Reaction of the OH Radical with Furfural. Spectral and Kinetic Investigation by Pulse Radiolysis and by ab Initio and Semiempirical Methods

Abstract

The reaction between the OH radical and furfural and the first stages of the subsequent processes have been investigated in detail. The model proposed for the overall kinetics has been verified by means of linear and nonlinear fittings up to the millisecond range. The identification of the intermediates has been based on ab initio optimized production enthalpies, as well as on the comparison of semiempirically predicted electronic transitions with the spectra observed after pulse radiolysis. The radical attack produces a radical adduct to the ring in position 5, k = (4.7 ± 0.8) × 109 M-1 s-1, which in sequence undergoes first a β-cleavage, k = (4.7 ± 2.4) × 105 s-1, and then a 1−6 hydrogen transfer, k = (3.4 ± 1.3) × 104 s-1. The final decay to a very low absorbing molecule occurs through a second-order reaction, k = (3.0 ± 0.5) × 108 M-1 s-1.

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

“…The experimental ionisation energy values obtained by high-resolution He(I) photoelectron spectroscopy 16 are used to help tentatively assign the Rydberg series, with the proposed Rydberg structures being presented in Table VI. The peak positions, E n , have been tested using the Rydberg formula, E n = E i − R/(n − δ) 2 , where E i is the ionisation energy, n is the principal quantum number of the Rydberg orbital of energy E n , R is the Rydberg constant (13.61 eV), and δ is the quantum defect resulting from the penetration of the Rydberg orbital into the core. Regarding the ionisation from the ring orbitals, the lowest energy (6.215 eV) is tentatively assigned to the Rydberg transition (3s ← 4a ′′ ), with a quantum defect δ = 0.87, whereas the np, np Table VI).…”

“…1 Recent investigations have also identified furfural as a viable plant-derived biochemical alternative to petrochemicals, as a part of sustainable bio-refineries aimed at reducing pollution. [2][3][4][5] With no direct synthetic methods of production, 1 furfural is solely produced through the thermochemical pre-treatment of biomass. While it is desirable to increase the conversion efficiency of hemicellulose into furfural, from the view point of furfural as a commodity chemical, 1 its production within some bio-refineries is undesirable, as it can inhibit enzymes responsible for upconversion of pre-treated biomass.…”

The Gas Phase HO-Initiated Oxidation of Furan: A Theoretical Investigation on the Reaction Mechanism

“…Furan and its derivatives are aromatic, heterocyclic organic compounds that are emitted to the troposphere from several sources including biomass burning, combustion of fossil fuels, refuse, meet cooking processes [1][2][3][4][5], and are also formed by oxidation or photooxidation of hydrocarbons such as 1,3 butadiene, 1,3 pentadiene or isoprene [6][7][8][9][10][11]. They are therefore primary pollutants that are degraded into the atmosphere by the reactions with HO, O 3 , NO 3 or by Cl or Br radicals [12][13][14][15][16][17][18][19][20][21][22][23][24][25], and the reaction with hydroxyl radical are the main sink in daytime.…”

A kinetic, spectral and theoretical investigation on the role of oxygen in the radiolytic oxidation of a sorbityl cyclic acetal

“…The reaction of OH with SF and with furfural, one of its components, was clarified in our recent papers [1,7], in connection with the effect of controlled amounts of oxygen added to produce peroxyl species [6]. Peroxyl radicals were proven to decay undergoing both an intra-and inter-molecular rearrangement.…”