Theoretical study on the detailed reaction mechanisms of carbonyl oxide with formic acid

The reaction mechanisms of carbonyl oxide with formic acid are investigated using the B3LYP/6-311G(d,p) and CBS-QB3 theoretical methods. The investigation encompasses the eight complexes formed between carbonyl oxide and formic acid, the initial transition states responsible for the formation of these transitory products including hydroxylated ozonide and hydroperoxymethyl formate, the cleavages of the transitory intermediates and the interconversion between the transitory products and between syn-formic acid anhydride and anti-formic acid anhydride. The calculated results predict that the binding energy of the most stable complex in the eight complexes is −11.0 kcal/mol, which indicates that the formed pre-complexes are of special important for the reaction carbonyl oxide with formic acid. In addition, the barrier heights of the transition states that lead to the hydroxylated ozonide and hydroperoxymethyl formate are −0.5 kcal/mol, −1.3 kcal/mol, respectively, at the CBS-QB3 level of theory, which shows that the two reaction channels contribute to the transitory product formation. In addition, under some circumstances, the cleavages of transitory products result in the formation of the anti-formic acid anhydride, which is in well agreement with experimental predictions. It is noted that splits of hydroxylated ozonide are responsible for the formation of formic acid.