Theoretical Study on Impact of Single Water Molecule on OH+O3 Reaction

Abstract

Quantum chemical calculations are performed to study the reactions of OH and ozone without and with water to estimate whether the single water molecule can decrease the energy barrier of the OH radical reaction with ozone. The calculated results demonstrate that the single water molecule can reduce the activated barrier of the naked OH+O 3 reaction with the value of about 4.18 kJ/mol. In addition, the transition state theory is carried out to determine whether the single water molecule could enhance the rate constant of the OH+O 3 reaction. The computed kinetic data indicate that the rate of the ozone reaction with the formed complexes between OH and water is much slower than that of the OH+O 3 reaction, whereas the rate constant of OH reaction with the formed H 2 O• • • O 3 complex is 2 times greater than that of the naked OH radical with ozone reaction. However, these processes in the atmosphere are not important because the reactions can not compete well with the naked reaction of OH with ozone under atmospheric condition.

Role of the (H2O)n (n = 1–3) cluster in the HO2 + HO → 3O2 + H2O reaction: mechanistic and kinetic studies

“…In fact, at first, 30% of HO 2 in the atmosphere will form HO 2 Á Á ÁH 2 O with water vapor at 298 K; 27 this indicates that HO 2 Á Á ÁH 2 O is an important form; moreover, in previous studies on HO 2 + SO 2 , 28 HO 2 + SO 3 , 29 HO 2 + H 2 COO, 30 HO 2 + HO 2 , 17,31 HO 2 + O 3 , 32 HO 2 + NO 2 , 33 HO 2 + ClO, 34 and HO 2 + HClO 35 reactions, water molecules were found to play an important role in enhancing the stability of pre-reactive complexes and reducing the apparent activation energies of the transition states. In addition, the concentration of the formed H 2 OÁ Á ÁHO complex has been reported to be 5.5 Â 10 4 molecule cm À3 in the troposphere, 36 and previous studies on the water-catalyzed reactions HO + HOCl, 37 HCOOH + HO, 38 HO + H 2 O 2 , 39 HCHO + HO, 40 HO + HCl, 41 HO + CH 3 SO 3 H, 42 HO + CY 2 XH (X = H, F, OH, or NH 2 , and Y = H, CH 3 or F), 43 and HO + O 3 44 demonstrate how a single water molecule can catalyze a radical-molecule reaction involving HO radical; thus, the reactivity of HOÁ Á ÁH 2 O should also be taken into account. In these contexts, the important impact of water vapor on the atmospheric processes of the HO 2 + HO reaction may be not negligible.…”

Theoretical Studies on Gas-Phase Reactions of Sulfuric Acid Catalyzed Hydrolysis of Formaldehyde and Formaldehyde with Sulfuric Acid and H2SO4···H2O Complex

“…In particular, the uptake of formaldehyde on the sulfuric acid films is reported, which has potential implication in the atmosphere. In addition, the reactions of formaldehyde with sulfuric acid and H 2 SO 4 ···H 2 O complex are considered herein because the single water molecule can affect the atmospheric reaction processes. − The single water molecule plays a crucial role in the CH 3 CHO + OH, , OH+HOCl, H 2 SO 4 + OH, HCOOH + OH, , and SO 3 + HO 2 reactions.…”