Addition of halogen to polyenes

4- dichloro-2-butene. The corresponding c/s-compound49 is obtained from c/s-2-butene- 

Further information about the addition of halogen to butadiene is given in some earlier papers.34,47 

Polyenecarboxylic acids add bromine most easily at the C=C bond furthest removed from the COOH group.54 

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