OF SALTS OF PERFLUOROCARBOXYLIC ACIDS

Thermal decarboxylation of potassium salts of perfluorocarboxylic acids in the presence of 20 mole % of crown ethers takes place in i h at 180~ and gives internal perfluoroolefins in yields of up to 95%. The predominance in product mixtures of isomers whose double bond is adjacent to the trifluoromethyl group is associated with kinetic control of the reaction. The kinetic parameters of the process have been found and the relative activities of a series of crown ethers have been established. A scheme is advanced to show their influence on the reaction studied. We have previously investigated the role of crown ethers (Cw) in replacement of CI by F atoms [i]. In the present work it is shown for the first time that thermal decarboxylation (TD) of potassium salts of perfluorocarboxylic acids in the presence of Cw proceeds at reduced temperature to exclusive formation of internal perfluoroolefins