Capture of Hydroxyl Radicals by Hydronium Cations in Water Microdroplets. Issue 33 (8th July 2022)

• Record Type: Journal Article
• Authors: Xing, Dong; Meng, Yifan; Yuan, Xu; Jin, Shuihui; Song, Xiaowei; Zare, Richard N.; Zhang, Xinxing
• Is Part Of: Angewandte Chemie international edition. Volume 61:Issue 33(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-07-08
• Subjects: Air–Water Interface -- Hydroxyl Radical -- Mass Spectrometry -- Microdroplet -- Olefin Oxidation; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.202207587
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Despite the high stability of bulk water, water microdroplets possess strikingly different properties, such as the presence of hydroxyl radicals (OH⋅) at the air–water interface. Previous studies exhibited the recombination of OH⋅ into H2 O2 molecules and the capture of OH⋅ by oxidizing other molecules. By spraying pure water microdroplets into a mass spectrometer, we detected OH⋅ in the form of (H4 O2 ) + that is essentially OH⋅−H3 O +, a hydroxyl radical combined with a hydronium cation through hydrogen bonding. We also successfully captured it with two OH⋅ scavengers, caffeine and melatonin, and key oxidation radical intermediates that bear important mechanistic information were seen. It is suggested that some previous reactions involving (H4 O2 ) + should be attributed to reactions with OH⋅−H3 O + rather than with the water dimer cation (H2 O−OH2 ) + . Abstract : The observation and capture of hydroxyl radicals spontaneously generated at the air–water interface of water microdroplets in the form of OH⋅−H3 O + is reported.