Products and mechanism of the Cl-initiated atmospheric oxidation of furan: A theoretical study

The products and mechanism of the reaction of Cl atoms with furan on the ground potential energy surface (PES) have been studied by high level quantum chemical methods. The PESs for the Cl + furan reaction in the presence of O2/CH3O2 have been constructed at the CCSD(T)/6-311+g(d,p) level of theory on the basis of the geometric parameters optimized at the MP2(full)/6-311+g(d,p) level of theory. The calculations indicate that the reaction of Cl atoms with furan proceeds mainly by initial addition of Cl atoms to the unsaturated carbon atoms of the furan ring, followed by the formation of two Cl–furan adducts IM1 and IM2 ( and ). Under atmospheric conditions, the Cl–furan adduct IM1 can react further with O2/CH3O2 to generate the major product P5 (5-chloro-2(5H)-furanone, ) and the secondary product P6 (butenedial, C(O)HCHCHC(O)H). The calculated results are consistent with the available experimental observations. Moreover, the additional product P5A (2-chloro-3(2H)-furanone, ) is also predicted.