甲紫精(MV)的电化学合成

Electro-synthesis of methyl viologen

N-甲基吡啶碘盐(MPI)经阴极电解还原可发生偶合反应得到1,1′-二甲基-1,1′,4,4′-四氢联二吡啶(DMTB)。此 DMTB 不用提取分离可随溶液经硝基苯氧化,用苦味酸成盐,再用盐酸转化而得到甲紫精(MV,即1,1′-二甲基-4,4′-联二吡啶氯盐)。整个过程条件温和,操作简单。电解还原偶合是在铅阴极上进行的。支持电解质为0.25N 氢氧化钠溶液,电极电势为-1.50±0.05V(SCE)。萃取剂为甲苯、苯或环已烷。净收率可达83.3%。

1,1′-Dimethyl-1,1′,4,4′-tetrahydrobipy-ridine(DMTB)was obtained through the cou-pling reaction after the cathodic reduction ofN-methylpyridinium iodide(MPI).TheDMTB thus obtained is neither extracted norseparated and can be oxidized directly withinthe solution by nitro-benzene,salted bypicric acid sad then transformed into methylviologen(MV,i.e.,1,1′-dimethyl-4,4′-bipyridyl chloride)by hydrochloric acid.Throughout the entire process,the conditionwas moderate and the operation was simple.The electro-reductive coupling reaction pro-gressed on the lead cathode,the supportingelectrolyte was 0.25N NaOH,the cathodepotential was-1.50±0.05V(SCE),theextracting agent may be toluene,benzene orcyclohexane and the net yield may reach83.3%.