The addition reactions of NO(3) to limonene have been investigated using ab initio methods. Six different possibilities for NO(3) addition to the double bonds, which correspond to the two C-C double bonds (endocyclic or exocyclic) have been considered. The negative activation energies for the addition of NO(3) to limonene are calculated and the energies of NO(3)-limonene radical adducts are found to be 14.55 to 20.17 kcal mol-1 more stable than the separated NO(3) and limonene at the CCSD(T)/6-31G(d) + CF level. The results also indicate that the endocyclic addition reaction is more energetically favorable than the exocyclic one.
Keywords: ab initio; limonene; nitrate radical (NO3); volatile organic compounds.