Potassium permanganate oxidized some alkylarenes such as ethylbenzene (1), propylbenzene (2), diphenylmethane (3), cumene (4), 1-bromo-2-phenylethane (5), indane (6), tetraline (7), and fluorene (8) at the benzylic position to form the corresponding aromatic ketones under solventless reaction conditions. Under the assisstance of ultrasound and microwave irradiation, the reaction times were reduced remarkably without a decrease of the yield. Reaction factors including the molar ratio of substrates, KMnO4, CuSO4 5H2O, reaction time, microwave power were optimized to achieve the highest conversion yields and product selectivities. | Science & Technology Development, Vol 11, - 2008 EFFECTS OF ULTRASOUND AND MICROWAVE IRRADIATION ON THE GREEN OXIDATION OF ALKYLARENES BY KMnO 4/CuSO4 5H2O Luu Thi Xuan Thi (1), Fritz Duus(2), Le Ngoc Thach (1) (1)University of Natural Sciences, VNU-HCM (2)Roskilde University, Denmark (Manuscript Received on November 18 th, 2008, Manuscript Revised April 29th, 2008) ABSTRACT: Potassium permanganate oxidized some alkylarenes such as ethylbenzene (1), propylbenzene (2), diphenylmethane (3), cumene (4), 1-bromo-2-phenylethane (5), indane (6), tetraline (7), and fluorene (8) at the benzylic position to form the corresponding aromatic ketones under solventless reaction conditions. Under the assisstance of ultrasound and microwave irradiation, the reaction times were reduced remarkably without a decrease of the yield. Reaction factors including the molar ratio of substrates, KMnO4, CuSO4 5H2O, reaction time, microwave power were optimized to achieve the highest conversion yields and product selectivities. Key words: Alkylarene, oxidation, permanganate, copper sulfate pentahydrate, ultrasound, microwave. Aromatic ketones are important intermediate products for the procurement of perfumes, drugs, and pharmaceuticals. In recent years, the preparation of aromatic ketones by the oxidation of alkyl groups close to an aromatic ring has been investigated in order to replace former method based on the Friedel-Crafts reaction. Erosive and toxic waste produced by the Friedel-Crafts acylation reaction is a main reason for improvement in synthetic ways to aromatic ketones.[1] The oxidation reactions were performed under heterogeneous conditions by KMnO4 absorbed on CuSO4 5H2O,[2] Al2O3,[3] zeolite,[4] montmorilonite K10.[5] Recently, the solventless oxidations were performed by using dichromate ion absorbed on alumina,[6] or KMnO4 mixed with CuSO4 5H2O.[7,8] Solventless reaction is important in Green chemistry.[9-11] It prevents from problems of solvent such .
