Flash photolysis/HPLC method for studying the sequence of photochemical reactions: applications to 4-chlorophenol in aerated aqueous solution

Abstract

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 (bdI) in aerated aqueous solution (6.3 × 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.