A Mn(IV)-Me4DTNE complex catalyzed oxidation of lignin model compounds with hydrogen peroxide

1-(3,4-dimethoxyphenyl)ethanol. 1-(3,4-dimethoxyphenyl)-1-propene (mixture of E- and Z-isomers) and E-1,2-diphenylethene were chosen as model compounds to investigate the reactivity of lignin toward hydrogen peroxide catalyzed by [L'Mn(IV)(mu-O)(3)Mn(IV)](ClO4)(2) where L' is 1,2-bis-(4,7-dimethyl-1,4,7-triazacyclonon-1-yl)ethane. All the model compounds investigated were readily oxidized to a significant extent by hydrogen peroxide when catalyzed by this complex. The reaction products were identified by GCMS, and the reaction kinetics was studied. Based on these results, the mechanisms of the reactions have been elucidated. The catalyst preferentially epoxidates C-C double bonds conjugated with aromatic moieties. The activation energy of the reactions was determined. (C) 1999 Elsevier Science B.V. All rights reserved.