FAST HIGH-YIELD LABELING OF 16-BR-HEXADECANOIC ACID WITH RADIOACTIVE IODINE USING QUATERNARY AMMONIUM-SALTS

The catalytic effect of quatemary ammonium ion on the reaction between 16-bromohexadecanoic acid (16-BrHDA) with (NaI)-I-131 in two phase sy stem has been determined. The technique described here is based on non isotopic exchange reaction between 16-BrHDA and (NaI)-I-131 using phas e transfer catalysts. Four quatemary ammonium salts (as phase transfer catalyst PTC) and one crown ether were examined. The kinetics are lin early dependent on catalyst content, offering radiochemical yield of m ore than 90% within 10 minutes at 60 degrees C. The effect of differen t temperatures on the radiochemical yield of 16-(131)IHDA have been st udied to determine the activation energies of the exchange processes b etween 16-BrHDA and (NaI)-I-131. In the presence of PTC, the activatio n energies of 8.3-9.7 kcal/mol were determined. Also in dry state and in absence of PTC the activation energy was measured and found to be 2 1.95 kcal/mol.