A study of hydrogen exchange in nonbenzoid (surocene) aromatic systems

Abstract

1. Ferrocene enters into a hydrogen exchange reaction with various acids, deuterosulfuric, hydrochloric enriched with deuterium, deuterophosphoric acid, trichloracetic and glacial acetic acid solution, and trifluoracetic. 2. In the reaction between deuterosulfuric acid and ferrocene, the hydrogen exchange occurs at a higher rate than the oxidation of ferrocene to ferricinium cation. The ferricinium cation does not enter into hydrogen exchange with acids. 3. From studies made on the hydrogen exchange kinetics of ferrocene, acetyl ferrocene, diacetyl ferrocene, and toluene in benzene solution with trichloracetic acid, the exchange rate of ferrocene is greater by a factor of 1000 than the exchange rate of acetyl ferrocene and greater by a factor of 2000 than that of diacetyl ferrocene. Under these conditions, benzene does not enter into the hydrogen exchange reaction, while toluene exchanges at a rate three order of magnitude slower than ferrocene. 4. From the kinetic data on hydrogen exchange, the compounds investigated may be arranged in the following series in order of decreasing electrophilic substitution power: ferrocene-acetyl ferrocene-diacetyl ferrocenetoluene.