title: Chemical and thermodynamic characteristics of the isotopic exchange reaction between radioiodine and iodohippuric acid isomers.
abstract: The parameters affecting the absolute radiochemical yield of the isotopic exchange reaction between radioiodine (125I-) and iodohippuric acid isomers on molten ammonium acetate as a medium exchange at 120 degrees C without any carrier added (radioiodine, 125I-) was determined. The isotopic exchange reactions of radioiodine as 125I- for iodine-127 of o- and p-iodohippuric acid isomers occur more rapidly than m-iodohippuric acid isomer. These reactions proceed by nucleophilic second order substitution reaction. The kinetics and thermodynamic parameters of these isotopic exchange reactions were determined. The absolute radiochemical yield and radio pharmaceutical purity were determined by HPLC and TLC techniques.