In a
12-l. round-bottomed flask equipped with stirrer, dropping funnel, and efficient reflux condenser are placed
450 g. (5 moles) of urethan (m.p.
46–48°),
7.5 l. of dry ether, and
218 g. of sodium wire (Note
1) and (Note
2). The mixture is warmed, and evolution of
hydrogen accompanied by formation of sodium compound soon begins; after 2–3 hours the greater part of the metal will have been replaced by a gelatinous white precipitate. The stirrer is now started and the mixture warmed under reflux for an additional 2 hours. The flask is then cooled externally with running water, and
1050 g. (9.6 moles) of ethyl chlorocarbonate is added slowly over a period of 2 hours. The gelatinous precipitate becomes powdery, and the remainder of the
sodium dissolves. After all the ester has been added, the mixture is stirred overnight at room temperature and then filtered (Note
3). The white residue is washed with
1 l. of ether, and the
ether is removed from the combined solutions by evaporation on a
steam bath (Note
4). The residual oil is distilled; after a fore-run containing some
urethan, the product distils at
143–147° /12 mm. The yield is
575–640 g. (
51–57%). On redistillation, all the product boils at
146–147° /12 mm.