Low temperature reaction of chlorine nitrate with water ice Formation of molecular nitric acid

Horn, Andrew B.; Sodeau, John R.; Roddis, Tristan B.; Williams, Neil

doi:10.1039/a801523f

Cited by 30 publications

(109 citation statements)

References 15 publications

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“…Rate constants : The main result of this study, summarized in Figure 7, is the extreme sensitivity of the reaction rate constant of chlorine nitrate hydrolysis on the amount of freely available water. This result is perfectly consistent with the experimental interpretation 18–23. In the case of the barrierless reaction in large water clusters the hydrolysis would supposedly even be collision limited.…”

Section: Resultssupporting

confidence: 91%

“…About 15 years ago upper limits for the rate constant of the homogeneous gas‐phase reaction have been determined and shown to be much too low to be important in the context of ozone depletion,11, 14 which explains why reduced ozone levels can be found mainly above the poles. After this discovery numerous laboratory experiments have focussed on determining the reaction probabilities γ for chlorine nitrate hydrolysis on different surfaces believed to mimick PSCs9, 15–17 at temperatures between 140 K and 200 K including ice, sulfuric acid solutions or nitric acid trihydrate 18–23. A common conclusion arising as a result to these experiments is the sensitivity of γ on equilibrium water vapour pressures, which are lowest for surfaces coated with acids such as nitric acid trihydrate.…”

Section: Introductionmentioning

confidence: 99%

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The Reaction Rate Constant of Chlorine Nitrate Hydrolysis

Loerting

Liedl

2001

Chem. Eur. J.

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The first-order rate constant for the decomposition of chlorine nitrate (ClONO2) by water in a cyclic 1:3 complex at stratospheric temperatures is shown to be close to the values for the hydrolysis rate coefficient of chlorine nitrate on an ice surface determined in the laboratory. On the other hand the rate constants calculated for the cyclic 1:1 and 1:2 complexes are much lower than the experimental results. From the mechanistic point of view the reaction is found to be similar to a SN2 mechanism and coupled with water-mediated proton transfer in accordance with the intriguing findings of Bianco and Hynes [R. Bianco, J. T. Hynes. J. Phys. Chem. A 1998, 102, 309-314]. The function of additional water molecules is to act as a catalyst, that is, to accelerate the hydrolysis process. Quantum-mechanical tunneling is negligible above 125 K in the 1:3 complex and above 175 K in the 1:2 complex. At temperatures below these limits all involved protons tunnel through the barrier at energies at least 5 kcalmol(-1) below the barrier-top in a concerted, but asynchronous manner.

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

The Reaction Rate Constant of Chlorine Nitrate Hydrolysis

Loerting

Liedl

2001

Chem. Eur. J.

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“…1270 cm -1 . These bands are consistent with the presence of hydrated nitric acid on the surface 37 and indicate that some of the ClONO 2 has been hydrated even at 90 K. We did not see any clear evidence for bands due to molecular HOCl, although the lower frequency bands are likely to be obscured by nitrate bands, while the band near 2700 cm -1 appears to be weak 11 and may be further broadened by the presence of molecular ClONO 2 . Oppliger et al 26 found that HOCl production in the gas phase was slow even at 180 K, suggesting that this resulted from slow decomposition of some precursor species, and it is possible that free HOCl does not form immediately during ClONO 2 hydration.…”

Section: Resultssupporting

confidence: 82%

Uptake and Reaction of ClONO₂on Water Ice and HCl Trihydrate at Low Temperatures

2002

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Chlorine nitrate adsorption kinetics and uptake have been measured on ordered ice and HCl trihydrate films at temperatures below 150 K. Reaction was followed using a thermal molecular beam, with mass spectrometric detection of gas-phase products and temperature-programmed desorption (TPD) and IR to identify adsorbed species. The sticking probability (S) on pure water ice is (0.98 ( 0.03) at 85 K and remains near unity for temperatures up to 145 K. Initially S is independent of the ClONO 2 uptake, indicating a trapping mechanism for reaction. A molecular state which desorbs near 120 K during TPD is identified as a precursor state and above this temperature molecular ClONO 2 is not stable on the surface and adsorption forms HOCl and nitric acid hydrate. On a clean ice surface the reaction probability starts to decrease after 0.1 monolayer of ClONO 2 has adsorbed, reaction ceasing (S < 5 × 10 -2 ) at an uptake of (0.25 ( 0.05) monolayer, independent of temperature. Reaction occurs even at low temperature, where the surface is immobile, indicating that ClONO 2 hydration can occur on the ice surface and does not require an extensive hydrate cage. The saturation stoichiometry is consistent with a surface covered with HOCl and an amorphous nitric acid trihydrate film. The initial reaction probability for ClONO 2 uptake onto pure HCl trihydrate films was similar, (0.98 ( 0.05) for temperatures between 85 and 145 K with some chlorine desorbing promptly into the gas phase even at 85 K. The uptake of ClONO 2 increases from 0.5 to ca. 1 monolayer above 125 K, the temperature at which HCl starts to transport into water ice films, reaction extending beyond the top layer of the HCl trihydrate surface.

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“…The structure of ClONO 2 in the reactant complex ( Figure 4a) is closely related to that of the free molecule (Table 1), with the charge distribution in the complexed ClONO 2 being essentially the same as that in the isolated molecule (Table 2) and with HCl being somewhat polarized with small charges of -0. 16 (Table 3), we studied the catalytic effect of the addition of a single water molecule to our model reaction system (Figure 4a) to yield a structure (Figure 5a) similar to that found previously in our study of the hydrolysis of ClONO 2 . 52 As for the uncatalyzed reaction, we examined the effect of different models of electron correlation and different basis sets on both the structures and energetics of the reaction.…”

Section: B Hcl‚(h 2 O) 3 and Hcl‚(h 2 O) 4 Recent Ab Initio And Montementioning

confidence: 92%

“…Furthermore, our cluster models confirm the experimental observations that at stratospherically relevant temperatures, the final reaction products contain the ionized form of nitric acid H 3 O + NO 3 -. 6,[13][14][15][16][17][18][19][20][21][22] Finally, in light of our calculations, the implications for stratospheric chemistry are discussed.…”

Section: Introductionmentioning

confidence: 97%

Exploration of the Mechanism of the Activation of ClONO₂by HCl in Small Water Clusters Using Electronic Structure Methods

2000

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

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Low temperature reaction of chlorine nitrate with water ice Formation of molecular nitric acid

Cited by 30 publications

References 15 publications

The Reaction Rate Constant of Chlorine Nitrate Hydrolysis

The Reaction Rate Constant of Chlorine Nitrate Hydrolysis

Uptake and Reaction of ClONO₂on Water Ice and HCl Trihydrate at Low Temperatures

Exploration of the Mechanism of the Activation of ClONO₂by HCl in Small Water Clusters Using Electronic Structure Methods

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Low temperature reaction of chlorine nitrate with water ice Formation of molecular nitric acid

Cited by 30 publications

References 15 publications

The Reaction Rate Constant of Chlorine Nitrate Hydrolysis

The Reaction Rate Constant of Chlorine Nitrate Hydrolysis

Uptake and Reaction of ClONO2on Water Ice and HCl Trihydrate at Low Temperatures

Exploration of the Mechanism of the Activation of ClONO2by HCl in Small Water Clusters Using Electronic Structure Methods

Contact Info

Product

Resources

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Uptake and Reaction of ClONO₂on Water Ice and HCl Trihydrate at Low Temperatures

Exploration of the Mechanism of the Activation of ClONO₂by HCl in Small Water Clusters Using Electronic Structure Methods