- In a 1 -litre two-necked round-bottomed flask, equipped with a dropping funnel and a double surface reflux condenser to which is attached a gas absorption trap, place 220g (135 ml, 1.86 mol) of redistilled thionyl chloride, and heat to boiling.
- Add 125g (126 ml, 1.69 mol) of pure propanoic acid at such a rate that the mixture refluxes gently (c. 1 hour).
- Reflux the mixture for a further 30 minutes to expel the dissolved sulphur dioxide, allow to cool and add 0.5 g of purified red phosphorus.
- Introduce 310 g (100 ml, 1.93 mol) of dry bromine during 5-7 hours to the gently boiling propanoyl chloride, and then reflux the mixture for 7 hours, by which time the evolution of hydrogen bromide almost ceases.
- Add the crude 2-bromopropanoyl chloride during 2 hours to 250 ml of absolute ethanol contained in a three-necked round-bottomed flask, equipped with a mechanical stirrer and a reflux condenser.
- Complete the reaction by heating on a water bath for 4 hours, when hydrogen chloride is slowly evolved.
- Filter the reaction liquid into 500 ml of distilled water, separate the oil and wash it successively with water, sodium hydrogen carbonate solution and water.
- Dry over calcium sulphate and distil at normal pressure to remove the low b.p. fraction (largely ethyl bromide: 75 g) and then under diminished pressure.
- Collect the ethyl 2-bromopropanoate as a colourless liquid at 69-70 °C/25mmHg; the yield is 221 g (72%).
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