroxy‐ trans ‐decalins exhibits a significant degree of stereospecificity under isobutane chemical ionization and collision‐induced dissociation (CID) conditions, resulting in more abundant [MH − AcOH] + ions in the cis ‐isomers 4c and 5tc than in their trans ‐counterparts 4t and 5tt. These findings suggest the involvement of a 1,2‐hydride shift from the β ‐ to the α ‐position in the course of the acetic acid elimination from the MH + ions of the above cis ‐acetates, resulting in tertiary carbocation structures. The proposed mechanism of the elimination is supported by a considerable deuterium isotope effect detected in β ‐deuterium‐labeled cis ‐2‐methyl‐1‐acetoxycyclohexane and by a CID study of the structures of the [MH − AcOH] + ions obtained from cis ‐ and trans ‐1,2‐diacetoxycyclohexanes. Copyright © 1999 John Wiley & Sons, Ltd.