A Suspension of
lithium amide (0.25 mole) (Note
1) 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. In the preparation of this reagent 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
clean lithium metal. 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
lithium metal (Note 2) until 1.73 g. has been added. After all the
lithium has been converted to the amide (Note
3),
17.6 g. (0.2 mole) of ethyl acetate (Note
4) is added, and the gray suspension is stirred for about 30 seconds. To the gray suspension is added
36.4 g. (0.2 mole) of benzophenone (Note
4) dissolved in
100 ml. of anhydrous ether. The mixture is stirred for 30 minutes and is then neutralized by the addition of
13.4 g. (0.25 mole) of ammonium chloride. The liquid
ammonia is then removed by use of a
steam bath while
200–300 ml. of ether is being added (Note
5). When the
ammonia has been removed, 200 ml. of cold water is added. The
ether layer is separated, and the aqueous layer is further extracted with two
100-ml. portions of ether. The combined
ether extract is dried over
magnesium sulfate and filtered, and the solvent is evaporated. The residue is dissolved in
50 ml. of hot 95% ethanol, treated with
Norit®, filtered, and allowed to cool. The yield of
ethyl β-hydroxy-β,β-diphenylpropionate, obtained as colorless, needle-like crystals melting at
85–86°, is
40.5–45.5 g. (
75–84%). The filtrate, on reduction in volume and cooling, yields small amounts of
benzophenone, m.p.
46–47°.