Specific Anion Effects on the Kinetics of Iodination of Acetone.

Specific ion effects on the kinetics of iodination of acetone in an acidic medium are investigated by UV/Vis spectrophotometry as a function of nature of the acid and temperature. The results indicate that the order of the reaction with respect to acetone is practically unaffected by the composition of the acid while the value of the mixed constant k1 K increases according to the sequence HBr<HCl<HClO4 <HF<H2 SO4 <H3 PO4 . The results are discussed in terms of the hydration free energy and size of the anion and of the interaction between the cationic intermediate and the anion.