The oxidation of ethanol by hydrogen peroxide. Part I. Catalysis by ferric ion
In acid conditions and the presence of 7% of water, the principal products of the ferric ion-catalysed oxidation of ethanol by hydrogen peroxide are acetaldehyde and diethylacetal. The rate-determining step is shown to be independent of acidity and involves the species Fe(H2O2)3+, solv. and not Fe(HO2)2+,solv, which is thought to be active in the ferric ion-catalysed decomposition of hydrogen peroxide in aqueous solutions.
When hydrogen peroxide is added to a boiling ethanolic solution of ferric perchlorate within one minute of the introduction of the ferric salt, the reaction is catalysed by the ferric ions remaining after the rapid establishment of the equilibrium (i), the species Fe2(H2O2)26+,solv. being inactive in the oxidation reaction. 2Fe3+,solv. + 2H2O2⇌ Fe2(H2O2)26+,solv. (i)
It is found that the initial rate of reaction is given by (ii), where CM is the total ferric perchlorate concentration, [graphic omitted] =k0[Fe3+][H2O2]=k0[graphic omitted] (ii)[Fe3+] is the concentration of ferric ions remaining after the establishment of the above equilibrium for which the equilibrium constant is K, [H2O2] is the initial hydrogen peroxide concentration, and k0 the overall rate constant of the oxidation (iii) C2H5·OH + H2O2→ CH3·CHO + 2H2O (iii)k0 is independent of the acidity of the reaction medium.
The values of k0 and K at 70·1° were found to be 9950 ± 850 mole–1l.min.–1 and 7·2 ± 0·7 × 104 mole–3l.3, respectively.