The chemistry of cycloheptatriene: Part III: Formation of tropylium salts by autoxidation of cycloheptatriene in acidic media

Tropylium perchlorate and fluoroborate have been prepared by the autoxidation of cycloheptatriene dissolved in acetic acid containing perchloric or fluoroboric acid, respectively. An optimum yield of 60 % (calculated on the strong acid) is obtained by employing twice as much cycloheptatriene as strong acid, 1.4 mmole/1 of an iron salt as a catalyst and a temperature between 40 and 50°. In addition to acid catalysis the reaction shows free‐radical characteristics. These phenomena are discussed in relation to possible mechanisms. The formation of benzene and carbon monoxide from tropylium salts and hydrogen peroxide is markedly retarded by increasing the acidity of the medium (H0) from +1.20 to −1.20.