Polarographic Studies in Acetonitrile and Dimethylformamide VII . The Formation of Benzyne

Polarographic studies of the three isomeric dibromobenzenes and bromochlorobenzenes have been carried out in acetonitrile and dimethylformamide. The results with o‐dibromobenzene in these solvents point to an intermediate which eliminates a bromide ion and forms benzyne. The intermediate from o‐bromochlorobenzene under the same conditions undergoes partial elimination to benzyne. The elimination reaction also occurs to a slight extent for o‐dibromobenzene in aqueous dioxane. The formation of benzyne was verified by a large‐scale electrolytic reduction of o‐dibromobenzene in dimethylformamide in the presence of furan. The tarry product obtained on acid hydrolysis gave a 1 % yield of α‐naphthol.