Decomposition of hydroperoxides by boric acid anhydride in solution. Electrophilic hydroxylation of the solvent

Abstract

Three kinds of hydroperoxides were decomposed in aliphatic and aromatic hydrocarbons in the presence of boric acid anhydride at 100 °C in order to study the hydroxylation of the solvent. Secondary 1-methylheptyl hydroperoxide was decomposed by boric acid anhydride to give mainly octan-2-ol and its borate ester, and when n-pentane, n-hexane, benzene, and mesitylene were used as solvent they were simultaneously hydroxylated to secondary pentanols, secondary hexanols, phenol, and mesitol respectively. In the decomposition of t-butyl hydroperoxide, the solvent was hydroxylated to the corresponding alcohol or phenol, but t-butyl alcohol formed was dehydrated to isobutene. Acid-catalysed rearrangement of t-butyl hydroperoxide to acetone and methanol also took place. Cumyl hydroperoxide was decomposed exclusively to phenol and acetone and little cumyl alcohol and hydroxylation of solvent were observed. It was suggested that the solvent was hydroxylated not by free atomic oxygen or by a radical process but by an ionic, electrophilic substitution reaction where boron acted as electron acceptor and hydroperoxide oxygen as electron donor, generating an active hydroxonium ion.