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

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 AlF3, MgF2, CaF2, SrF2, and BaF2 as catalysts that are prepared according the fluorolytic sol–gel synthesis. AlF3 is exclusively selective toward dehydrofluorination, whereas BaF2 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.

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.Figure optionsDownload high-quality image (46 K)Download as PowerPoint slideHighlights
► 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.