Organic Syntheses | Page 7

Am. Pharm. Assoc. 11, 599 (1922).

III
BENZYL CYANIDE
C6H5CH2Cl + NaCN--> C6H5CH2CN + NaCl
Prepared by ROGER ADAMS and A. F. THAL Checked by O.
KAMM and A. O. MATTHEWS.
1. Procedure
IN a 5-l. round-bottom flask, fitted with a stopper holding a reflux
condenser and separatory funnel, are placed 500 g. of powdered sodium
cyanide (96-98 per cent pure) and 450 cc. of water. The mixture is
warmed on a water bath in order to dissolve most of the sodium
cyanide, and then 1 kg. of benzyl chloride (b. p. 170-180'0) mixed with
1 kg. of alcohol is run in through the separatory funnel in the course of

one-half to three-quarters of an hour. The mixture is then heated with a
reflux condenser on the steam bath for four hours, cooled and filtered
with suction to remove most of the sodium chloride. It is well to wash
the filtered salt with a small portion of alcohol in order to remove any
benzyl cyanide which may have been mechanically held. The flask is
now fitted with a condenser, and as much alcohol as possible is
distilled off on the steam bath. The residual liquid is cooled, filtered if
necessary, and the layer of benzyl cyanide separated. This crude benzyl
cyanide is now placed in a Claisen distilling flask and distilled in vacuo,
the water and alcohol coming over first, and finally the cyanide. It is
advantageous to use a fractionating column or, better still, a Claisen
flask with a modified side-arm[1] (Vol. I, p. 40, Fig. 3) which gives the
same effect as a fractionating column. The material is collected from
135-140'0/38 mm. (115-120'0/10 mm.). The yield is 740-830 g. (80-90
per cent of the theoretical amount).
[1] J. Am. Chem. Soc. 39, 2718 (1917). 2. Notes
The quality of the benzyl chloride markedly affects the yield of pure
benzyl cyanide. If a poor technical grade is used, the yields will not be
more than 60-75 per cent of the theoretical, whereas consistent results
of about 85 per cent or more were always obtained when a product was
used that boiled over 10'0. The technical benzyl chloride at hand
yielded on distillation about 8 per cent of high-boiling material; a
technical grade from another source was of unusual purity and boiled
over a 2'0 range for the most part.
It is advisable to distil off the last portion of alcohol and water in vacuo
and also to distil the benzyl cyanide in vacuo, since under ordinary
pressures a white solid invariably separates during the distillation.
One method of purifying the benzyl cyanide is to steam distil it after
the alcohol has been first distilled from the reaction mixture. At
ordinary pressures, this steam distillation is very slow and, with an
ordinary condenser, requires eighteen to twenty hours in order to
remove all of the volatile product from a run of 500 g. of benzyl
chloride. The distillate separates into two layers; the benzyl cyanide
layer is removed and distilled. The product obtained in this way is very
pure and contains no tarry material, and, after the excess of benzyl
chloride has been removed, boils practically constant. This steam
distillation is hardly advisable in the laboratory.

The benzyl cyanide, prepared according to the procedure as outlined, is
collected over a 5'0 range. It varies in appearance from a colorless to a
straw-colored liquid and often develops appreciable color upon
standing. For a product of special purity, it should be redistilled under
diminished pressure and collected over a 1-2'0 range. For most
purposes, such as the preparation of phenylacetic acid or ester, the
fraction boiling 135-140'0/38 mm. is perfectly satisfactory. 3. Other
Methods of Preparation
Benzyl cyanide occurs naturally in certain oils.[1] The only feasible
method of preparing it that has been described in the literature is the
one in which alcoholic potassium cyanide and benzyl chloride[2] are
employed. The cheaper sodium cyanide is just as satisfactory as the
potassium cyanide and therefore is the best material to use. Gomberg
has recently prepared benzyl cyanide from benzyl chloride and an
aqueous solution of sodium cyanide.[3]
[1] Ber. 7, 519, 1293 (1874); 32, 2337 (1899)
[2] Ann. 96, 247 (1855); Ber. 3, 198 (1870); 14, 1645 (1881); 19, 1950
(1886).
[3] J. Am. Chem. Soc. 42, 2059 (1920).

IV
a, g-DICHLOROACETONE
CH2ClCHOHCH2Cl + O(Na2Cr2O7 + H2SO4)--> CH2ClCOCH2Cl +
H2O
Prepared by J. B. CONANT and O. R. QUAYLE. Checked by A. W.
DOX, L. YODER, and O. KAMM.
1. Procedure
IN a 2-l. flask are placed 375 g. of commercial sodium dichromate, 225
cc. of water, and 300 g. of dichlorohydrin (b. p. 68-75'0/14 mm.). The
flask is set in a water bath and equipped with a thermometer and
mechanical stirrer. The contents are vigorously stirred, and 450 g. of
sulfuric acid,