【作者】 王欢；

【导师】 陆嘉星；

【作者基本信息】 华东师范大学 ， 物理化学， 2008， 博士

【摘要】 如今，随着人类对赖以生存的地球环境保护的重视，绿色化学的概念日益兴起。绿色化学，又称为环境友好化学，主要致力于不再使用有毒、有害的物质，不再产生废物；生产环境友好的产品；合理利用资源和能源，降低生产成本。绿色化学的原则之一是“原子经济性”，即最大限度地利用原料分子的每个原子，使之结合到目标分子中，达到零排放。有机电合成使用电子作为反应试剂，避免了其它还原剂或氧化剂的使用，环境友好，并完全符合“原子经济性”要求。与传统的有机合成方法相比，是一种绿色的合成技术。绿色化学的另一个原则是使用安全、环境友好的溶剂，以及温和的反应条件。具有蒸气压低，热稳定性高，溶解力强等优点的离子液体，已作为传统有机溶剂的替代品被广泛应用于化学的各个领域。更由于其高的导电率、宽的电化学窗口等特性，可以不用额外添加支持盐而直接应用于电化学研究，可谓是一种绿色的溶剂。CO₂是最主要的温室气体，将其固定利用不仅可以控制温室气体排放，减少环境污染，而且可以利用廉价而且丰富的C1资源合成重要的化工产品。由于CO₂是C的最高价氧化物，非常稳定，传统的活化固定方式都需要高温高压，不符合绿色化学的宗旨，而电化学方法恰好能够在温和的条件下对其进行固定。苯基丁二酸和腈基-苯基-丙酸等羧酸化合物是重要的药物中间体。其传统的合成方法通常需要使用危险的试剂、昂贵复杂的催化剂、高温高压的反应条件等。因而，急需找到一条新的，更为绿色化的合成路线。采用绿色的电合成方法，在温和的条件下，对温室气体CO₂进行固定，并合成重要的羧酸类化合物，具有很高的实际应用价值。而绿色溶剂——离子液体在该类研究中的使用，更是具有十分重要的创新意义。本论文研究的主要内容如下：（1）苯基丁二酸的电化学合成在常压CO₂气氛下，含0．1 mol L^-1 Et₄NBr的MeCN溶液中，选用廉价易得的钛、不锈钢、铜、镍等材料作为阴极对苯乙烯的电羧化反应进行研究。成功地合成了单一产物——苯基丁二酸，从而避免了复杂催化剂或昂贵Pt电极的使用，以及混合产物的分离。通过反应条件的优化，最高羧酸化产率可达86．1％。并运用循环伏安法研究了该电羧化反应的电化学行为，推得了反应机理。该工作首次选用廉价易得的电极材料实现了苯乙烯的电羧化，拓展了电羧化反应的电极选择范围。（2）肉桂酸乙酯的电化学还原和羧酸化在一室型电解池中，以MeCN为溶剂、Mg为牺牲阳极，研究了肉桂酸乙酯的电化学还原和电化学羧酸化反应。首先用循环伏安法研究了肉桂酸乙酯在MeCN中的电还原行为，探讨了扫描速度对行为的影响。结合恒电流电解得到产物的分析，推测了肉桂酸乙酯电还原的反应机理。然后在饱和CO₂的MeCN溶液中，运用恒电位电解法对肉桂酸乙酯进行电羧化，通过对反应条件的优化，得到最高78％的羧酸化产率。该工作探讨了其电还原的反应机理，并运用恒电位技术实现了肉桂酸乙酯的电化学羧酸化，对该类反应的深入研究具有重要的参考价值。（3）肉桂酸酯类的恒电流电羧化在一室型电解池中，以MeCN为溶剂、Mg为牺牲阳极，研究了肉桂酸酯类的恒电流羧酸化反应。首先以肉桂酸甲酯为模版化合物，考察了各个反应条件对恒电流羧酸化反应的影响，最高产率可达77．4％。然后把该反应扩展到其他肉桂酸酯类，得到了相应的羧酸化产物，产率在61．9％～78．9％范围内。接着运用循环伏安法探讨各个肉桂酸酯类物质的电化学行为。最后结合上述研究推测肉桂酸酯类的电羧化反应机理。本工作成功地运用操作更为简单方便的恒电流技术实现了肉桂酸酯类的电羧化反应。（4）肉桂腈的电化学还原和羧酸化在一室型电解池中，以MeCN为溶剂，Mg为牺牲阳极，研究了肉桂腈电化学羧酸化合成腈基-苯基-丙酸的反应。首先用循环伏安法研究肉桂腈在MeCN中的电化学行为，考察其在该体系中电还原的可行性。并运用恒电位电解技术探讨了不同电位下肉桂腈电还原的产物，结合循环伏安行为的模拟推得了其电还原的反应机理。然后在饱和CO₂的MeCN中，用恒电位法实现了肉桂腈的电羧化，并考察了各个反应条件对产率的影响。在最优化条件下，羧酸化总产率可达84．8％。本工作通过电羧化肉桂腈的方法合成了腈基-苯基-丙酸，为这种重要的化学中间体的合成提供了一种更为安全方便的合成方法。（5）活泼烯烃在离子液体中的电羧化在离子液体BMIMBF₄中研究了活泼烯烃的电化学羧酸化反应。先用循环伏安法探讨了活泼烯烃在玻碳电极上的电还原行为，证明其经历的是一个由扩散控制的不可逆还原过程。再用恒电流技术，在温和的条件下，一室型电解池中实现了活泼烯烃的电羧化反应，从而避免了易挥发、有毒溶剂，催化剂和支持盐的使用。反应最后得到了产率为35％～55％的单羧酸化产物。最后还考察了离子液体的回收利用可行性，发现至少可以重复使用5次且对电羧化产率几乎没有影响。这项工作首次实现了离子液体中的电羧化反应，为离子液体中固定CO₂提供了一种新的方法。（6）香豆素类化合物在离子液体BMIMBF₄中的电化学还原在离子液体BMIMBF₄中研究了香豆素的电化学还原反应。先用循环伏安法探讨了香豆素在玻碳电极上的电还原行为，并进一步考察了扫描速度、底物浓度和温度等对伏安行为的影响，证明该反应是一个受扩散控制的不可逆单电子还原过程。并运用计时电量法求得了香豆素在BMIMBF₄中的扩散系数。运用恒电位技术实现了香豆素在BMIMBF₄中的电化学二聚反应，并结合电化学行为推得了反应机理。另外还讨论了水和取代基团等对香豆素还原的影响。该工作首次实现了离子液体中碳碳双键的电还原二聚反应，为这类双键化合物的电还原提供了一条新的思路。（7）离子液体中Co（L）电催化氯苄与CO₂反应在离子液体中研究了CoL（钴希夫碱配合物）电催化氯苄与CO₂的反应。先用循环伏安法考察了CoL在离子液体中的电化学行为，得到一对由扩散控制的单电子可逆氧化还原峰。探讨了金属有机配合物配体和离子液体阴离子对该行为的影响，并求得相应的扩散系数。然后研究了离子液体中CoL对氯苄还原的催化作用，探讨了其催化机理，并求得了反应的动力学常数。最后进一步考察饱和CO₂的离子液体中，CoL对氯苄的催化还原反应，运用恒电位技术得到了氯苄的羰基化产物二苄基酮。该工作首次实现了离子液体中，CO₂的CoL电催化固定，为离子液体中固定CO₂提供了一种新的途径。（8）新型离子液体dialcarbs的合成和电化学性质以CO₂和二烷基胺为原料，合成了一类新型的离子液体dialcarbs，并对其各项电化学性质进行了研究。该类离子液体的黏度和电导率与常规的离子液体相当，与温度的关系符合Arrhenius方程，并由此求得了相应的活化能。根据Walden曲线推得，该类离子液体属于“subionic”liquids。循环伏安研究证明，Cc^+/0氧化还原电对在dialcarbs类离子液体中呈现可逆行为特征，可用作为内参比电对，并求得了其在各个离子液体中的扩散系数。然后研究了该类离子液体在Pt、GC、Au和Hg电极上的电化学窗口。求算出了离子液体体系的双电层电容值。并用旋转圆盘电极研究了该类离子液体体系中的稳态行为特征。该工作为离子液体的合成提供了一条新的思路。更多还原

