K. Momota, K. Mukai, K. Kato
1998
Citations
0
Influential Citations
15
Citations
Journal
Electrochimica Acta
Abstract
Electrochemical fluorinations of toluene (1a), monofluoromethylbenzene (1b) and difluoromethylbenzene (1c) in neat Et 4 NF.mHF (Et = C 2 H 5 , m = 3.5 or 4.0) were carried out on a platinum anode at 1.9-2.7 V vs Ag/Ag + (0.01 mol dm -3 ). The anodic fluorination of 1a produced exclusively 1b as the primary product. The fluorination of 1b occurred competitively both on the side-chain (formation of 1c) and on the benzene-ring (formation of l-monofluoromethyl-2-fluorobenzene (2b) and 1-monofluoromethyl-4-fluorobenzene (4b)). However, the fluorination of 1c occurred only on the benzene-ring, and three kinds of difluoromethylfluorobenzenes (1 -difluoromethyl-2-fluorobenzene (2c), 1-difluoromethyl-3-fluorobenzene (3c) and 1-difluoromethyl-4-fluorobenzene (4c)), were obtained as the primary products. These results are explained by the facility of proton elimination from the methyl groups of the radical cations which have been formed by the anodic one-electron transfer reactions of 1a, 1b and 1c. A cyclic voltammogram of 1a (0.01 M) showed the characteristic three anodic current peaks which correspond to the oxidation of 1a (E p 1 = 1.80 V), 1b (E p 2 = 2.04) and 1c (E p 3 = 2.24). Therefore, the profile of the fluorination products during the fluorination of 1a varied with the applied potentials.