Identification of the Products of Alkylphenol Oxidation by Iron(III) Chloride Using HPLC–Mass Spectrometry

Abstract

We analyzed the products of alkylphenol (ortho-, meta-, and para-cresols and 4-isopropylphenol) oxidation by iron(III) chloride in aqueous solutions by HPLC with electrospray ionization and mass-spectrometric detection in the negative ion mode. It was found that the main products formed by the nucleophilic addition of the initial alkylphenols to reactive intermediates, quinone methides. The resulting adducts can be further oxidized, which, after several oxidation–addition cycles, leads to the appearance of a series of compounds with molecular weights belonging to sequences of values of 108, 214, 320, 426, 536, 638, … for cresols and 136, 270, 404, 538, 672, … for 4-isopropylphenol. Such processes are similar to the oxidation of alkylphenols by air oxygen in aqueous solutions and to their electrochemical oxidation yielding dimeric and oligomeric products.