Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

344 BBNZOPHBNONB
benzene, 35 g. (0-25 mole) of benzoyl chloride, and 100 c.c. of pure
carbon bisulphide (or 70 c.c. more benzene). The flask is then
attached to a long reflux condenser and warmed on the water bath
at 50° until only small amounts of hydrogen chloride are being
evolved (2-3 hours). The solution acquires a deep brown colour.
The carbon bisulphide (or benzene) is now removed by distillation
through a downward condenser and the residue is cautiously poured,
while still warm, into a capacious flask containing 300 c.c. of water
and small pieces of ice. After rinsing out the reaction flask with a
little water and adding 10 c.c. of concentrated hydrochloric acid to
the reaction mixture, steam is passed through for about twenty
minutes. The material which remains in the flask is then cooled,
taken up in ether and shaken several times with dilute sodium
hydroxide solution. After the ethereal solution has been dried
with calcium chloride and the ether has been evaporated, the residue
is distilled from a flask with low side tube. Boiling point 297°.
Melting point 48°. Yield about 35 g. A purer product is obtained
by vacuum distillation in a sausage flask.
Benzophenone Oxime
To a solution of 4 g. of benzophenone in 25 c.c. of alcohol, cooled
solutions of 3 g. of hydroxylamine hydrochloride in 6 c.c. of water
and 5 g. of potassium hydroxide in 5 c.c. of water are added and the
whole is heated under reflux on the water bath for two hours. The
product is then poured into 50 c.c. of water, any unchanged ketone is
removed by nitration after shaking to cause aggregation, the filtrate
is faintly acidified with dilute sulphuric acid, and the free oxime
recrystallised from alcohol. Melting point 140°.
Beckmann Rearrangement to Benzanilide
A weighed quantity of the oxime is dissolved in some cold ether,
free from water and alcohol, and to the solution 1 -5 parts of finely
powdered phosphorus pentachloride are gradually added. The
ether is then removed by distillation and water is added to the
residue with cooling : the ensuing precipitate is recrystallised from
alcohol. Melting point 163°.
The interesting intramolecular rearrangement 1 which is brought
1 E. Beckmann, Ber., 1886, 19, 988; 1887, 20, 1507, 2580; Annalen, 1889,
252, 1, 44.