title: Formation of dibenzofuran, dibenzo-p-dioxin and their hydroxylated derivatives from catechol.
abstract: We present, in this study, mechanistic and kinetic accounts of the formation of dibenzofuran (DF), dibenzo-p-dioxin (DD) and their hydroxylated derivatives (OHs-DF/OHs-DD) from the catechol (CT) molecule, as a model compound for phenolic constituents in biomass. Self-condensation of two CT molecules produces predominantly a DD molecule via open- and closed-shell corridors. Coupling modes involving the o-semiquinone radical and the CT molecule (o-SQ/CT) generate two direct structural blocks for the formation of OHs-DF/OHs-DD structures, ether-type intermediates and di-keto moieties. The calculated reaction rate constants indicate that the fate of ether-type intermediates is to make hydroxylated diphenyl ethers rather than to undergo cyclisation reactions leading to the formation of preDF structures. Unimolecular loss of a H or OH moiety from a pivotal carbon in these hydroxylated diphenyl ethers then produces hydroxylated and non-hydroxylated DD molecules. Formation of OHs-DF initiated by o(C)-o(C) cross-linkages involving o-SQ/o-SQ and o-SQ/CT reactions incurs very similar reaction and activation enthalpies encountered in the formation of chlorinated DFs from chlorophenols.
authors.affiliation: School of Engineering and Information Technology, Murdoch University, Perth, Australia. M.Altarawneh@Murdoch.edu.au.
authors.forename: Mohammednoor
authors.initials: M
authors.lastname: Altarawneh
authors.forename: Bogdan Z
authors.initials: BZ
authors.lastname: Dlugogorski
mesh_terms: D001572:Benzofurans / Q000138:chemical synthesis / Q000737:chemistry*; D002396:Catechols / Q000737:chemistry*; D004147:Dioxins / Q000138:chemical synthesis / Q000737:chemistry*; D006900:Hydroxylation; D015394:Molecular Structure
chemical_list: D001572:Benzofurans; D002396:Catechols; D004147:Dioxins; C023614:dibenzofuran; C034221:catechol; C020887:dibenzo(1,4)dioxin