Heterogeneous fluorination of chlorine containing polymers with 18-crown-6 as phase transfer agent

Effectiveness of alkali metal fluorides, complexed with crown ethers, as fluorinating agents, was investigated in nitrobenzene as mediating solvent. Partial fluorination of the surface of the crosslinked film of chlorinated polyethylene occurs within the first 2 h at 80°C. Further reaction leads to dehydrochlorination only. Up to 50% of chlorine in polyepichlorhydrin (Herchlor-H) may be replaced by fluorine. Further reaction is strongly inhibited by the presence of fluorine substituents in the neighbourhood of unsubstituted chlorines. ‘Plateau’ is reached after about 10 h at 140°C. In all investigated systems elimination, E, competes with substitution, S. It was suggested that the same transition state complex may be responsible for the two reactions. The energy of activation of the two processes is ～5 kcal mol^?1. The $\text{S}\text{E}$ ratio decreases in the following order: primary > Secondary >>> vicinal.