Catalytic fluorination of trichloroethene by anhydrous hydrogen fluoride in the presence of fluorinated chromia under static conditions.: Synthesis of [18F]-labelled CF3CH2F and [36Cl]-labelled CF3CH2Cl.: Catalytic dehydrofluorination of CF3CH2F and CF3CH2Cl

Catalytic fluorination of trichloroethene by anhydrous hydrogen fluoride at 653 K in the presence of fluorinated amorphous chromia under static conditions leads to a mixture of products in which partially halogenated olefins predominate. These are converted to mixtures containing CF3CH2F and CF3CH2Cl by a second fluorination using fresh catalyst. The results of product analyses from reactions carried out under various conditions have been used to design a synthesis of [F-18]-CF3CH2F from CCl2=CHCl. It is proposed that [F-18] labelling occurs via direct [F-18]- for [F-19] exchange rather than by a dehydrofluorination/hydrofluorination route. [Cl-36]-labelled CF3CH2Cl is readily prepared from CF3CH2F and (HCl)-Cl-36 in the presence of chromia catalysts. Enthalpies of dehydrofluorination of CF3CH2F and CF3CH2Cl in the vapour phase have been computed.(1) (C) 2000 Elsevier Science S.A. All rights reserved.