Halogens pyrolytic 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. ... 

The pyrolysis of 1-halo-l-methylsilacyclobutanes yielded primarily the head-to-tail dimers of the expected 1-halosilenes as well as significant amounts of their hydrogen halide adducts. In several of these reactions polymers were obtained as well159,186. The pyrolytic behavior of halogenated silacyclobutanes appears to be quite complicated, and although it is certainly possible that the initial products are ethylene and 1,1-dihalosilene almost exclusively, this has not been established beyond reasonable doubt. 

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