Electrochemical fluorination of organic

Meinert and others [85] have stated that their concept for the electrochemical fluorination of organic compounds is based on the assumption that the first step is the anodic oxidation of the organic molecule. The electrochemical process is promoted by weakening of the C-H bonds due to hydrogen-fluorine bridges. After anodic withdrawal, the C-F bond is formed by insertion of a fluoride ion, present in the Helmholtz-double-layer at the electrode surface. 

This chapter deals with recent advances in the application of electrochemical electron transfer reactions to the synthesis of fluorinated organic substances. The effect of fluorine atoms on the reduction and oxidation potentials of organic compounds is discussed first. Subsequently, recent applications of the electrochemistry to the conversion and functionalization of fluoro-organics (building-block approach) are described. Finally, methods for selective electrochemical fluorination of organic molecules (direct fluorination approach) are briefly considered. 

IV. Electrochemical Fluorination of Organic Compounds in Anhydrous Hydrogen... 

Fuchigami, T. and Inagi, S. (2011) Selective electrochemical fluorination of organic molecules and macromolecules in ionic liquids. Chem. Commun., 417, 10211-10223. 

As mentioned earlier, perfluorooctanesulfonyl fluoride and its homologues are prepared by electrochemical fluorination of organic compounds. " During the process, which was invented by Simons, the corresponding hydrocarbon sulfonyl fluoride or chloride is fluorinated in anhydrous HF by applying a direct electrical current with a voltage typically between 5 and 7 The elec-... 

Fuchigami T (2007) Unique solvent effects on selective electrochemical fluorination of organic compounds. J Fluorine Chem 128 311-316... 

HF is a reactive solvent in the electrochemical fluorination of organic compounds. In this approach, HF is oxidized in the presence of a hydrocarbon and the fluorine replaces C-H bonds with C-F bonds. Perfluorinated carboxylic acids and sulfonic acids are produced in this way. 

Direct fluorination of organic compounds using fluorine is an important methodology when considering safety, environmental and recycling problems. Fluorine can be fed into the reactor from a cylinder for the direct fluorination procedure, but this method has economic and safety disadvantages. Electrochemical generation of fluorine has recently been adopted for fluorination even in the laboratory. It can be operated easily and safely, because operational difficulties have been improved. 

Konno A, Naito W, Fuchigami T (1992) Electrolytic partial fluorination of organic compounds. 6. Highly regioselective electrochemical monofluorination of aliphatic nitrogen-containing heterocycles. Tetrahedron Lett 33 7017-7020... 

Electrochemical fluorination of various aromatic compounds such as benzene, substituted benzenes toluene, and quinolines is achieved at high current densities using these molten fluoride salts in the absence of organic solvent with good to high current efficiencies (66-90 %)... 

Other limitations of electrochemical fluorination ate that compounds such as ethers and esters ate decomposed by hydrogen fluoride and cannot be effectively processed. Branching and cross-linking often take place as a side reaction in the electrochemical fluorination process. The reaction is also somewhat slow because the organic reactant materials have to diffuse within 0.3 nm of the surface of the electrode and remain there long enough to have all hydrogen replaced with fluorine. The activated fluoride is only active within 0.3 nm of the surface of the electrode. 

Electrochemical Fluorination. In the Simons electrochemical fluorination (ECF) process the organic reactant is dissolved in anhydrous hydrogen fluoride and fluorinated at the anode, usually nickel, of an electrochemical ceU. This process has been reviewed (6). Essentially all hydrogen atoms are substituted by fluorine atoms carbon—carbon multiple bonds are saturated. The product phase is heavier than the HF phase and insoluble in it and is recovered by phase separation. 

Electrochemical fluorination in anhydrous hydrogen fluoride (Simons process) involves electrolysis of organic compounds (ahphatic hydrocarbons, haloalkanes, acid halides, esters, ethers, amines) at nickel electrodes. It leads mostly to perfluori-nated compounds, but is accompanied to a high extent by cleavage and rearrangement reactions. The mechanism of the formation of carbocations according to Eq. (1) and Scheme 1 is assumed... 

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