Computational study of bond dissociation enthalpies for lignin model compounds: β-5 Arylcoumaran

Abstract

The biopolymer lignin is a potential source of valuable chemicals. The β-5 linkage comprises ∼10% of the linkages in lignin. Density Functional Theory (DFT) was used to calculate the Cα–O and Cα–Cβ bond dissociation enthalpies (BDEs) for β-5 models with varied substituents, which are important for understanding initial lignin decomposition. The Cα–O (Cα–Cβ) BDEs were in the range of 40–44 (57–62)kcal/mol. The products resulting from either homolysis are bi-radicals with multi-determinant character in the singlet electronic state. Multiconfiguration self-consistent field (MCSCF) theory results were used to verify that unrestricted DFT and broken-symmetry DFT were sufficient to study these reactions.