Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

ALANINB 229
rfZ-mandelic acid. However, a feebly laevo-rotatory preparation is
obtained as follows : The filtrate A is treated as has just been described
for pure cinchonine rf-mandelate, and the free acid thus
obtained must be laevo-rotatory since part of ^-modification has
been removed.
Of the three products so obtained, namely : (1) inactive racemic
acid, (2) pure rf-acid, and (3) impure Z-acid, aqueous solutions of
suitable concentration should be prepared. The rotations of the
solutions should then be determined with a polarimeter.
If cinchonine d-mandelate is not available a specimen suitable for
the inoculation in the first experiment is prepared as follows : To a few
cubic centimetres of the solution (a) saturated aqueous sodium chloride
solution is added drop by drop until slight precipitation occurs. The
mixture is then heated until the precipitated material has dissolved,
after which the solution is allowed to stand until crystals have been
deposited, which may require a day. The "crystals consist of cinchonine
hydrochloride on which a small amount of cinchonine d-mandelate
is deposited, enough, however, to induce the separation of further
quantities of the d-salt.
7. ALANINE 1
Freshly distilled acetaldehyde (13-2 g. ; 0-3 mole) dissolved in
100 c.c. of ether is poured into a pressure bottle containing a cold
saturated aqueous solution of 18 g. of ammonium chloride ; then
a solution of 20 g. of sodium cyanide in 30 c.c. of water is added
slowly drop by drop from a tap funnel with shaking and ice-cooling.
The closed bottle is then agitated at ordinary temperature for three
hours on a shaking machine. The contents of the bottle are next
transferred to a round-bottomed flask (capacity 0-51.) which is kept
cool in ice, while 100 c.c. of concentrated hydrochloric acid are added
in small portions. (Fume chamber ! Free hydrocyanic acid !)
The ether is removed by distillation through a downward condenser
and the aqueous solution, after being heated for one hour longer on
the boiling water bath, is transferred to a basin and evaporated to
dryness. (A brown colour develops in the aqueous solution after the
ether has been removed.) When the material in the basin is completely
dry and free from hydrochloric acid (test the odour) it is
extracted twice with 100 c.c. of boiling alcohol in a small roundbottomed
flask. The filtered alcoholic extracts are evaporated to
1 A. Strecker, Annalen, 1850, 75, 30; Zelinsky and Stadnikov, Ber., 1908,
41, 2061.