【Abstract】 Today,with growing awareness in industry,academia and the general public ofthe need for sustainable development,the international chemistry community is underincreasing pressure to change current working practices and to find greener alternatives.Green chemistry,also known as sustainable chemistry,refers to environmentally friendly chemicals and processes that result in:reduced waste,eliminating costly end-of-the-pipe treatments;safer products;and reduced use ofenergy and resources—all improving the competitiveness of chemical manufacturersand their customers.One principle of Green Chemistry is to maximize atom economy,which is todesign syntheses so that the final product contains the maximum proportion of thestarting materials.Electron has been used as reagent in electroorganic synthesis,avoiding the use of other reducing agent and oxidant.This feature is often cited asbeing environmentally favorable.So compared with traditional organic synthesis,electrochemical synthesis is greener.Another principle of Green Chemistry is to use safer solvents and reactionconditions.Because of claimed advantageous chemical,physical and green propertiesrelated to negligible vapor pressure,low toxicity,high chemical stability,high thermalstability and the ability to dissolve a wide range of organic and inorganic compounds,ionic liquids have been suggested to provided a useful alternative to the use of volatileorganic solvents in organic synthesis,solar cell applications,solvent extractionprocesses.On the basis of high conductivity,significant electrochemical stability andwide potential windows,ionic liquids can be directly used as solvent and electrolytein electrochemistry,avoiding the use of other supporting electrolyte.Hence,ionicliquids have been recognized as green solvent.Carbon dioxide is the largest contributor to the green house effect,which mayincrease the earth average temperature to such a value that may cause catastrophicevents.Therefore great effort has been placed toward the reduction of CO₂ atatmospheric loading.On the other hand,CO₂ can be proposed as a Cl building blockin organic synthesis.Electrochemical carboxylation is one of the most useful methodsfor the fixation of CO₂ to organic molecules because it is a clean and environmentallybenign process.It takes place efficiently even in an atmospheric pressure of CO₂ under neutral and mild conditions to give carboxylic acids in high yield.2-Phenylsuccinic acids and cyano-phenyl-propionic acids are of interest due totheir biochemical properties and also are key molecules in synthesis of medicaments.In these preparations,however,there are several drawbacks:the use of hazardousreagents,expensive and complicated catalysts,high pressure and high temperature.Therefore,alternative methods of synthesis are highly desirable.Under mild condition,fixation of greenhouse gas-CO₂,to synthesis ofcarboxylic