Organic Electrosynthesis - Fundamentals and Applications of Organic Electrochemistry - page 245

(6.23)
In neat ionic liquid fluoride salts, the
nucleophilicity of fluoride ions is rather low,
resulting in poor fluorination yields. It has been
demonstrated that ether solvents like DME
enhance the nucleophilicity of fluoride ions, but
DME is rather easily decomposed [63]. In
contrast, PEG and even its oligomer are stable
against anodic oxidation, and it was found that
the addition of only about 3% PEG oligomer to
the reaction system greatly improved the yield
due to its ability to coordinate the counter
cations of fluoride ions, as shown Eq. 6.24 [64].
(6.24)
Severe passivation of the anode often occurs
even in ionic liquid HF salts. Use of mediators