Atmospheric Oxidation Mechanism of Phenol Initiated by OH Radical

作者：Xu Cui; Wang Liming^*

来源：Journal of Physical Chemistry A, 2013, 117(11): 2358-2364.

DOI：10.1021/jp308856b

• 2-nitrophenol
• Atmospheric oxidation
• DFT and ab initio
• Gas-phase oxidation mechanisms
• Orders of magnitude
• Ortho position
• Phenoxy radicals
• Ring closures

The gas-phase oxidation mechanism of phenol initiated by OH radical was investigated using DFT and ab initio calculations. The initiation of the reaction is dominated by OH addition to ortho-position, forming P2, which subsequently combines with O-2 at the ipso-position to form P2-1-OO adduct. A concerted HO2 elimination process from P2-1-OO was found to be much faster than the common ring closure to bicyclic intermediates. The HO2 elimination process from P2-1-OO forms 2-hydroxy-3,5-cyclohexadienone (HCH) as the main product and is also responsible for the experimental fact that the rate constants for reaction between P2 and O-2 are about 2 orders of magnitude higher than those between other aromatic-OH adducts and O-2. It was speculated that HCH would isomerize to catechol, which is thermodynamically more stable than HCH and was the experimentally observed main product, possibly through heterogeneous processes. Reaction of P2 with NO2 proceeded by addition to form P2-n-NO2 (n = 1, 3, 5), followed by HONO elimination from P2-1/3-NO2 to form catechol. The barriers for HONO elimination and catechol formation are below the separate reactants P2 and NO2, being consistent with the experimental observation of catechol in the absence of O-2, while H2O elimination from P2-1/3-NO2 to form 2-nitrophenol (2NP) is hindered by high barriers. The most likely pathway for 2NP is the reaction of phenoxy radical and NO2.

• 出版日期2013-3-21
• 单位华南理工大学