Hydrolysis of Formyl Fluoride Catalyzed by Sulfuric Acid and Formic Acid in the Atmosphere

摘要

Formyl fluoride (HFCO) is an important atmospheric molecule, and its reaction with the OH radical is an important pathway when degradation of HFCO is considered in earth’s troposphere. Here, we study the hydrolysis of formyl fluoride (HFCO + H2O) with sulfuric acid (H2SO4) and formic acid (HCOOH) acting as catalysts by utilizing M06-2X, CCSD(T)-F12a, and conventional transitional state theory with Eckart tunneling to explore the atmospheric impact of the above-said hydrolysis reactions. Our calculated results show that H2SO4 has a remarkably catalytic role in the gas-phase hydrolysis of HFCO, as the energy barriers of the HFCO + H2O reaction are reduced from 39.22 and 41.19 to 0.26 and ?0.63 kcal/mol with respect to the separate reactants, respectively. In addition, we also find that H2SO4 can significantly accelerate the decomposition of FCH(OH)2 into hydrogen fluoride (HF) and HCOOH. This is because while the barrier height for the unimolecular decomposition of FCH(OH)2 into HF and HCOOH is 31.63 kcal/mol, the barrier height for the FCH(OH)2 + H2SO4 reaction is predicted to be ?5.99 kcal/mol with respect to separate reactants. Nevertheless, the comparative relative rate analysis shows that the reaction between HFCO and the OH radical is still the most dominant pathway when the tropospheric degradation of HFCO is taken into account and that the gas-phase hydrolysis of HFCO may only occur with the help of H2SO4 when the atmospheric concentration of OH is about 101 molecules cm–3 or less. Having an understanding from the present study that the gas-phase hydrolysis of HFCO in the presence of H2SO4 has very limited role possibly in the absence of sunlight, we also prefer here to emphasize that the HFCO + H2O + H2SO4 reaction may occur on the surface of secondary organic aerosols for the formation of HCOOH.