Kinetics of oxidation and comproportionation reactions involving an oxammonium ion, benzyl alcohol and methyltrioxorhenium(VII)
✍ Scribed by Timothy H. Zauche; James H. Espenson
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 131 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0538-8066
No coin nor oath required. For personal study only.
✦ Synopsis
The reactions of 4-hydroxy-2,2,6,6-tetramethylpiperidinium N-oxide, an oxammonium ion abbreviated R 2 NO ϩ , have been studied. The previously unreported triflate salt was used in this study because the anions of the usual chloride and bromide salts can themselves be oxidized. Reactions between R 2 NO ϩ and alcohols produce ketones and aldehydes; the rate constant for PhCH 2 OH is 4.4 ϫ 10 Ϫ3 L mol Ϫ1 s Ϫ1 in acetonitrile at 298 K. The immediate product is the hydroxylamine, R 2 NOH, but its further comproportionation reaction with R 2 NO ϩ yields the stable piperidinyl oxyl radical, R 2 NO ⅐ . The rate constant of this reaction is 1.78 ϫ 10 3 L mol Ϫ1 s Ϫ1 at 298 K. The possibility of using R 2 NO ϩ and MTO as co-catalysts for the oxidation of alcohols was explored, but the competitive rates are such that the resultant is not particularly attractive.