Photochemical oxidation of C-14-labelled oxalic acid by cerium(IV) sulfatein acidic solution

The kinetic parameters for the reaction between C-14-labelled oxalic acid a nd Ce(IV) in a H2SO4 medium were determined in the presence and absence of ultraviolet radiation using a scintillation technique. The thermal reaction was also monitored by the stopped-flow spectrophotometric method. A new re action mechanism based on the behaviour of a photoactive sulfate hydrogen o xalato cerium(IV) ion as an intermediate species prior to the rate-determin ing oxidation step is suggested. The increase in activation energy with an increase in [H+] In the H2SO4 medium is explained in terms of the endotherm ic formation of this intermediate Ce(IV) complex ion.