A solution of
sodium amide (0.226 mole) in
liquid ammonia is prepared in a
1-l. three-necked flask equipped with a
condenser, a
ball-sealed mechanical stirrer, and a
dropping funnel. Commercial anhydrous
liquid ammonia (500 ml.) is introduced from a cylinder through an
inlet tube. To the stirred
ammonia is added a small piece of
sodium. After the appearance of a blue color, a few crystals of
ferric nitrate hydrate (about 0.25 g.) are added, followed by small pieces of freshly cut
sodium until 5.2 g. has been added. After all the
sodium has been converted to the amide (Note
1),
14.2 g. (0.104 mole) of phenylacetic acid (Note
2) is added and the dark-green suspension is stirred for 15 minutes. To the green suspension is added rapidly
13.2 g. (0.104 mole) of benzyl chloride (Note
3) in
25 ml. of anhydrous ether, and the mixture is then stirred for 1 hour. The mixture is then evaporated to near dryness on a
steam bath,
200 ml. of ether added, and evaporation to dryness effected. Another
200 ml. of ether is added, followed by evaporation to dryness. The resulting solid is then dissolved in 300 ml. of water and washed with three
200-ml. portions of ether. The aqueous solution is filtered through a layer of Celite to remove the slight brown coloration, and the filtrate is acidified with
hydrochloric acid. A colorless oil forms which, when cooled for a few minutes in an
ice bath, becomes a white crystalline solid. This is collected by filtration and washed with three 100-ml. portions of hot water (Note
4) and dried. The yield of crude
α,β-diphenylpropionic acid, m.p.
92.0–93.5°, is
19.85 g. (
84.5–88%). The crude solid is recrystallized from
60 ml. of petroleum ether (
60–90°) to yield
18.80 g. (
80–84%) (Note
5) of
α,β-diphenylpropionic acid, m.p.
95.5–96.5° (Note
6) and (Note
7).