C.
α-Chlorophenylacetic acid. A solution of
119 g. (0.6 mole) of ethyl α-chlorophenylacetate in
238 ml. of glacial acetic acid and
119 ml. of concentrated hydrochloric acid, contained in a
1-l. round-bottomed flask, is heated under reflux in a hood for 1.5 hours (Note
6). At the end of the heating period the solution is concentrated by heating in an
oil bath at 100° at reduced pressure (15–20 mm.) until no further material is distilled (Note
7). The residue is allowed to cool to room temperature and poured slowly, with stirring, into 1-l. of ice-cold saturated
sodium bicarbonate solution contained in a
2-l. beaker. Solid
sodium bicarbonate is added in small portions until the solution becomes neutral to universal indicator paper (Note
8). The solution is then extracted with two
200-ml. portions of ether in a 2-l. separatory funnel (Note
9), (Note
10). The aqueous phase is placed in a
3-l. beaker and acidified cautiously with ice-cold 12
N sulfuric acid until the mixture is acid to Congo red paper (Note
11). The oily suspension is extracted with two
200-ml. portions of ether in a 2-l. separatory funnel. The
ether extracts are washed with two 100-ml. portions of water and dried over
45 g. of anhydrous sodium sulfate. The dried
ether extract is transferred to a
1-l. Erlenmeyer flask and concentrated on a
steam bath until
ether is no longer distilled. To the residue there is added
500 ml. of warm (50–60°) concentrated hydrochloric acid (in a hood), and the suspension is allowed to cool with occasional swirling (Note
12). Crystallization is completed by chilling in ice, and the product is collected on a
sintered-glass funnel. After the product has been dried as much as possible on the funnel it is dried to constant weight in a
vacuum desiccator over
solid potassium hydroxide. The yield of dry acid is
82–84 g. (
80–82%), m.p.
77.5–79.5°. It is satisfactory for most purposes. If very pure material is desired the acid may be recrystallized from
three volumes of hexane to give material, m.p.
78.5–79.5°, in
90–95% recovery.