Formic Acid Catalyzed Gas‐Phase Reaction of H₂O with SO₃ and the Reverse Reaction: A Theoretical Study

Abstract

The formic acid catalyzed gas-phase reaction between H(2)O and SO(3) and its reverse reaction are respectively investigated by means of quantum chemical calculations at the CCSD(T)//B3LYP/cc-pv(T+d)z and CCSD(T)//MP2/aug-cc-pv(T+d)z levels of theory. Remarkably, the activation energy relative to the reactants for the reaction of H(2)O with SO(3) is lowered through formic acid catalysis from 15.97 kcal mol(-1) to -15.12 and -14.83 kcal mol(-1) for the formed H(2)O⋅⋅⋅SO(3) complex plus HCOOH and the formed H(2)O⋅⋅⋅HCOOH complex plus SO(3), respectively, at the CCSD(T)//MP2/aug-cc-pv(T+d)z level. For the reverse reaction, the energy barrier for decomposition of sulfuric acid is reduced to -3.07 kcal mol(-1) from 35.82 kcal mol(-1) with the aid of formic acid. The results show that formic acid plays a strong catalytic role in facilitating the formation and decomposition of sulfuric acid. The rate constant of the SO(3)+H(2)O reaction with formic acid is 10(5) times greater than that of the corresponding reaction with water dimer. The calculated rate constant for the HCOOH+H(2)SO(4) reaction is about 10(-13) cm(3) molecule(-1) s(-1) in the temperature range 200-280 K. The results of the present investigation show that formic acid plays a crucial role in the cycle between SO(3) and H(2)SO(4) in atmospheric chemistry.

Theoretical Studies on Reactions of OH with H2SO4…NH3Complex and NH2with H2SO4in the Presence of Water

“…We explore whether ammonia can accelerate the OH + H 2 SO 4 reaction and a single water molecule can promote the NH 2 + H 2 SO 4 reaction. Some theoretical and experimental investigations have demonstrated that a single water molecule can affect the rate constants of gas‐phase reactions in the atmosphere . In addition, the competition mechanisms between OH + NH 3 and OH + H 2 SO 4 are also considered, which may be of great interest because previous investigations have demonstrated that the similar reaction mechanisms play an important role in the atmospheric oxidation of HNO 3 .…”

Hydrolysis of Ketene Catalyzed by Formic Acid: Modification of Reaction Mechanism, Energetics, and Kinetics with Organic Acid Catalysis

“…Previous work from our lab 32−34 as well as by others 31,35,36 has shown that organic acids can lower the barriers for certain hydrolysis reactions. However, to the best of our knowledge, there have been no computational studies investigating the hydrolysis of ketene in the gas phase aided by organic acids.…”

Effect of NH3 and HCOOH on the H2O2 + HO → HO2 + H2O reaction in the troposphere: competition between the one-step and stepwise mechanisms

“…It has been proved in previous investigations that HCOOH can decrease the energy signicantly for several atmospheric hydrogen abstraction reactions. [31][32][33][34][35][36][37] Thus, it is also necessary to study the possible catalytic effect of HCOOH on the H 2 O 2 + HO reaction.…”