C-14! UL-CHLOROTHALONIL - A STUDY OF THE CATALYTIC CHLORINATION OF C-14! UL-1,3-DICYANOBENZENE

C-14!-UL-2,4,5,6-tetrachloro-1,3-dicyanobenzene (chlorothalonil, 2) w as prepared by catalytic chlorination of C-14!-UL-dicyanobenzene (1) on activated carbon, in a tubular reactor at a controlled temperature and in a stream of chlorine. Optimization of the ratio between the cat alyst (activated carbon, 30-60 mesh) and the inert support (glass bead s, silicagel 0.2-0.5 mm) as well as the geometry of the column reactor , the temperature of the preheated chlorine and the reaction temperatu re was studied in ca 90 ''cold'' experiments. At 300-degrees-C gas tem perature, 300-degrees-C reactor temperature, 5 mL/min flow rate of chl orine, and a catalyst:silicagel support:1 ratio (1:7:0.25), the reacto r design produces C-14!-UL 2 in over 90% chemical yield and ca 95% pu rity (GLC). On purification by column chromatography on silicagel, wit h toluene-n-hexane (2:3, v/v) as eluant, 99.6% pure C-14-UL 2 (sp. act . 9.2 MBq/mmol, 0.242 mCi/mmol) is obtained.