By dehydrofluonnation

Dehydrofluorination by primary and secondary aliphatic amines occurs at room temperature and is the basis of diamine cross linkmg, which occurs by dehydrofluonnation and subsequent nucleophihc substitution of the double bond The locus of dehydrofluonnation is a VDF unit flanked by two perfluoroolefin units This selectively base-sensitive methylene group also undergoes elimination as the first step in phase-transfer-catalyzed cross-hnking with quaternary ammo mum or phosphomum salts, bisphenols, and morganic oxides and hydroxides as HF acceptors [31, 32]... 

MonofluoToalkanes and vicinal difluoroalkanes are dehydrofluonnated if strong enough bases are applied [10 12] In 5-fluorononane and fluorocyclodo-decane, elimination by means of sodium methoxide in methanol gives cis- and trans allcenes in respective yields of 8 and 21% and in ratios of 1 2 2 2 4, however, the bulky lithium diisopropyl amide m tetrahydrofuran produces trdns-isomers almost exclusively The strength of the base does not have much effect on the rate of elimination, but the lithium cation causes considerable acceleration [10] (equation 10)... 

Most aliphatic [95, 184, 185, 186, 187], aromatic [95 186,188], and heterocyclic [189,190] ketones react with DAST in the usual way to give geminal difluoro derivatives Fluorination of cycloaliphatic ketones, in particular, is often accompanied by a spontaneous dehydrofluonnation to form considerable amounts of... 

Dehydrofluonnation of compounds in which a single hydrogen is flanked by heavily fluorinated groups is achieved by aqueous or alcoholic alkali hydroxides and proceeds probably by theElcB mechanism Thus 1 -(2//-hexafluoropropyl)ada-mantane [25] and 1,3 bis(2// hexafluoropropy])adamantane [16] are dehydro-fluorinated in respective yields of 75 and 81% (equation 14)... 

Polyfluorocyclohexanes are dehydrofluonnated by potassium hydroxide to polyfluorocyclohexenes and polyfluorocyclohexadienes (where applicable) The reaction is sometimes very complex [17] (equation 15)... 

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