3,6-二氯吡啶甲酸的電解合成方法 畢業(yè)論文

摘  要
全鹵吡啶脫氯是鹵代吡啶類化合物合成的新嘗試， 本文在國內(nèi)外鹵代吡啶合成研究的基礎上，選擇了以電化學還原作為研究方向，以3,4,5,6-四氯吡啶甲酸、五氯吡啶、3,4,5,6-四氯-2-三氯甲基吡啶為原料，主要研究了其在銀和碳載銀電極上的還原行為。
本文第一章具體論述了三種原料脫氯后的目標產(chǎn)物的性質(zhì)、用途及制備方法，電極材料的應用等。為本實驗提供了研究背景。
第二章主要講述了本文所涉及的實驗內(nèi)容和方法。
第三章主要研究了3,4,5,6-四氯-2-三氯甲基吡啶在銀電極上的電還原行為。采用循環(huán)伏安法，計時電量法和恒電位電解法等電化學測試手段對3,4,5,6-四氯-2-三氯甲基吡啶的陰極還原行為，動力學特征及反應歷程進行了詳細的研究。
結(jié)果表明：銀電極對3,4,5,6-四氯-2-三氯甲基吡啶的電還原脫氯具有很高的電催化活性；3,4,5,6-四氯-2-三氯甲基吡啶在銀電極上的還原是由擴散所控制的電化學-化學過程；3,4,5,6-四氯-2-三氯甲基吡啶在純乙腈、乙腈/水混合溶液、N,N-二甲基甲酰胺、乙醇中都能被還原；恒電位電解實驗表明還原產(chǎn)物主要為脫氯加氫的產(chǎn)物，低電位時副產(chǎn)物較少，其中含水溶劑中可主要生成目標產(chǎn)物3,4,5,6-四氯-2-二氯甲基吡啶，副產(chǎn)物較少，純乙腈溶液中副反應較多；通過計時電量法求得3,4,5,6-四氯-2-三氯甲基吡啶在乙腈:水=5:1的混合溶劑中的擴散系數(shù)為D=2.7×10-5 cm2/s。
第四章主要研究了碳載銀的制備及其電催化性能。分析了不同功能離子預吸附、銀離子濃度等因素對碳載銀制備的影響；將碳載銀制成粉末微電極，采用循環(huán)伏安法測試其對3,4,5,6-四氯吡啶甲酸、五氯吡啶、3,4,5,6-四氯-2-三氯甲基吡啶的電催化性能。
結(jié)果表明：利用功能離子預吸附的方法能有效將銀分散在碳粉上，功能離子預吸附后分散效果及載銀量均好于直接吸附，功能離子分散能力大小順序為：Cl-﹤Br-﹤I-；銀離子濃度并非越高效果越好， 50~500mg/L催化效果隨銀離子濃度升高而增大，在1000mg/L時催化效果下降；碳載銀電極的電化學測試結(jié)果表明其對3,4,5,6-四氯吡啶甲酸、五氯吡啶、七氯吡啶的脫氯還原中電化學步驟相對其他步驟較快，有催化作用，且銀的粒徑越小，催化效果越好；
關鍵詞：3,4,5,6-四氯吡啶甲酸，五氯吡啶，3,4,5,6-四氯-2-三氯甲基吡啶，銀電極，碳載銀電極

Abstract
Dechlorination of entire halide pyridines pyridine is a new attempt for halogenated pyridines synthesized. Based on the research and development of synthesis of halogenated pyridines the paper chose the electrochemical reduction as a research direction, and to 3,4,5,6–tetrachloropicolinic acid, pentachloropyridine, 3,4,5,6-tetrachloro-2-trichloromethylpyridine for raw materials, the reduction behavior on  silver and carbon -containing silver electrode was mainly studied.
    ChapterI discussed the character, use and synthesis of 3,6–dichloropicolinic acid, 2,3,4,5-tetrachloropyridine, 3,4,5,6-tetrachloro-2-dichloromethylpyridine which were production of dechlorination of the three raw materials, the electrode materials applications were also disscussed. Provide background for the research.
Chapter II focuses on the experiment contents and methods.
In chapter III, electrochemical reduction behavior of 3,4,5,6-tetrachloro-2-trichloromethylpyridine on silver electrode was disscussed. The cathodic reduction behavior, the reaction kinetics and course of 3,4,5,6-tetrachloro-2-trichloromethylpyridine were carried out a detailed study by cyclic voltammetry, chronocoulometry and potential-controlled electrolysis.
The results showed that: silver electrode had a high electro-catalytic activity to 3,4,5,6-tetrachloro-2-trichloromethylpyridine; the reduction of 3,4,5,6-tetrachloro-2-trichloromethylpyridine on silver electrode was a diffusion-controlled irreversible process; the process was an EC (electrochemistry-chemistry) process; 3,4,5,6-tetrachloro-2-trichloromethylpyridine in pure acetonitrile, acetonitrile / water mixture solution, N, N-dimethylformamide, ethanol can be reduct; Potential-controlled electrolysis experiments showed that the main product were dechlorination and hydrogenation products, less byproducts had been produced at low potential; The byproducts can be reduced in the solvent containing water. The diffusion coefficient of 3,4,5,6-tetrachloro-2-trichloro methylpyridine in the mixed solvent which were acetonitrile: water = 5:1 was find out by chronocoulometry. D = 2.7 × 10-5 cm2 / s.
The major studies of Chapter IV were preparation methods of carbon containing silver, and its catalytic properties. It was analyzed that the effection on the preparation of carbon contained silver of different function ions of pre-adsorption, and silver ion concentration; and it was made of powder microelectrode testing electro-catalytic properties of 3,4,5,6-tetrachloropicolinic acid, pentachloropyridine, 3,4,5,6- tetrachloro-2-trichloromethylpyridine by cyclic voltammetry.
The results show that: use of functional ions pre-adsorption method can be effectively dispersed the silver, the order of decentralized capacity of functional ions: Cl-<Br- <I-; The concentration of silver ion is not the higher the better, and when the concentration were 50~500mg/L, catalytic effect increase with silver ion concentration increased but reduced at 1000mg/L. Carbon containing silver electrode electrochemical test results demonstrate that in the dechlorination of 3,4,5,6– tetrachloropicolinic acid, pentachloropyridine, 3,4,5,6- tetrachloro-2-trichloro methylpyridine, electrochemical reduction steps were faster than other steps, and the smaller the particle size of silver, better catalytic effect.
key words: silver electrode, carbon contain silver electrode, 3,4,5,6–tetrachloropicolinic acid, pentachloropyridine, 3,4,5,6-tetrachloro-2-trichloromethylpyridine,