CHEMICAL-MODEL OF OXIDASES - CU-I-CATALYZED OXIDATION OF SECONDARY ALCOHOLS BY DIOXYGEN

Oxidation of secondary alcohols (2-propanol, 2-butanol, and cyclohexan ol) by dioxygen, catalyzed by Cu-1 and o-phenanthroline complexes, in the presence of alkali, was studied. The conditions under which oxidat ive dehydrogenation of secondary alcohols result in fast formation of ketones as the only primary oxidation products were found. Bis-phenant hrolinates [Cu(phen)(2)](+) are the active forms of the catalyst. The catalytic turnover number for complexes between copper(I) and o-phenan throline is 1 to 2 s(-1) 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, sugges ting that the oxidation of secondary alcohols occurs via a concerted t wo-electron mechanism involving a stage of formation of the ternary co mplex [O-2...Cu(phen)(2)(+)...-OCHR(1)R(2)]. It is significant for the oxidation mechanism that a hydrogen atom is transferred from the anio nic form of a substrate to oxygen, which is confirmed by the value of the kinetic isotope effect k(H)/k(D) = 2.1.