EVALUATION OF THE REACTION PARAMETERS AND THERMODYNAMICS OF THE IODIDE-EXCHANGE PREPARATION OF RADIOIODINATED 15-(P-IODOPHENYL) PENTADECANOIC ACID BY BOTH SOLID-PHASE AND SOLUTION METHODS

Two isotopic exchange procedures are described for the labelling of 15 -(p-iodophenyl) pentadecanoic acid with radioiodine in the presence of ammonium sulphate and cuprous chloride as catalysts. The methods affo rded regioselective and high specific activity products with radiochem ical yields of 92% and 85% within relatively short reaction times. Hig h pressure liquid chromatographic separation resulted in high radioche mically pure product suitable for medical application. Kinetic studies revealed second order iodine-iodine exchange reactions with an activa tion energy of 13.7 Kcal/mole for the solid state radioiodination with ammonium sulphate and 15.3 Kcal/mole for the copper catalyzed exchang e reaction.