Highly selective metal fluoride catalysts for the dehydrohalogenation of 3-chloro-1,1,1,3-tetrafluorobutane

Using nanoscopic metal fluorides as catalysts, 3-chloro-1,1,1,3-tetrafluorobutane can be selectively converted into the respective olefins by either AlF3 (dehydrofluorination, X > 99%, S = 100%) or BaF2 (dehydrochlorination, X = 98%, S = 100%). A mechanistic rationalization is presented. [Display omitted] ► New nanoscopic metal fluoride catalysts with tunable Lewis acid/base sites. ► A 100% selectivity toward either dehydrofluorination or dehydrochlorination. ► Mechanistic explanation based on fluorine and chlorine affinities. ► Major impact on dehydrochlorination reactions in the chlorohydrocarbon chemistry. For the first time, dehydrochlorination and dehydrofluorination reactions are studied on the same substrate, 3-chloro-1,1,1,3-tetrafluorobutane, employing nanoscopic metal fluorides AlF 3, MgF 2, CaF 2, SrF 2, and BaF 2 as catalysts that are prepared according the fluorolytic sol–gel synthesis. AlF 3 is exclusively selective toward dehydrofluorination, whereas BaF 2 is 100% selective toward dehydrochlorination. The acid–base character of the catalysts is investigated and, as a result, mechanistic proposals for the dehydrofluorination and the dehydrochlorination are given. Thus, at high conversion level, selective catalysts for both dehydrofluorination and dehydrochlorination on the same substrate have been developed.