The reaction mechanism of NO3 + furan on the doublet potential energy surface has been studied at the CCSD(T)/6-311++ G(d, p) level based on the geometric parameters optimized at the B3LYP/6-311++ G(d, p) level of theory. The calculations reveal that the addition-elimination mechanism dominates the NO3 + furan reaction and the direct hydrogen abstraction pathways are negligible. The addition-elimination mechanism involves initial addition of NO3 to the furan ring to give furan-ONO2 intermediate (IN1). Initially formed intermediate IN1 has enough energy to undergo unimolecular rearrangement. The most energetically favorable channel is found to be the formation of 3H-furan-2-one via a simultaneous 1,2-H migration and the loss of NO2. (C) 2008 Elsevier B.V. All rights reserved.