Using Fenton’s reagent (FeSO4 and H2O2 in water), the coupling of two radicals formed by hydrogen atom abstraction from the alpha-carbon of a ketone, in its keto form, results in the formation of a 1,4-diketone. However, the enol form predominates under the acidic Fenton conditions and thus, acetone produces acetonylacetone in low yield and acetophenone produces no 1,4-diketone. With acetophenone, the major reaction products derive from attack of the hydroxyl radical on the aromatic ring. A small percentage of these compounds, including phenol, are formed by ipso substitution. Identification of ipso substitution products from several substituted acetophenones and possible mechanisms for their formation will be presented. The cross coupling reaction of acetone and acetophenone produces a complex mixture containing 1,4-diketones, hydroxyacetophenones, ring coupling, and ipso substitution products. An increased acetone to acetophenone ratio, lower temperature, and higher pH produces a significantly higher percentage of 1,4-diketones. Possible mechanisms will be discussed.

Chemistry in water: Radical reactions of ketones using Fenton's reagent

254th National Meeting (2017)

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