1,2-dichloroethane, commercial, 98%

Aluminium chloride, Lab reagent, 98%

Benzaldehyde, commercial, 97.5%

Sodium carbonate, Lab grade

Bromine- 98%, commercial

To a clean 2 l 4 necked flask carrying calcium chloride guard tube, thermometer pocket and a mechanical stirrer, was charged Dichloroethane (500 mL) followed by anhydrous aluminium chloride (177 g, 1.32 mol) under stirring. To this benzaldehyde (104 g, 1 mol) was added over a period of 1 h at 38-40 oC. After this bromine (176 g, 56.8 mL, 1.1 mol) was added over a period of 2 h at about 40 oC and further the mixture was stirred at the same temperature for 2 h. The reaction mass was quenched to approximately 1 kg crushed ice and stirred for 10 min. The organic layer separated was removed and washed with water ( 1000 mL) and 300 mL sodium carbonate solution(5%) followed by water (750 mL). The organic layer thus obtained was concentrated to get about 200 g residue. This residue was distilled under vacuum to get 160 g of pure 3-bromo benzaldehyde (Yield: 87%).

1. Benzaldehyde purity should be above 97% to get good reaction. Presence of more benzoic acid gives low yield.

2. 1,2-Dichloroethane is toxic and therefore the reaction should be carried out in efficient hood.

3. If the aluminium chloride is not good (old stock), this gives low yield.

 

1H NMR (90 MHz): δ 9.95 (1H), 8.20-7.15 (3 multiplets, 4H)

13C NMR ( 75 MHz): δ 190.50, 137.96, 137.15, 12.13, 130.58, 128.30, 123.27.

FTIR (neat): 1708, 1191, 676 cm -1

 

Shinichi Matsuura, Osamu Miyano, USPatent No: 4,945,186 (1990)