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13.8 g (0.6 mole) of sodium are dissolved in 250 ml of anhydrous ethanol. 61.2 g (0.46 mole) of diethyl malonate and 47.3 g of isopropyl urea (0.46 mole) are added to the resulting solution. The mixture thus formed is heated for 7.5 hours to 120° C. (temperature of the bath). After cooling, a solution of concentrated HCl and water (1:4) is slowly added until the precipitate formed during the reaction has dissolved. The resulting solution is evaporated until a precipitate appears and is then left standing at 0° C. The precipitate is then filtered, washed with cold water and dried, giving 75 g of colourless crystals.

1. customThe mixture thus formed
2. temperatureis heated for 7.5 hours to 120° C. (temperature of the bath)
3. temperatureAfter cooling
4. customformed during the reaction
5. dissolutionhas dissolved
6. customThe resulting solution is evaporated until a precipitate
7. waitis then left
8. customstanding at 0° C
9. filtrationThe precipitate is then filtered
10. washwashed with cold water
11. customdried