Selective Electrocarboxylation Of Bromostyrenes

Electrocarboxylation is an important way of carbon dioxide fixation. Electrocarboxylation of organic halides can not only fix and take advantage of CO2, and slow down the greenhouse effect, but also can transform poisonous and harmful halides to useful organic products. Electrochemical ways to fix CO2 is greatly meaningful by using electrons as reactant, according with the idea of green chemistry. So far, most studies about electrocarboxylation focused on the substrates with only one reducible functional group, while a few papers concerned with substrates bearing two reducible groups. If the substrate bears two or more reducible groups, the reaction pathway must be very complex, by then the selectivity of the reaction would deserve attention.This study will choose compounds which contain two electroactive groups, C=C bond and C-Br bond, as the research object, bromostyrenes, for example. We try to control the reaction condition in which only C-Br bond will be reduced and C=C bond remains the same, so that vinyl-benzoic acid methyl ester will be obtained as the principal product. Firstly cyclic voltammograms and potentiostatic electrolysis have been used to study the electrorcarboxylation of 4-bromostyrene. Under ambient temperature and normal pressure, potentiostatic electrolysis was carried out in DMF solution containing 0.1 mol L-1 14-bromostyrene in an undivided cell. And the applied potential was exactly controlled around the reduction potential of C-Br bond. As expected,4-vinyl-benzoic acid methyl ester was obtained as the principal product, accompanied by styrene. The influence of various synthetic parameters, such as supporting electrolyte, electrode material, applied potential, electric charge, and temperature, have also been investigated in detail. To investigate the influence of the C=C position on phenyl ring, similar research for 2-bromostyrene and 3-bromostyrene was carried out. Cyclic voltammograms and potentiostatic electrolysis results both show that in the electrocarboxylation reactions,2-bromostyrene was the easiest, and then 3-bromostyrene,4-bromostyrene was the most difficult one.In recent years, with the development of theoretical chemistry, the nature of many reactions can be explored by theoretical calculation, which was gradually accepted. Theoretical chemistry was usually supplemented by computer simulation. And Gaussian 09 software is exactly one kind of computer simulation. With the help of DFT theory in Gaussian 09 software, some calculation was carried out. We calculated the electroreduction of three bromostyrenes from the following two aspects. On the one hand, we calculated the electrocarboxylation passway of bromostyrenes with the effect of group positions. On the other hand, we calculated the influence of Ag atoms on reduction potential of C-Br bond.With the aid of DFT theoretical calculation, We found that different Ag atoms have great influence on the reduction of C-Br bond. Based on the above result, we then focused our attention on the new material loaded different Ag metal content. Nanoparticle has special properties in electrochemical reaction because of its small particle size. Here we loaded Ag metal on TiO2 to prepare Ag-TiO2 with different Ag metal content. By the way, the morphology characterization and catalytic performance research in this new material were carried out. We found that different Ag metal content did have great impact on the reduction of C-Br bond, and Ag-TiO2 material showed better effect of C-Br bond reduction than bulk Ag. Here we can conclude that Ag-TiO2 material is fairly promising to realize the selectivity reduction of bromostyrenes C-Br bond in electrocarboxylation.