Water Vapor Does Not Catalyze the Reaction between Methanol and OH Radicals. Issue 15 (6th March 2019)

• Record Type: Journal Article
• Authors: Chao, Wen; Jr‐Min Lin, Jim; Takahashi, Kaito; Tomas, Alexandre; Yu, Lu; Kajii, Yoshizumi; Batut, Sébastien; Schoemaecker, Coralie; Fittschen, Christa
• Is Part Of: Angewandte Chemie international edition. Volume 58:Issue 15(2019)
• Page Start: 5013
• Page End: 5017
• Publication Date: 2019-03-06
• Subjects: alcohols -- atmospheric chemistry -- fluorescence -- radical reactions -- reaction mechanisms; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201900711
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Recent reports [Jara‐Toro et al., Angew. Chem. Int. Ed .2017, 56, 2166 and PCCP 2018, 20, 27885] suggest that the rate coefficient of OH reactions with alcohols would increase by up to two times in going from dry to high humidity. This finding would have an impact on the budget of alcohols in the atmosphere and it may explain differences in measured and modeled methanol concentrations. The results were based on a relative technique carried out in a small Teflon bag, which might suffer from wall reactions. The effect was reinvestigated using a direct fluorescence probe of OH radicals, and no catalytic effect of H2 O could be found. Experiments in a Teflon bag were also carried out, but the results of Jara‐Toro et al. were not reproducible. Further theoretical calculations show that the water‐mediated reactions have negligible rates compared to the bare reaction and that even though water molecules can lower the barriers of reactions, they cannot make up for the entropy cost. Abstract : No influence : The reaction of OH radicals with CH3 OH is the major removal path for CH3 OH from the atmosphere. In recent work, it was found that this reaction is substantially catalyzed by water. By using direct methods, the influence of H2 O on the reaction was reinvestigated, and no measurable influence of H2 O on the rate coefficient was discovered. RH=relative humidity.