acids and corresponding esters by electrochemical synthesis,is veryimportant.Especially,use of ionic liquids as solvent for electrochemical fixation ofCO₂ is significant.The details are given as follows:（1） Electrosynthesis of 2-phenylsuccinic acidElectrochemical dicarboxylation of styrene in the presence of atmosphericpressure of CO₂ with a Ti cathode and a Mg rod anode readily took place efficiently ina MeCN solution containing 0.1 mol L^-1 Et₄NBr to give 2-phenylsuccinic acid.Influences of the nature of the electrodes,the current density,the passed charge andthe temperature on electrolyses were studied to optimize the electrolytic conditions,with the maximal isolated yield to be 86.1%.The mechanism of theelelctrocarboxylation process has been studied by cyclic voltammetry.（2） Electrochemical reduction and carboxylation of ethyl cinnamateThe electrochemical reduction and carboxylation of ethyl cinnamate has beencarried out in undivided cell equipped with Mg sacrificial anode and using MeCN assolvent.Directly electroreduction leads to the formation of the hydrodimers andsaturated ester.And electrocarboxylation was carried out in the presence of CO₂.Theglobal yield and the ratio of mono-and dicarboxylic acids are strongly affected byvarious factors:electrode material,electrolysis potential,the substrate concentrationand temperature.The highest yield（78%）was obtained at the optimized reactioncondition(cathode:Ni;electrolysis potential:-1.7 V;substrate concentration:0.1 molL^-1;temperature:-10℃).（3） Electrocarboxylation of cinnamate estersElectrochemical carboxylation of cinnamate esters has been carried out bycathodic reduction of C=C bond in an undivided cell equipped with Mg sacrificialanode and using MeCN saturated with CO₂ as solvent.The yield and the ratio ofmono-and dicarboxylatic acids are strongly affected by various factors:cathodic material,current,charge and temperature.The highest yield（78.9%）was obtainedstarting from ethyl cinnamate.Cyclic voltammograms have been measured andreaction pathways have been proposed.（4） Electrochemical reduction and carboxylation of cinnamonitrileCyano-phenyl-propionic acids were synthesized simply and efficiently byelectrocarboxylation of cinnamonitrile in undivided cell using non-noble metal nickelas cathode and magnesium as anode.The radical anion generated by theelectroreduction of cinnamonitrile in the absence of CO₂,is involved in severalcompetitive reactions which lead to the formation of linear hydrodimer,cyclichydrodimer,saturated dihydro product and glutaronitrile derivative.While under 1atm of CO₂,the electrocarboxylation could easily be carried out in the absence ofadditional catalysts,and with good yield（84.8%）.The influence of various synthesisparameters,such as the nature of the electrode,the working potential,theconcentration and the temperature,to the electrocarboxylation reaction wasinvestigated.