화학공학소재연구정보센터
Applied Catalysis A: General, Vol.555, 88-97, 2018
Selective control for the laccase-catalyzed synthesis of dimers from 2,6-dimethoxyphenol: Optimization of 3,3 ',5,5 '-tetramethoxy-biphenyl-4,4 '-diol synthesis using factorial design, and evaluation of its antioxidant action in biodiesel
The synthesis of transformed products from 2,6-dimethoxyphenol (2,6-DMP) can be selectively obtained through controlled oxidative coupling in laccase-catalyzed reactions, and the products formed are dependent upon the enzyme source, as well as, upon the reactions conditions applied. The laccase from Botryosphruria rhodina MAMB-05 was investigated for its ability to catalyze the oxidative transformation of 2,6-DMP. Studies conducted in aqueous medium at pH 3.0 and 6.5, for reaction times of 48, 96 and 144 h, led to the formation of three dimers (I, II, III) via carbon-carbon and carbon-oxygen coupling reactions depending upon the pH and reaction time. Dimer I was identified as 3,3',5,5'-tetramethoxydiphenylquinone by C-13 NMR, while dimer II was identified by H-1 NMR as 3,3',5,5'-tetramethoxybipheny1-4,4'-diol (TMBP). Dimer III was synthesized at pH 3.0 and was influenced by the reaction time (96h), and is predicted to be formed via carbon-oxygen coupling. The chemical structure of 111 (4-(2,6-dimethoxy-phenoxy)-2,6-dimethoxyphenol) was identified by ESI-Q-TOF HRMS. TMBP (II) was the only product obtained at pH 6.5 independent of the reaction times. TMBP synthesis at pH 6.5 was optimized by design-matrix using a three-factor Box-Behnken incomplete factorial-design that defined the parameters: 2,6-DMP concentration (2.6-3.4 mmol) laccase activity (1.35-3.38 U) and reaction time (120 h) to give a yield of 11.93 +/- 0.49%, which agreed with the mathematical model value of 12%. TMBP was evaluated as an antioxidant to stabilize biodiesel, and showed an efficacy similar to the commercial antioxidant standard, butyl hydroxytoluene, indicating that TMBP could serve as an alternative antioxidant to stabilize biodiesel.