4-(2-Methoxyethyl) phenol (MEP) is an significant methoxypheolic compound, which has been shown to play an important role in the formation of secondary organic aerosols(SOA). The present work focuses on the gas-phase oxidation mechanism and kinetics of MEP and OH radical by the density functional theory (DFT). Energetically favourable reaction channels and feasible products were identified. The initial reactions of MEP with OH radical have two different channels: OH addition and H abstraction. Subsequent reaction schemes of main intermediates in the presence of O2 and NOx are investigated using quantum chemical methods at M06-2X/6-311++G(3df,2p)//M06-2X/6-311+G(d,p) level. Ketene, Phenyldiketones and nitrophenol compounds are demonstrated to be possible oxidation products. The total rate constant(1.69×10-11 cm3 molecule-1 s-1) and individual rate constant are calculated using the traditional transition state (TST) theory at 298K and 1atm. The lifetime of MEP is estimated to be 16.4 hours, which provides a comprehensive explanation for atmospheric oxidation pathway of MEP and shows MEP would be removed by OH radical in the atmosphere.

E,E-2,4-hexadienal is probably a precursor of secondary organic aerosol (SOA) and plays an important role in the atmospheric chemistry. Its main degradation routs are the reactions with OH, Cl, NO3 as well as photolysis. Atmospheric hydroxyl radical, as the most important oxidant, generally controls the removal of volatile organic compounds (VOCs) in the atmosphere. Thus, the quantum chemical calculations are used to investigate the reaction mechanism of E,E-2,4-hexadienal with hydroxyl radical, which would give better understanding for the main degradation products. The reaction paths of E,E-2,4-hexadienal with OH radical have been calculated accurately at the BMC-CCSD//M06-2X/6-311G (d, p) level at atmospheric pressure and room temperature. There are six hydrogen abstraction and four carbon addition paths at the first stages of this reaction. Due to the low energy barrier and reaction exotherm, the ten paths would contribute to the total reaction. Furthermore, the peroxy (RO2) and alkoxy (RO) radicals from the most important adduct IM1(CH3CHOHCHCH=CHCHO) would be formed in the atmospheric environment. The reaction mechanism of the peroxy radical (CH3CHOHCHO2CH=CHCHO) with NO, NO2, HO2, and self-reaction have been studied by using the same quantum chemical methods. And the reaction paths of alkoxy radical (CH3CHOHCHOCH=CHCHO) have been also originally studied. The subsequent reactions play a key role in the cycling of atmospheric radicals, production of ozone, and SOA formation. What’s more, the reaction mechanism of this study accords with the reported experimental observations.