ELECTROCHEMICAL ACTIVATION AND DEHALOGENATION OF FREONS IN LOW-TEMPERATURE IONIC LIQUIDS

The effect of various factors (the nature of the medium and the electrode material, the electronic structure of the Freons, etc.) on the electrochemical activation and dehalogenation of a series of Freons [F113 (CF2ClCFCl2), F13B1 (CF3Br), F114B2 (CF2BrCF2Br), and F113B2 (CFClBrCF2Br)] in various low-temperature ionic liquids (LTIL) [1-butyl-3-methylimidazolium, 1-butyl-1-methylpyrrolidinium, and trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imides and 1-butyl-3-methylimidazolium hexafluorophosphate, tetrafluoroborate, and trifluoroacetate] at various electrodes (glassy carbon, Pt, Ag) was studied. It was established in particular that the investigated processes are affected substantially by the electrical conductivity and viscosity of the medium. With decrease of the latter the peak potential in the cyclic voltammetry of the electrochemical reduction of the Freons is shifted toward less negative values while the current increases. It was found that a silver cathode has a specific effect on the electrochemical activation of the Freons in the LTILs, and this may be due to the formation of complexes Ag…Hal…Rf between the Freons and silver atoms on the electrode surface, in which cleavage of the C—Hal bond is facilitated. Such processes are compared with the processes realized in the traditional solvent dimethylformamide.