title: Role of carbon-carbon phenyl migration in the pyrolysis mechanism of β-O-4 lignin model compounds: phenethyl phenyl ether and α-hydroxy phenethyl phenyl ether.
abstract: We investigate phenyl shift and subsequent β-scission reactions for PhCHXCH·OPh [X = H, OH], which are part of the pyrolysis mechanism of phenethyl phenyl ether (PPE) and α-hydroxy PPE. PPE and its derivatives are model compounds for the most common linkage in lignin, the β-O-4 linkage. We use density functional theory to locate transition states and equilibrium structures and kinetic Monte Carlo in combination with transition-state theory for kinetic simulations. Oxygen-carbon and carbon-carbon phenyl shift reactions proceed through cyclic intermediates with similar barriers. However, while subsequent β-scission of the oxygen-carbon shift products proceeds with virtually no barrier, the activation energy for β-scission of the carbon-carbon shift products exceeds 15 kcal/mol. We found that about 15% of β-radical conversion can be attributed to carbon-carbon shift for PPE and α-hydroxy PPE at 618 K. Whereas the oxygen-carbon shift reaction has been established as an integral part of the pyrolysis mechanism of PPE and its derivatives, participation of the carbon-carbon shift reaction has not been shown previously.
authors.affiliation: Joint Institute for Computational Sciences, The University of Tennessee, Oak Ridge, Tennessee 37831, USA. bestea@ornl.gov
authors.forename: Ariana
authors.initials: A
authors.lastname: Beste
authors.forename: A C
authors.initials: AC
authors.lastname: Buchanan
mesh_terms: D040761:Biomimetic Materials / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D004987:Ethers / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D007700:Kinetics; D008031:Lignin / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009010:Monte Carlo Method; D010647:Phenyl Ethers / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D004987:Ethers; D010647:Phenyl Ethers; D002244:Carbon; D006859:Hydrogen; D008031:Lignin