A
2-l. three-necked round-bottomed flask is fitted with a
mechanical stirrer and a
500-ml. dropping funnel (Note
1). The third neck is fitted with a
thermometer and a length of rubber tubing to lead evolved
hydrogen fluoride to the rear of the hood away from the operator. The flask is charged with
340 g. (2.09 moles) of crude 2-chloro-1,1,2-trifluoroethyl ethyl ether (p. 184) and cooled in an
ice bath until the temperature of the halo ether is below 5°. From the
dropping funnel,
228 ml. of 96% sulfuric acid (420 g., 4.1 moles) is added at such a rate that the temperature can be maintained at 5–15°. The addition requires 30–45 minutes, during which evolution of
hydrogen fluoride begins. The reaction mixture is stirred at 10° for 2 hours, then carefully poured onto a mixture of 1 kg. of crushed ice and 500 ml. of water. The product, a nearly white oil, settles out as the lower layer. It is separated, washed until free of acid with three
25-ml. portions of saturated sodium bicarbonate solution (Note
2), then with four 25-ml. portions of water, and dried over
10 g. of Drierite. The weight of crude dried ester is
200–210 g. (
68–71%). Fractional distillation gives
190–200 g. (
65–68% yield) of pure
ethyl chlorofluoroacetate, b.p.
129–130°,
nD25 1.3925 (Note
3).