The pH dependence of photochemical reactions between methoxyphenols with Fe(III)-oxalates. (15th June 2023)

• Record Type: Journal Article
• Authors: Yang, Wangjin; Ma, Jiawei; Nan, Xiangli; Yan, Ran; Tang, Ning; Du, Tao; Han, Chong
• Is Part Of: Atmospheric environment. Volume 303(2023)
• Publication Date: 2023-06-15
• Subjects: Hydroxyl radical -- Metals-carboxylate complexes -- Methoxyphenols -- Light absorption -- Chemical composition; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2023.119749
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: The changes in optical properties and chemical compositions of four methoxyphenols, including guaiacol (GU), vanillin (VA), 4-nitroguaiacol (NGU) and 5-nitrovanillin (NVA) were investigated during the photochemical reaction with Fe(III)-oxalates. The reaction pathways of methoxyphenols with Fe(III)-oxalates were varied with solution pH. Four methoxyphenols were significantly decomposed by ·OH produced from Fe(III)-oxalates under irradiation at a solution pH of 3, followed by the formation of phenols, ketones and ethers. The degradation rate of methoxyphenols was closely correlated to electron-withdrawing groups on the benzene ring, such as NO2 and CHO groups. Under the neutral condition, the absorbance of methoxyphenols varied or remained unchanged, depending on the p K a values of methoxyphenols. The changes in the light absorption of VA and NGU solutions were contributed to the deprotonation of OH group in the presence of dissolved O2 . Highlights: The solution pH affected the reactivity of methoxyphenols to Fe-oxalates. Phenols, ketones and ethers were formed in reaction of guaiacol with Fe-oxalates. Reaction rate of methoxyphenols relied on the functional groups on benzene ring. Partial methoxyphenols was oxidized by dissolved O2 under neutral condition.