fluorine acceptor which defluorinates perfluoroalkanes with the partial structure (Rf)2CFCF(Rf)2 to alkenes and perfluoroalkenes to dienes. Carbon catalyzes double-bond shifts, as well as cis/trans and ring-chain perfluoro-olefin isomerizations. Carbon effectively catalyzes TFE and HFP dimerizations. Less effectively, carbon catalyzes further oligomerization of TFE to give low yields of linear, internal olefins