| Abstract: | 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, 2.2′-bipyridyl and DABCO with an inverse first-order dependence whereas inhibition by triphenylamine NN-diethylaniline, picoline pyrazine hexamethylenetetraamine and TMEDA shows an inverse partial order dependence. The inolvement of dioxomonoglycolatoosmium(VI) esters and their monoamine adducts in the rate determining oxidation step was established by the linear plots of 1/Δk2 vs. 1/L] where Δk2 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. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 359–366, 1997 |
