A hydrogen-atom transfer mechanism in the oxidation of alcohols by [FeO4]2− in aqueous solution. Issue 1 (6th December 2017)

• Record Type: Journal Article
• Authors: Xie, Jianhui; Lo, Po-Kam; Lam, Chow-Shing; Lau, Kai-Chung; Lau, Tai-Chu
• Is Part Of: Dalton transactions. Volume 47:Issue 1(2017)
• Page Start: 240
• Page End: 245
• Publication Date: 2017-12-06
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c7dt03830e
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The oxidation of alcohols by [FeO4 ] 2− in aqueous solution is found to proceed via a hydrogen atom transfer (HAT) mechanism based on deuterium isotope effects, correlation between rate constants and bond dissociation energies (BDEs) and DFT calculations. Abstract : The ferrate(vi ) ion, [FeO4 ] 2−, has attracted much interest in recent years because of its potential use as a green oxidant in organic synthesis and water treatment. Although there have been several reports on the use of ferrate(vi ) for the oxidation of alcohols to the corresponding carbonyl compounds, the mechanism remains unclear. In this work, the kinetics of the oxidation of a series of alcohols with α-C–H bond dissociation energies ranging from 81 to 95 kcal mol −1 have been studied by UV/Vis spectrophotometry. The reactions are first-order in both [FeO4 ] 2− and [alcohol]. The deuterium isotope effects for the oxidation of methanol/ d 4 -methanol, ethanol/ d 6 -ethanol and benzyl alcohol/ d 7 -benzyl alcohol are 18.0 ± 0.1, 4.1 ± 0.1 and 11.2 ± 0.1, respectively. A linear correlation is found between the second-order rate constants and the α-C–H bond dissociation energies (BDEs) of the alcohols, consistent with a hydrogen atom transfer (HAT) mechanism. The proposed HAT mechanism is supported by DFT calculations.