Oxidative coupling of 2,6-dimethylphenol catalyzed by copper(II) complexes in aqueous solution

✍ Scribed by Ying Liu; Qin-Hui Pang; Xiang-Guang Meng; Fu-Rong Liu; Jian-Mei Li; Juan Du; Chang-Wei Hu

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 174 KB
• Volume: 118
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.32320

✦ Synopsis

The oxidative coupling reaction of 2,6dimethylphenol (DMP) with H 2 O 2 catalyzed by four copper(II) complexes was investigated in Tris-HNO 3 buffer solution at 25 C. The kinetics of formation of diphenoquinone (DPQ, 4-(3,5-dimethyl-4-oxo-2,5-cyclohexadienylidene)-2,6-dimethyl-2,5-cyclohexadienone) from DMP was studied in detail. The kinetic parameters k 2 and K m were obtained in the pH range of 6.0-9.0. The copper(II) complexes exhibited the optimal catalytic activity at around pH 7.0. The pH effect was reasonably explicated by the catalytic kinetic model suggested in this work. The catalytic mechanism was discussed. The deprotonized associ-ated radical LCu I (OH À )-OOH was suggested as the possible predominant species to oxidize DMP. The CAC and CAO coupling products were analyzed and the ratio of poly (2,6-dimethyl-1,4-phenylene ether) (PPE) to DPQ was also evaluated. Both in weak acidic (pH < 6.5) and in alkaline aqueous solution (pH > 8) were suitable to the CAO coupling reaction in our catalytic systems.