Issue 15, 2002

The reaction of NO2 with solid anthrarobin (1,2,10-trihydroxy-anthracene)

Abstract

Reactions of atmospheric oxidants with condensed organic materials are implicated in secondary processes of relevance to the radiation budget of the atmosphere and to its oxidation capacity. A solid film of anthrarobin (1,2,10-trihydroxyanthracene) was exposed to gaseous NO2 at concentrations in the ppb range at atmospheric pressure, temperatures between 283 and 313 K and relative humidity between 20 and 80%. Gaseous HONO was the main product evolving from the anthrarobin surface. The reaction probability based on gas-kinetic collisions ranging between 2 × 10−6 and 7 × 10−7 decreased with time due to consumption of reactive surface molecules. It also decreased as a function of the NO2 concentration, which is in agreement with a Langmuir–Hinshelwood type surface reaction. A Langmuir constant of 5 × 10−3 ppb−1 for the reversible adsorption and a surface reaction rate constant of about 10−20 cm2 s−1 was derived. The reaction rate increased with increasing temperature, and the corresponding activation energy for the overall process was +39 kJ mol−1. The effect of humidity was to increase the reaction rate but also to increase the apparent HONO output, which was clearly not due to a bulk effect. The results suggest that the primary reaction is an electron transfer process between a deprotonated hydroxy group (equivalent to a phenoxide ion) hydrolyzed on the surface in the presence of humidity and NO2 leading to a surface nitrite. The results provide evidence that the system investigated may be a model system for the reaction of NO2 with soot.

Article information

Article type
Paper
Submitted
15 Feb 2002
Accepted
22 Apr 2002
First published
18 Jun 2002

Phys. Chem. Chem. Phys., 2002,4, 3684-3690

The reaction of NO2 with solid anthrarobin (1,2,10-trihydroxy-anthracene)

F. Arens, L. Gutzwiller, H. W. Gäggeler and M. Ammann, Phys. Chem. Chem. Phys., 2002, 4, 3684 DOI: 10.1039/B201713J

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