The Fenton reaction in aerated aqueous solutions revisited

The oxidation of alcohols in aerated acidic aqueous solutions by the Fenton reagent is a chain reaction. The length of the chain depends linearly on the number of CH_nOR (n = 1 or 2) groups in the alcohol. The reaction is accelerated by increasing the concentration of Fe(H₂O) ₆²⁺, but this cation is also active in at least one of the termination steps of the chain reaction. Addition of ethanol to a solution containing sucrose shortens the chain length. Saturation with dioxygen, instead of air, increases the chain length. An increase in alcohol concentration increases the chain length up to a limiting value. A complicated mechanism, which is in agreement with all these observations, is proposed. However, efforts to simulate the mechanism succeed only in simulating the Fe(H ₂O)₆³⁺ yield, but indicate that the observed process is considerably faster than the predicted one. In the latter the rate-determining step is the Fenton reaction, the rate constant of which is well known.