Theoretical Studies on Reactions of the Stabilized H₂COO with HO₂ and the HO₂···H₂O Complex

Abstract

The reactions of H(2)COO with HO(2) and the HO(2)···H(2)O complex are studied by employing the high-level quantum chemical calculations with B3LYP and CCSD(T) theoretical methods, the conventional transition-state theory (CTST), and the Rice-Ramsperger-Kassel-Marcus (RRKM) with Eckart tunneling correction. The calculated results show that the proton transfer plus the addition reaction channel (TS1A) is preferable for the reaction of H(2)COO with HO(2) because the barriers are -10.8 and 1.6 kcal/mol relative to the free reactants and the prereactive complex, respectively, at the CCSD(T)/6-311++G(3df,2p)//B3LYP/6-311++G(d,p) level of theory. Furthermore, the rate constant via TS1A (2.23 × 10(-10) cm(3) molecule(-1) s(-1)) combined with the concentrations of the species in the atmosphere demonstrates that the HO(2) radical would be the dominant sink of H(2)COO in some areas, where the concentration of water is less than 10(17) molecules cm(-3). In addition, although the single water molecule would lower the activated barrier of TS1A from 1.0 to 0.1 kcal/mol with respect to the respective complexes, the rate constant is lower than that of the reaction of HO(2) with H(2)COO.

A kinetic study of the CH2OO Criegee intermediate self-reaction, reaction with SO2and unimolecular reaction using cavity ring-down spectroscopy

“…The relative contributions of these reactions to the value of ݇ ᇱ are discussed later. This value is consistent with the rate coefficient for CH2OO + HO2 of k = 2.23 x 10 -10 cm 3 molecule -1 s -1 calculated by Long et al 39 and is a factor of ~4 lower than the limiting capture rate for a barrierless reaction that we predict from estimated dipole moments for CH2OO and ICH2OO. The quality of the fit is good, with an adjusted R 2 value greater than 0.99, and the intercept was taken as the zero pressure limit value for ݇ ᇱ .…”

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

“…This method was used to compute the rate constant for low energy barriers in our previous studies. [30,75] Additionally, the rate constant of the reaction H 2 O with SO 3 in the presence of HCOOH was evaluated by using the pseudo-second order method proposed by Alvarez-Idaboy et al…”

Theoretical study of the OH-initiated atmospheric oxidation mechanism of perfluoro methyl vinyl ether, CF3OCFCF2

“…Catalytic HF elimination from CF 3 OH, a simpler analogue of CFOCF 2 OH, has been studied intensively theoretically, [23][24][25][26]28,45 and was found to be the key to understanding the rapid loss of CF 3 OH in many experiments, on a time scale of minutes to hours, while other experiments found very long lifetimes. [46][47][48][49][50] The CF 3 OH dissociation was found to be catalyzed by surfaces, by H 2 O and (H 2 O) 2 , as well as by aqueous particles; 23,25,45 our characterization of an H 2 O-catalysed HF-elimination from fluorinated glycolaldehyde with a barrier reduction of B30 kcal mol À1 strongly suggests that CFOCF 2 OH behaves similar to CF 3 OH in this respect. CF 3 OH dissociation is also self-catalysed by other CF 3 OH molecules, 24 as well as by HF and (HF) 2 molecules, 24,28 which allows for an autocatalysis mechanism.…”