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- 저자 : Kulangiappar Kumarasamy (검색결과 1 건)
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Electrochemical bromination and oxidation of alkyl aromatic compounds by two-phase electrolysis
Raju Thasan,Kulangiappar Kumarasamy 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.3
A simple, regioselective, environmentally clean and economical method for the preparation of side chain/ring brominated aromatic compounds is reported in 70-98% yield by an electrochemical method using two phase electrolysistechnique. Electrochemical reactions were carried out using aqueous 25-50 wt% sodium bromide containingcatalytic amount (5 wt%) of hydrobromic acid as an aqueous phase and chloroform containing alkyl aromatic compoundsas an organic phase, at a temperature of 0-30 oC in an undivided cell. The same two-phase electrolytic system can beused for the oxidation of benzylic alcohols to the corresponding benzaldehydes in 80-94% yield without over oxidationto carboxylic acids. The advantage of this very mild procedure is a room temperature reaction used with an undividedcell. Excellent conversions are observed. After completion of alcohol oxidation the electrolyte can be reused for a numberof times, demonstrating “spent reagent” free electro organic reaction as an attractive one. In the case of side chain/ringbromination of alkyl aromatic compounds, the electrolyte can be reused after making up the concentration of the electrolytewith 47 wt% HBr solution. In some cases homogeneous electrolysis is applied, where the two-phase electrolysisdid not work. Styrene epoxidation and α-bromination of ketones underwent homogeneous electrolysis at room temperaturewithout any catalyst. The reaction was performed in CH3CN-water (3 : 2) using equimolar amount of NaBras an electrolyte to get 68% of styrene epoxide. Use of an ionic liquid 1-butyl 3-methyl imidazolium bromide (Bmim)Br, instead of NaBr improved the yield and current efficiency of styrene epoxide to 86%.
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