18570: Chemical Reactivity of C—C Bond Dissociations in Neutral and Cationic Model Lignin Compounds

Lignin is one of the most abundant naturally occurring aromatic biopolymer on earth. Efficient degradation of lignin is a timely and valuable task since it is a potential renewable source of fuels and chemicals. It is generally assumed that the catalysis of lignin results in cation radicals by a single electron transfer (SET) mechanism, which eventually undergoes C—C bond cleavage. However, owing to the complexity, little is known about the reactivity of neutral and radical cations and the nature of C—C bond dissociations. In this study, the structural and electronic features of neutral and radical cation lignin model compounds containing β-1 and β-O-4 linkages are investigated using abinitio/density functional theory. The calculated bond dissociation energies clearly indicate the selective C_α—C_β bond weakening upon electron delocalization and charge localization upon radical formation. Finally, the reactivity of these model compounds is addressed interms of possible influence of stereoselectivity and solvent effects.