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 compound s to investigate the reactivity of lignin toward hydrogen peroxide catalyze d 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 catalyze d by this complex. The reaction products were identified by GCMS, and the r eaction 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 t he reactions was determined. (C) 1999 Elsevier Science B.V. All rights rese rved.