Theoretical Study on the Gas Phase Reaction of Sulfuric Acid with Hydroxyl Radical in the Presence of Water

Abstract

The reactions of H2SO4 with the OH radical without water and with water are investigated employing the quantum chemical calculations at the B3LYP/6-311+G(2df,2p) and MP2/aug-cc-pv(T+d)z levels of theory, respectively. The calculated results show that the reaction of H2SO4 with OH and H2O is a very complex mechanism because of the formation of the prereactive complex prior to the transition state and product. There are two prereactive complexes with stabilization energies being -20.28 and -20.67 kcal/mol, respectively. In addition, the single water can lower the energy barriers of the hydrogen abstraction and the proton transfer to 7.51 and 6.37 kcal/mol, respectively from 13.79 and 8.82 kcal/mol with respect to the corresponding prereactive complex. The computed rate constants indicate that the water-assisted reaction of sulfuric acid with OH radical is of greater importance than the reaction of the naked sulfuric acid with the OH radical because the rate constant of the water-assisted process is about 10(3) faster than that of the reaction sulfuric acid with OH. Therefore, the conclusion is obtained that the water-assisted process plays an important role in the sink for the gaseous sulfuric acid in the clean area.

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

“…The process is similar to the reactions of OH with compounds in the presence of water. [28,30,34] Based on previous theoretical and experimental studies, [34,[71][72][73] the major features of the hydrogen-bonded complexes between formic acid and water are discussed here. Although there are three distinguishable complexes formed between formic acid and water, the most stable complex (M1) is shown in Figure 1 because of its contribution to the reaction mechanism.…”

“…Test calculations estimate the reliability of used methods and the uncertainty related to those energies. The geometrical structures of all reactants, prereactive complexes, transition states, and products were optimized by utilizing the hybrid density functional B3LYP method [39] with cc-pv(T+d)z [40] basis set and MP2 [41] approach with aug-cc-pv(T+d)z basis set, because their reliability and efficiency were confirmed by previous studies on reactions [13,17,18,30,42] and clusters [43][44][45][46][47][48][49] involving sulfuric acid. Moreover, it is also proven [50,51] that the cc-pv(T+d)z and augcc-pv(T+d)z basis sets can produce more accurate results for sulfur-containing compounds.…”

“…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…”

Will water act as a photocatalyst for cluster phase chemical reactions? Vibrational overtone-induced dehydration reaction of methanediol

“…30,31 Numerous other theoretical studies can also be cited that demonstrate the power of quantum chemistry methods to reveal TS barrier lowering for reactions in water clusters. [32][33][34][35][36][37] Our primary objective is to elucidate the role of water molecules as possible catalysts for photochemical reactions.…”

Theoretical Studies on the Single Water Molecule Effects on the Reaction of HOBr with OH·

“…例如水分子与大气中的硫酸分子形成氢键络合物, 有利 于硫酸中 OH 键泛频激发 [37] , 从而导致硫酸裂解为 SO 3 和水分子. 水分子加速 H 2 SO 4 ＋ OH• [38] , CH 3 CHO＋ OH• [39] 和 HCOOH＋OH•这些反应的进行 [12～40] . 此外, 水分子在固体表面反应中对反应机理的影响也有所报 道 [41,42] .…”