Anodic bromination of anisole in acetonitrile

• Published in: Journal of electroanalytical chemistry and interfacial electrochemistry 1982-01, Vol.132, p.233-245
• Main Authors: Taniguchi, Isao, Yano, Masako, Yamaguchi, Hiroko, Yasukouchi, Kazuo
• Format: Article
• Language: English
• ISSN: 0022-0728
• DOI: 10.1016/0022-0728(82)85021-3

Anodic bromination of anisole at a platinum electrode gave p-bromoanisole in high regio-selectivity; p-/ o-ratios were about 12 or more. The current efficiency for the bromination was ca. 80% at anode potentials of 1.3–1.8 V vs. Ag/Ag +. The ratio of the concentration of anisole to that of bromide ion, [Anisole]/[Br −] ratio, showed a pronounced effect on the current efficiency and p-/ o-isomer selectivity. and [Anisole]/[Br −] ratios 1̄0 were preferable. The effective potentials for the bromination were more positive than those of a new wave (III a) which developed by adding anisole to the solution containing bromide ion, while no appreciable bromination occurred when electrolyses were undertaken at the plateaux of the first and the second waves for oxidation of bromide ion. The bromination also occurred in the anisole/Br 2 system by passing electricity further. The limiting current of wave III a showed kinetic-controlled characteristics. Thus, the formation of an oxidizable intermediate which was formed by a reaction of anisole with Br 2 was proposed to be important, the bromination occurring efficiently via the electrochemical oxidation of the intermediate. No significant influence of the light on the bromination was observed. Neither dibromo derivatives nor side-chain brominated products were detected under the present experimental conditions.