PREPARATION OF GEOMETRIC ISOMERS OF SOME POLYFLUORO-2-BUTENES

The preparation of 2H-heptafluoro-2-butene from hexachloro-1,3-butadiene and potassium fluoride, using N-methyl-2-pyrrolidone as solvent, has now been found to give the trans isomer (95%), Dehydrohalogenation of pure diastereomeric forms of 2H-2,3-dichloroheptafluorobutane and 2H-2,3-dibromoheptafluorobutane, formed by the free radical addition of,the halogen to 2H-heptafluoro-2-butene gives pure cis and trans isomers of 2-chloroheptafluoro-2-butene and 2-bromoheptafluoro-2-butene, cis and trans-Octafluoro-2-butene are prepared by dehydrobromination of individual diastereomers of 2H-3-bromo-octafluorobutane. © 1969.