Kinetic role of tert-amines in the osmium tetroxide catalyzed trimethylamine N-oxide dihydroxylation of cyclohexene
✍ Scribed by Ender Erdik; Didem Kâhya
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 165 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0538-8066
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✦ Synopsis
Effect of some tert-amines on the catalytic osmium tetroxide dihydroxylation of cyclohexene in aqueous tert-butyl alcohol has been investigated. All amines have been found to retard the catalysis greatly and beyond a definite concentration of amine, the rate reaches a minimal and remains constant. The oxidation of cyclohexene is inhibited by pyridine, 2,2Јbipyridyl, and DABCO with an inverse first-order dependence whereas inhibition by triphenylamine, N,N-diethylaniline, picoline, pyrazine, hexamethylenetetraamine, and TMEDA shows an inverse partial order dependence. The involvement of dioxomonoglycolatoosmium(VI) esters and their monoamine adducts in the rate determining oxidation step was established by the linear plots of 1/⌬k 2 vs. 1/[L] where ⌬k 2 is the decrease in the second-order rate constant in the presence of [L] concentration of tert-amine. The ligand-accelerated or ligand-decelerated catalysis of tert-amines in the catalytic osmium tetraoxide dihydroxylation of alkenes may vary depending on the secondary oxidant, on the alkene, and on the structure and concentration of the tert-amine.