180
V. Suryanarayanan, M. Noel / Journal of Fluorine Chemistry 92 (1998) 177±180
and ef®ciency. The yield of mono¯uoro compound does not
exceed 30% in any of the solvent-supporting systems inves-
tigated.
COOPh), solvent supporting electrolyte system exert little
in¯uence on the overall yield and ef®ciency.
Hence, the solvent-supporting electrolyte system appears
to be important only in those cases wherever the yield in
CH3CN/Et3NÁ3HF is low and polymerisation and adsorp-
tion effects are also low. In these cases, solvent supporting
electrolyte systems have a profound in¯uence on the overall
yield and ef®ciency. PhCH2CN and PhSCH2CONH2 are the
typical cases in this category. In the case of PhCH2CN, all
the solvent-supporting electrolyte systems give higher
yields of mono¯uoro derivative, when compared to
CH3CN/Et3NÁ3HF. In the case of PhSCH2CONH2, sulfo-
lane, THF and DME are found to be the better solvents for
ef®cient selective electrochemical ¯uorination.
The present experimental results, however, are not sig-
ni®cantly broad to understand the exact cause for the widely
different effects of solvent-supporting electrolyte systems
on the overall yield and ef®ciency. Many solvent properties
can in¯uence the overall ef®ciency. Some possible causes
are solubility of reactants, stability of cation radicals gen-
erated in the solvent, the nucleophilicity of the solvent,
molecule and the solubility of ¯uorinated product in the
solvent-supporting electrolyte system.
Acknowledgements
VS thanks CSIR, New Delhi, for the award of Research
Fellowships. The authors also thank Volkswagen Stiftung,
Germany, for the ®nancial support of this work. Thanks are
also due to Mr. S. Govindu for the analytical assistance.
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