In a
4-l. beaker, equipped with a
powerful mechanical stirrer which reaches nearly to the bottom, are placed 500 ml. of water and
50 g. of mercuric chloride. The stirrer is started, and
200 g. (3.06 gram atoms) of zinc dust (Note
1) is rapidly sifted into the suspension. Stirring is continued until the
mercuric chloride dissolves (about 20–30 minutes). The
zinc is then allowed to settle, the supernatant liquid is removed by decantation, and the amalgam is filtered and washed with 200 ml. of water. The
zinc amalgam is returned to the beaker, which is now surrounded by an
ice bath, and
500 ml. of 95% ethanol and
100 g. (0.48 mole) of benzoin are added. The stirrer is started, and
500 ml. of concentrated hydrochloric acid is added through a dropping funnel at such a rate that addition is complete in about 2 hours; throughout the reaction the temperature is maintained below 15°. Stirring is continued for about 2 hours more.
About 2 l. of cold water is added to the reaction mixture, and the insoluble material is collected on a
Büchner funnel. The precipitate is transferred to a
2-l. beaker and extracted with two
600-ml. portions of hot ethanol. The combined extracts, on cooling, deposit long needles of
stilbene which weigh
55–59 g. and melt at
116–121°. These are filtered with suction and are recrystallized from
600 ml. of 95% ethanol. The yield is
45–48 g. (
53–57%) of colorless needless melting at
123–124°.