DEGRADATION OF PHENOL AND SALICYLIC-ACID BY ULTRAVIOLET-RADIATION HYDROGEN-PEROXIDE OXYGEN

Based on the oxidation reactions of u.v. radiation/hydrogen peroxide/o xygen with either phenol or salicylic acid a spectra library was estab lished. The reaction products contain hydroxylated phenols, benzoquino ne and aliphatic acids with up to six carbon atoms. Many of the substa nces have been identified by means of chromatography and spectra compa rison. From the observed concentrations of the substances and the know n reaction mechanisms the following course of reaction has been postul ated. The first reaction step is the hydroxylation of the aromatic rin g. Further oxidation occurs via abstraction of a hydrogen atom to form 1,2-benzoquinone which is cleaved to form muconic acid. The cleavage of the muconic acid by u.v. radiation/hydrogen peroxide/oxygen leads t o maleic acid, fumaric acid and oxalic acid. The degradation of oxalic acid leads to formic acid and finally to carbon dioxide. The hydroxyl ation of the double bond of the maleic or fumaric acid and the abstrac tion of a hydrogen atom produces malic acid. The reactions can be seen as essential step in the photochemical transformation of refractory s ubstances into biodegradable ones.