- Hydrolyse 108g (0.5 mol) of diethyl s-butylmalonate (1) with aqueous ethanolic potassium hydroxide solution following the procedure described for the hydrolysis of diethyl proplymalonate.
- Transfer the dried ether extract of the product to a 1-litre three-necked flask fitted with a sealed stirrer unit, an efficient reflux condenser and a dropping funnel charged with 80g (26 ml, 0.5 mol) of bromine.
- Stir the solution, add about 2-3 ml of bromine, and when this has reacted completely drop in the remainder of the bromine at such a rate that the ether refluxes gently.
- When all the bromine has reacted, add 100 ml of water cautiously from the dropping funnel to decompose any acyl bromide.
- Separate the ether layer, dry it over anhydrous sodium sulphate and remove the ether (rotary evaporator).
- Decarboxylate the residue by heating it for 5 hours in an oil bath maintained at 130°C and then distil the resulting bromo acid under reduced pressure, collecting the fraction of b.p. 125-140 °C/20mmHg. The yield is 65g (67%).
Notes to keep in mind:
1. Diethyl s-butylmalonate, b.p. 110-120°C/20mmHg, is
prepared by reacting 2-bromobutane with diethyl malonate.
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