FLASH-PHOTOLYSIS HPLC APPLICATIONS .2. DIRECT PHOTOLYSIS VS HYDROGEN-PEROXIDE MEDIATED PHOTODEGRADATION OF 4-CHLOROPHENOL AS STUDIED BY A FLASH-PHOTOLYSIS HPLC TECHNIQUE

A method involving UV flash photolysis followed shortly by HPLC analysis of products has been applied to the study of the partial photooxidation of 4-chlorophenol (I). In this study we have compared the distribution of photoproducts obtained under conditions of hydrogen peroxide mediation with our earlier reported work on the direct photolysis of I. There it was found that the photolysis of I, stimulated by single flashes, yields quantitative amounts of p-benzoquinone (II) as the only primary photoproduct. When the concentration of H2O2 is increased to greater than 20 times that of I, the photolysis products change over to a different set. Now the major product is 4-chlorocatechol (VI) with smaller amounts of hydroquinone (IV) and 1,2,4-trihydroxybenzene (V). When several flashes are applied, IV and V become the most significant products; however, the overall yield of products IV-VI decreases, indicating that further oxidative degradation of the reaction mixture is occurring.