Ab initio mechanism study on the reaction of chlorine atom with formic acid

The potential energy surface (PES) for the reaction of Cl atom with HCOOH is predicted using ab initio molecular orbital calculation methods at UQCISD(T, full)/6-311 ++ G(3df,2p)//UMP2(full)/6-311+ G(d,p) level of theory with zero-point vibrational energy (ZFVE) correction. The calculated results show that the reaction mechanism of Cl atom with formic acid is a C-site hydrogen abstraction reaction from cis-HOC(H)O molecule by Cl atom with a 3.73 kJ/mol reaction barrier height, leading to the formation of cis-HOCO radical which will reacts with Cl atom or other molecules in such a reaction system. Because the reaction barrier height of O-site hydrogen abstraction reaction from cis-HOC(H)O molecule by Cl atom which leads to the formation of HCO₂ radical is 67.95 kJ/mol, it is a secondary reaction channel in experiment. This is in good agreement with the prediction based on the previous experiments.