（5） Electrocarboxylation of activated olefins in ionic liquidThe feasibility of electrocarboxylation of activated olefins has been investigatedin CO₂-saturated room-temperature ionic liquid BMEMBF₄ solution for the first time.The electrochemical behavior has been studied on GC electrode by cyclicvoltammetry,showing a diffusion controlled irreversible reduction process.Thesynthesis has been carried out under mild(P_CO2=1 atm,t=50℃)and safeconditions in undivided cell,and the use of volatile and toxic solvents and catalysts,as well as of any supporting electrolyte,was avoided.Monocarboxylic acids wereobtained in moderate yield（35%-55%）.Furthermore,the ionic liquid has beenrecycled for five times,which did not affect the product yield greatly.（6） Electroreduction of coumarin in ionic liquid BMIMBF₄The electroredution of coumarin was studied in ionic liquid（BMIMBF4）.Theinfluence of sweep rate,concentration and temperature by cyclic voltammetry,showsthat the reaction was irreversible and diffusion controlled.The diffusion coefficientD of coumarin in BMIMBF4 was 5.066×10^-7cm² s^-1.The product of constantpotential electrolysis is dimeric coumarin.And the same time the influence of waterand substituted group to the electroreduction was discussed.These preliminaryelectrochemical experiments appear as encouraging results for the use of ionic liquidsin a "green" electrochemistry. （7） Electrocatalysis of PhCH₂Cl and CO₂ by Co（L）in ionic liquidsThe electrochemical behavior of CoL（cobalt Schiff base complex）has beenstudied in ionic liquids.Its catalytic reactivity towards the reduction of PhCH₂Cl andthe reaction between PhCH₂Cl and CO₂ has also been investigated.CoL shows adiffusion controlled one-electron reversible peak couple in ionic liquids.Theelectrochemical behavior shows that the peak potential will not be influenced by theSchiff base ligand and the anion of the ionic liquids.CoL could catalyze the reductionof PhCH₂Cl by the voltammograms.The mechanism involves a one-electronreduction and a chemical reaction followed by another one-electron reduction.Andthis system could also catalyze the reaction between PhCH₂Cl and CO₂.Controlled-potential electrolysis led to （PhCH₂）₂CO,indicating that CO₂ can be fixedin ionic liquids by the catalysis of CoL.（8） Electrochemical properties of new ionic liquids dialcarbsThe viscosity,conductivity and electrochemical stability of several distillableroom temperature ionic liquids dialcarbs are reported.The temperature dependence ofviscosity and conductivity are analyzed for MEETCARB,and the influence of the ionsize on conductivity is discussed.The voltammetry of IUPAC recommended potentialscale reference system,cobalticenium/cobaltocene has been evaluated found to beideal in dialcarbs.Potential windows of dialcarbs have been compared on GC,Au,and Hg electrode,using Cc^+/0as reference.Diffusion coefficients and double layercapacitances have also been calculated.Steady-state behavior has been investigatedby using RDE.更多还原