Hydrogen Bromide → 1-(3-Bromo-4-methylphenyl)ethan-1-one

Participants

Reaction Steps

Anhydrous aluminum chloride (30 g, 225 mmol) was added to a 100 mL 2-neck round-bottom flask equipped with a magnetic stirrer, a septum, and a pressure-equalizer dropping funnel. The flask was flushed with nitrogen through the septum. 4-Methylacetophenone (13.3 mL, 100 mmol) was added to the flask via the dropping funnel over a period of 10 min. After the mixture was stirred for additional 30 min, bromine (5.7 mL, 110 mmol) was added dropwise over a period of 5 min. The reaction was completed when the reaction mixture solidified and no more hydrogen bromide was generated. The solidified mixture was transferred portionwise to a 3N aqueous HCl solution (250 mL). The dark oil at the bottom of the solution was extracted by ether (3×30 mL). The organic layer was then washed by a saturated NH4Cl aqueous solution (50 mL), dried over with anhydrous magnesium sulfate, and concentrated to get a crude product. The crude product was further purified by distillation under reduced pressure (118° C., 3 mm Hg) to give 18.53 g (87% yield) of the desired product. m.p. 94–95° C.; 1H NMR (300 MHz, CDCl3) δ 2.46 (3H, s), 2.58 (3H, s), 7.33 (1H, d, J=4.7 Hz), 7.79 (1H, dd, J=4.7, 0.99 Hz), 8.12 (1H, d, J=0.99 Hz); 13C NMR (75 MHz, CDCl3) δ 23.19, 26.52, 123.21, 127.08, 130.87, 132.32, 136.46, 143.53, 196.4; IR (neat) 3024 (s), 1684 (s), 1599 (m), 1383 (m), 1521 (s), 1039 (m), 958 (w), 907 (m), 831 (w) cm−1; MS m/z 212 (M+), 199, 197, 171, 169, 89; HRMS calcd.: C9H9OBr 211.9837, found: 211.9840.

Provenance & Evidence