# Preparation of Bromoacetone

Ref: Organic Synthesis Collective Volume II, p 88-89 A 5-L, three-necked, round-bottomed flask is provided with an efficient mechanical stirrer, a 48-cm. Allihn reflux condenser, a thermometer, and a 500ml separatory funnel, the stem of which reaches nearly to the bottom of the flask. Through the separatory funnel are introduced 1.6 1. of water, 500ml of pure acetone, and 372 ml of glacial acetic acid. The stirrer is started and the temperature of the water bath is raised to 70-80°C, so that the mixture in the flask is at about 65°C. Then 354 ml (7.3 moles) of bromine is carefully added through the separatory funnel. The addition, which requires one to two hours, is so regulated as to prevent the accumulation of unreacted bromine As a rule the solution is decolorized in about twenty minutes after the bromine has been added. When the solution is decolorized, it is diluted with 800 ml of cold water, cooled to 10°C, made neutral to Congo red with about 1 kg. of solid anhydrous sodium carbonate, and the oil which separates is collected in a separatory funnel and dried with 80g of anhydrous calcium chloride. After drying, the oil is fractionated and the fraction boiling at 38-48°C/13 mmHg is collected. The yield is 470-480 g. (50-51% yield). If a purer product is desired, the above product is refractionated and the fraction boiling at 40-42°C/13 mmHg is collected. The yield is 400-410 g. (43-44% yield). The higher-boiling fraction contains a mixture of isomeric dibromoacetones.