| Abstrakt: |
Oxidation of secondary alcohols (2-propanol, 2-butanol, and cyclohexanol) by dioxygen, catalyzed by Cu and o-phenanthroline complexes, in the presence of alkali, was studied. The conditions under which oxidative dehydrogenation of secondary alcohols result in fast formation of ketones as the only primary oxidation products were found. Bis-phenanthrolinates [Cu(phen)] are the active forms of the catalyst. The catalytic turnover number for complexes between copper( i) and o-phenanthroline is 1 to 2 s at room temperature. Kinetic regularities of the reaction are similar to those of the oxidation of alcohols in the presence of oxidases. The mechanism of the process is proposed, suggesting that the oxidation of secondary alcohols occurs via a concerted two-electron mechanism involving a stage of formation of the ternary complex [O...Cu(phen)...OCHRR]. It is significant for the oxidation mechanism that a hydrogen atom is transferred from the anionic form of a substrate to oxygen, which is confirmed by the value of the kinetic isotope effect k/ k = 2.1. [ABSTRACT FROM AUTHOR] |
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