Halogens pyrolytic elimination reactions

The pyrolytic decomposition of the sodium salts of various fluorinated carboxylic acids to give isomeric unsaturated compounds has also been reported. The products were identified as alkenes with the C = C bond inside the carbon chain, mainly alk-2-enes. This isomerization may be catalyzed by the coal-like products formed during the pyrolytic decarboxylation of the salts, but the metal fluoride formed in the reaction may also be responsible for the isomerization. When potassium perfluoro(5-chloropentanoate) is heated in a rocking autoclave at 300 C for 2 hours, perfluorobut-2-ene (2b) is isolated in 82% yield.This is only possible by migration of the double bond away from the terminal position after carbon dioxide elimination and halogen exchange to form potassium chloride. ... 

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