Application Of Chloroperoxidase Modified Electrode In Catalytic Organic Synthesis

The biological enzyme catalysts are a class of non-toxic, cleanand efficient catalysts. The use of biological enzyme catalysts canreduce emissions of toxic and hazardous compounds and protectenvironmental, which is in full compliance with the requirements ofgreen chemistry.Due to its particular structure and catalytic activity inhalogenated olefins, epoxidation, hydroxylation, and sulfonatedoxidation of organic sulfur compounds Chloroperoxidase （CPO） hascaused widely attention. But H₂O₂can easily lead to enzymeinactivation and reducing the catalytic efficiency of enzymes.Therefore, many more moderate and efficient uses of CPO have beendeveloped. But these methods usually need complex reactors andspecial processes while CPO can not be used repeatedly. In this paperCPO was immobilized on the surface of glassy carbon （GC） electrode,electrochemical producing H₂O₂driving immobilized CPO to catalyticorganic reactions. By changing the way of modification the stability ofthe modified electrode was increased further, the total turnover andthe life of CPO modified electrode was obviously improved.Firstly,suspension of CPO in the Didodecyldimethylammonium bromide （DDAB）was dropped onto the surface of GCelectrode. After formation of thefilm at ambient temperature chitosan（Chi） was casted on the modifiedelectrode. SEM result of CPO modified electrode revealed island-likeaggregate structures which range from500to1000nm and averagefilm thickness was30nm estimated by AFM. Chi/CPO-DDAB/Nafion/GCmodified electrode gave a well-defined pair of quasi-reversible redoxpeaks with an electron transfer rate of2.3s-1. Integration of reductionpeak area from cyclic voltammetry of modified electrodes indicated52%of the CPO in the composite films were activated and contributed tothe electrochemical properties. The CPO modified electrode could effectively catalyze the reduction of O₂to H₂O₂which afforded agood foundation used for catalytic organicreactions.Chi/CPO-DDAB/Nafion/GC modified electrode as workingelectrode was successfully used for catalytic oxidation of cinnamylalcohol at-0.6V forming cinnamic aldehyde confirmed by H-NMR andIR. Further tests proved that the formation of the product of cinnamicaldehyde increased linearly with the increase of electrolysis time. Theconversion rate of cinnamic aldehyde was3.3μmol?h-1. The modifiedelectrode appeared a stable catalytic activity, the total conversion ofthe number was80500mol/mol CPO. Meanwhile,Chi/CPO-DDAB/Nafion/GC modified electrodes were also employedfor catalytic chlorination of vancomycin. The time of constant potentialelectrolysis determined the kind of finial products. Within the first hour,the main product was mono-chlorine vancomycin, then a new productof dichlorine vancomycin increased obviously with little change ofmono-chlorine vancomycin in4hours or less. Furtherly, the electrolysistime was delayed, the conversion amount of vancomycin has notbechanged. The stability of modified electrode was increased withcoated chitosan and the amount of dichlorine vancomycin was alsoenhanced. The catalytic chlorination system composed of CPOmodified electrode reached its highest efficiency at pH3.