Catalytic fluorination of trichloroethene by anhydrous hydrogen fluoride in the presence of fluorinated chromia under static conditions. Synthesis of[F-18]-labelled CF3CH2F and [Cl-36]-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 condit ions leads to a mixture of products in which partially halogenated olefins predominate. These are converted to mixtures containing CF3CH2F and CF3CH2C l by a second fluorination using fresh catalyst. The results of product ana lyses 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 b y 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 th e vapour phase have been computed.(1) (C) 2000 Elsevier Science S.A. All ri ghts reserved.