Exploration of the mechanism of the activation of ClONO{sub 2} by HCl in small water clusters using electronic structure methods

Journal Article · Thu May 04 04:00:00 UTC 2000 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp9932261· OSTI ID:20034422

McNamara, J P; Tresadern, G; Hillier, I H

High-level electronic structure calculations were used to study the mechanism of the reaction of ClONO{sub 2} with HCl in neutral water clusters containing one to five solvating water molecules. For the reaction between molecular HCl and ClONO{sub 2}, the barrier decreases from 42 kcal mol{sup {minus}1} (uncatalyzed) to essentially zero when catalyzed by only two water molecules, where the reaction products involve Cl{sub 2} and HONO{sub 2}. The calculations thus predict that the gas-phase reaction may be important in the stratospheric reactivation of ClONO{sub 2}. The reaction between ClONO{sub 2} and solvated H{sub 3}O{sup +}Cl{sup {minus}}, as on the polar stratospheric cloud (PSC) surface, was investigated with clusters involving up to seven water molecules. The ice-catalyzed reaction involves an ionic mechanism whereby charge transfer to ClONO{sub 2} from the attacking nucleophile leads to significant ionization along the Cl-ONO{sub 2} bond. The effect of the size of the first solvation shell of Cl{sup {minus}} is addressed by the calculations. In a cluster containing three waters and a five-water cluster structurally related to hexagonal ice, ClONO{sub 2} reacts spontaneously with HCl to yield Cl{sub 2}/HONO{sub 2} in the three-water reaction and Cl{sub 2}/H{sub 3}O{sup +}-NO{sub 3}{sup {minus}} in the five-water-catalyzed reaction. The calculations thus predict that the reaction of ClONO{sub 2} with HCl on PSC ice aerosols can proceed spontaneously via an ionic pathway.

• Research Organization: Univ. of Manchester (GB)
• OSTI ID: 20034422
• Journal Information: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 17 Vol. 104; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CHEMICAL REACTION KINETICS
CHLORINE NITRATES
CLOUDS
ELECTRONIC STRUCTURE
HYDROCHLORIC ACID
REACTION INTERMEDIATES
STRATOSPHERE