NEW MATERIAL:A diene based fluorine-containing compound expressed by formula I (G represents 1W2C hydrocarbon group; X is 0 or 1; Z is alkoxy).

EXAMPLE: Methyl 5-chloro-2,3,4,5-hexafluoro-2,4-pentadienoate.

USE: A useful material suitable for use as functional high polymers such as ion- exchange membranes, surfactants, textile treating agents, emulsifiers, metal cleaners, solvents, surface treating agents, etc., and usable for other various applications.

PREPARATION: A compound expressed by formula II (Y represents 1W3 hydrocarbon group), obtained by telomerization of 1,2-dichloro-1,2-difluoroethylene with an 1W3C saturated alcohol, is oxidized with an oxidizing agent such as potassium permanganate. After oxidation, the resultant product is subjected to either dehydrochlorination followed by esterification or esterification followed by dehydrochlorination, and further subjected to dechlorination reaction to obtain the compound expressed by formula I.