Autoxidation of Hydrocarbons in the Presence of Boric Acids Decomposition of Aromatic Hydroperoxides

The autoxidations of aromatic hydrocarbons are inhibited by the addition of boric acids and their derivatives, whereas the oxidations of aliphatic and alicyclic hydrocarbons are not inhibited and give selectively a boric ester of the corresponding secondary alcohol. In order to clarify these facts, tetralyl and cumyl hydroperoxides were decomposed by several types of boric acids and their derivatives. The rates of decompositions of these hydroperoxides were significantly accelerated by the boric acids and their derivatives, and γ-o-hydroxyphenylbutylaldehyde and phenol were produced selectively from tetralyl and cumyl hydroperoxide respectively. It was found that the faster the inhibition of the oxidation of tetralin, the higher the activity of the boric acids and their derivatives in the decomposition of tetralyl hydroperoxide. The acid strength of the boric acids was found to be much larger than that known as Bronsted acids. It was concluded that the boric acids acted as Lewis acids and not as Bronsted acids in the decomposition of aromatic hydroperoxides.