Role of hydrogen migration in the mechanism of acetic acid elimination from MH+ ions of acetates on chemical ionization and collision-induced dissociation
✍ Scribed by Kuzmenkov, I.; Etinger, A.; MandelbaumM, A.
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 121 KB
- Volume
- 34
- Category
- Article
- ISSN
- 1076-5174
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✦ Synopsis
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 beta- to the alpha-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 beta-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.