Hydrogen Bromide → 3-Bromo-4-chlorothiophene

Participants

Reaction Steps

A catholyte of 650 ml of methanol, 0.5 g of lead acetate dihydrate, 0.5 g of tetrabutylammonium tetrafluoroborate, 20 ml of hydrogen bromide solution (48% in water) and 20 g of 3-chloro-2,4,5-tribromothiophene were electrolysed in electrolysis cell 1 at a current density of 100 mA/cm2 at the beginning and 25 mA/cm2 at the end of the batch, a voltage of 7.2 to 3.4 V and a temperature of 28° to 35° C. The current consumption was 8.8 Ah. After addition of 100 ml of water to the catholyte, extraction with CF2Cl--CFCl2 and removal of the solvent by distillation, 8.24 g of 4-bromo-3-chlorothiophene (yield: 73.8%), 0.665 g of 3-chlorothiophene (yield: 9.1%) and 0.4 g of dibromothiophene of unknown structure (yield: 2.9%) were obtained.

Provenance & Evidence