Radiotracers in fluorine chemistry. Part IX fluorination of chlorofluoroethanes by chromia catalysts treated with hydrogen fluoride or hydrogen [18F]-fluoride

Passage of dichlorotetrafluoroethane isomers or 1,1,2-trichloro- 1,2,2-trifluoroethane at temperatures ? 623 K over chromia catalysts, previously treated with hydrogen fluoride at 623 K, leads to the formation of fluorinated and chlorinated products. Incorporation of fluorine-18 radioactivity in the products is observed when hydrogen [¹⁸F]-fluoride is used in the catalyst pretreatment, indicating the involvement of a surface fluorine- containing species. The reactions observed are described in terms of series of F-for-Cl and Cl-for-F halogen exchange reactions occurring at the catalyst surface.