SYNTHESIS OF BENZHYDROL (DIPHENYLMETHANOL)
- In a 1 -litre three- necked flask,
equipped with a reflux condenser, a mechanical stirrer and a thermometer dipping into
the reaction mixture, place 50 g (0.275 mol) of benzophenone, 500 ml of rectified
spirit, 50 g of sodium hydroxide and 50 g (0.76 mol) of zinc powder.
- Stir the mixture; the temperature
slowly rises to about 70 °C.
- After 3 hours, when the temperature
has commenced to fall, filter the reaction mixture with suction and wash the residue
twice with 25 ml portions of hot rectified spirit.
- Do not allow the residual zinc powder
to become dry as it is flammable.
- Pour the filtrate into 2 litres of
ice water acidified with 100 ml of concentrated hydrochloric acid.
- The benzhydrol separates as a white
crystalline mass.
- Filter at the pump and dry in the
air.
- The yield of crude benzhydrol, m.p.
65 °C, is 49 g.
- Recrystallise from 50 ml of hot
ethanol and cool in a freezing mixture of ice and salt.
- Collect the colourless crystals and
dry in the air; 36 g of pure benzhydrol, m.p. 68 °C, are obtained.
- Dilute the mother-liquor with water to precipitate the residual benzhydrol,
and recrystallise this from a small quantity of hot alcohol.
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