Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

256 PHBNYLNITKOMBTHANB
8. PHENYLNITROMETHANE 1
(a) aCZ-PHENYLNITROACETONITRILE SODIUM
C6.H5.C.CN
II
NOONa
In a round-bottomed flask (capacity 0-5 1.) 8 g. of sodium are
dissolved in 120 c.c. of absolute alcohol. Into the solution, which
is kept cool in water (precipitation of ethoxide is not detrimental) a
mixture of 36 g. of benzyl cyanide (p. 137) and 32 g. of ethyl nitrate
(p. 148) is poured in small portions. The salt formulated above
separates gradually in the shape of almost colourless crystals. In
order to allow the reaction to proceed to completion, the flask is left
for one hour without cooling, but with exclusion of moisture ; the
precipitate is then collected at the pump and subsequently washed
first with alcohol-ether (1:1) and then with ether alone. Yield
40-45 g.
With ferric chloride solution a sample of the salt, dissolved in
alcohol, gives an intense olive-green colour.
(6) HYDROLYSIS TO THE SODIUM SALT OF
aci-PHENYLNITROMETHANE
The sodium salt just prepared (about 40 g.) is heated to gentle
boiling in an open round-bottomed flask on a conical air bath with
600 c.c. of 2iV-sodium hydroxide solution. The concentration of
the solution gradually increases and large amounts of ammonia are
evolved. The hydrolysis is complete when this evolution ceases.
The sodium salt of the acz-phenylnitromethane, which is sparingly
soluble in the excess of alkali, frequently begins to separate in
crystalline form even while the solution is hot. If this occurs before
the reaction has ceased, hot water is added and boiling is continued
until the evolution of ammonia is complete. Then the solution is
allowed to cool and, with continuous shaking and efficient ice-cooling,
is acidified with about 220 c.c. of rather concentrated hydrochloric
acid (110 c.c. each of concentrated acid and water). Sufficient acid
must be added to produce a distinct colour change on Congo paper
and to cause complete precipitation of the aa-nitro-compound which
1 W. Wislicenus and A. Endres, Ber., 1902, 35, 1757.