Acta Phys. -Chim. Sin. ›› 2013, Vol. 29 ›› Issue (09): 2041-2046.doi: 10.3866/PKU.WHXB201306282

• CATALYSIS AND SURFACE SCIENCE • Previous Articles     Next Articles

Selective Oxidation of 4-Methoxymandelic Acid Catalyzed by Mononucleonic and Binucleonic Metal Complexes

YU Wei-Feng, MENG Xiang-Guang, LIU Ying, LI Xiao-Hong   

  1. Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, P. R. China
  • Received:2013-04-26 Revised:2013-06-28 Published:2013-08-28
  • Contact: MENG Xiang-Guang E-mail:mengxgchem@163.com
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21073126, 21273156).

Abstract:

Three kinds of mononucleonic metal complexes of L1Cu, L1Co, and L1Mn (L1=N,N'-bis-(2-hydroxyethyl)-malondiamide), and three kinds of binucleonic metal complexes of L2Cu, L2Co, and L2Mn (L2= N,N'-bis{2-(2-hydroxyethylamino)ethyl}-malondiamide) were prepared. These complexes exhibited good catalytic performance for the selective oxidation of 4-methoxymandelic acid (4-MMA) by H2O2 in buffer solution, with >96% selectivity to anisaldehyde (AAD) and a small percentage to 4-methoxybenzoic acid (4-MBA). However, the reaction rates were quite different for these catalytic systems, in which the copper complex was the best candidate as the catalyst for the oxidation of 4-MMA. The binucleonic complexes displayed obviously better catalytic performance than the mononucleonic complexes. The effect of the applied buffers (tartaric acid (TA), H3O4, HAc) on the catalytic performance in terms of activities and selectivities for the oxidation of 4-MMA by H2O2 were investigated. The reaction kinetics of 4-MMA oxidation catalyzed by six complexes was studied in detail. The apparent first-order rate constants (kobs) were obtained in the pH range of 2.5 to 4.5. The pHeffect on the catalytic oxidation was discussed in this paper.

Key words: 4-Methoxymandelic acid, Metal complex, Selective oxidation, Decarboxylation, Lignin

MSC2000: 

  • O643