Ion–molecule reactions in the gas phase. Collision energy influence on the competitive SNi/SN2 orientation from adduct ions of epimeric 1,2-indanediols prepared by ammonia chemical ionization
✍ Scribed by C. Bourhis; M. C. Perlat; F. Fournier; J. C. Tabet
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 176 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0951-4198
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✦ Synopsis
Under chemical ionization (CI) conditions, cis and trans 1,2-indanediols mainly react with the NH 3 /NH 4 + system via a nucleophilic substitution process. In the CI source several mechanisms can occur yielding the substituted [M + NH 4 -H 2 O] + ions at m/z 150. Collisionally activated reaction (CAR) spectra provide additional information concerning the structure of selected low kinetic energy species. These ion-molecule reactions with methylamine are performed for [M + NH 4 -H 2 O] + ions in the collision cell of a triple quadrupole mass spectrometer. In this way, the nucleophilic substitution process is demonstrated to depend on the stereochemistry of the indanediol precursor. Stereospecific S N 2 and S N i pathways operate for the cis and trans derivatives, respectively. Such competitive orientations are explained by considering hydrogen bonds and the steric hindrance due to the homobenzylic group.