Electrochemical Reduction of Halobenzenes in the Presence of Carbon Dioxide

Abstract

The　electrochemical　reduction　of　halobenzenes　in　the　presence　of　CO2 on　a　Hg　cathode　was　investigated. The　reduction　of　iodobenzene　and　bromobenzene　under　CO2 yielded　benzoic　acid　as a　fixation product　of　CO2．However，the　reduction　of　CO2 in　the　presence　of　chlorobenzene　produced　no　benzoic acid. It　is　confirmed　that　the　reduction　of　halobenzenes　is　important　to　fixate　CO2 on　phenyl　group and　the　reaction　of　CO2 with　halobenzenes　is　slow. In　the　present　electrolysis，the　phenylmercury radical is　considered　as　an　intermediate　for　the　formation　of　benzoic　acid． The electrochem. reduction of halobenzenes was studied in the presence of CO2 on a Hg cathode. The reduction of iodobenzene  [591-50-4] and bromobenzene  [108-86-1] under CO2 yielded benzoic acid  [65-85-0] as a fixation product of CO2. However, the reduction of CO2  [124-38-9] in the presence of chlorobenzene produced no benzoic acid. The reduction of halobenzenes was confirmed to be important in CO2 fixation on the Ph group, and the reaction of CO2 radical anion [14485-07-5] with halobenzenes was slow. The phenylmercury radical is considered to be an intermediate for the formation of benzoic acid.