FLASH-PHOTOLYSIS HPLC METHOD FOR STUDYING THE SEQUENCE OF PHOTOCHEMICAL-REACTIONS - APPLICATIONS TO 4-CHLOROPHENOL IN AERATED AQUEOUS-SOLUTION

A new method involving the use of flash photolysis followed by rapid high performance liquid chromatography analysis is described and applied to the examination of the photodegradation of 4-chlorophenol (I) in aerated aqueous solution (6.3 x 10(-4) M). Analysis after a single flash indicates that p-benzoquinone (II) is the only observed photoproduct. Irradiation with a more intense flash or with multiple flashes yields other products (principally hydroxy-p-benzoquinone (III) and hydroquinone (IV)), which are known photoproducts of the photolysis of II. The photoreaction of I is relatively independent of pH, except that above pH 7 the product distribution changes in accord with the known dark chemistry of II at high pH. Oxygen is a reagent in the photoreaction of I, as bubbling with argon significantly decreases the yield of II. This new method should be particularly useful for studying photochemical reactions in dilute solutions, since photolysis of intermediate products can be avoided.