Water Catalysis of the Reaction between Methanol and OH at 294 K and the Atmospheric Implications

• Published in: Angewandte Chemie International Edition 2017-02, Vol.56 (8), p.2166-2170
• Main Authors: Jara‐Toro, Rafael A., Hernández, Federico J., Taccone, Raúl A., Lane, Silvia I., Pino, Gustavo A.
• Format: Article
• Language: English
• Subjects: atmospheric chemistry; hydroxyl radicals; Physics; water catalysis
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201612151

The rate coefficient for the reaction CH3OH+OH was determined by means of a relative method in a simulation chamber under quasi‐real atmospheric conditions (294 K, 1 atm of air) and variable humidity or water concentration. Under these conditions, a quadratic dependence of the rate coefficient for the reaction CH3OH+OH on the water concentration was found. Thus the catalytic effect of water is not only important at low temperatures, but also at room temperature. The detailed mechanism responsible of the reaction acceleration is still unknown. However, this dependence should be included in the atmospheric global models since it is expected to be important in humid regions as in the tropics. Additionally, it could explain several differences regarding the global and local atmospheric concentration of methanol in tropical areas, for which many speculations about the sinks and sources of methanol have been reported. The rate coefficient of the oxidation reaction of CH3OH by the OH radical depends quadratically on the humidity. This dependence affects the tropospheric lifetime of CH3OH ranging from 14 days in dry regions as deserts to 4 days in humid areas as the tropics.