Water does not Catalyze the Reaction of OH Radicals with Ethanol
Recent publications suggested that water catalyzes the reaction of OH radicals with alcohols (R. A. Jara-Toro; F. J. Hernandez; R. A. Taccone; S. I. Lane; G. A. Pino. Angew. Chem. Int. Ed. 2017, 56, 2166 for methanol and R. A. Jara-Toro; F. J. Hernandez; M. d. l. A. Garavagno; R. A. Taccone; G. A. Pino. Phys. Chem. Chem. Phys. 2018, 20, 27885 for ethanol and n-propanol) and increases the rate constant by a factor of 2 between dry conditions and relative humidities of 90%. However, a recent work from our group (W. Chao; J. Jr-Min Lin; K. Takahashi; A. Tomas; L. Yu; Y. Kajii; S. Batut; C. Schoemaecker; C. Fittschen. Angew. Chem. Int. Ed. 2019, 58, 5013) found the contrary for the case of methanol. No explanation for the disagreement could be found. Such an increase in the rate constant with increasing humidity would have a strong impact on the atmospheric lifetime of alcohols, because high relative humidities are commonly found in tropical regions where photochemical activity is high. Here, we present new experiments on ethanol that enable us to resolve this disagreement. We show that increased heterogeneous oxidation with increasing humidity systematically biased the work of Jara-Toro et al. and corroborate that water does not catalyze the reaction of OH with alcohols.