Oxidation with Tetrabutylammonium Permanganate Purple Benzene

OXIDATION WITH TETRABUTYLAMMONIUM PERMANGANATE (PURPLE BENZENE) 

Potassium permanganate (4.8 g, 0.03 mol) and 50 mL of water are vigorously stirred for 10 min, and the mixture is cooled in a water bath. Then 30 mL of benzene, 0.5 g (0.0016 mol) of tetrabutylammonium bromide, and 2 g (0.011 mol) of Irans-stilbene are added. The mixture is stirred for 3 h at room temperature and then treated sequentially with sodium bisulfite and acid. The benzene layer is separated, dried, and evaporated to give 2.49 g (92%) of benzoic acid. 

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Homogeneous oxidations are accomplished with tetrabutylammonium permanganate prepared by treating an aqueous solution of potassium permanganate with tetrabutylammonium bromide and isolating the crystalline precipitate [845, 599]. Tetrabutylammonium permanganate is soluble in dichloromethane, chloroform, acetone, and pyridine and sparingly soluble in benzene ( purple benzene ). 

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