Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

348 QUINIZAKIN
the product acquires the consistency of porridge. It is kept cool
externally while 25 c.c. of ice-water are added, some ether is poured
in, and the ether layer is separated. The ketimine which is present
in the aqueous solution as hydrochloride is hydrolysed by boiling
the solution for half an hour. The resacetophenone crystallises from
the solution on cooling. Yield 4-5 g. It can be recrystallised from
water or alcohol. Melting point 145°.
6. QUINIZARIN FROM PHTHALIC ANHYDRIDE AND QUINOL 1
A mixture of 5 g. of pure quinol, 20 g. of phthalic anhydride,
50 c.c. of pure concentrated sulphuric acid, and 5 g. of boric acid is
heated in an open flask on an oil bath for three hours at 150°-160°,
and then for one hour at 190°-200°. While still hot the solution
is stirred into a porcelain basin containing 400 c.c. of water, then
heated to boiling and filtered hot at the pump. This operation is
repeated, and then the precipitate is boiled with 250 c.c. of glacial
acetic acid and filtered while hot at the pump. The filtrate is poured
into a beaker and diluted with an equal volume of hot water. The
crude quinizarin which separates on cooling is collected at the pump,
washed repeatedly with water, and dried, first on the water bath and
then in an oven at 120°. It is recrystallised from 150 c.c. of boiling
glacial acetic acid. Melting point 194°. The substance forms large
orange-yellow leaflets which, after collection at the pump, are washed
with a little glacial acetic acid and then with ether. Especially fine
crystals are obtained from toluene or xylene. Like alizarin, quinizarin
dissolves in alkalis with a deep violet colour. It can be sublimed
without decomposition. Yield 2-2-5 g.
Sections 3, 4, 5, 6: Theoretical Considerations
Both acid chlorides and alkyl chlorides react with aromatic compounds
in the presence of aluminium chloride, zinc chloride, or ferric
chloride in such a way that HC1 is eliminated and the acyl or alkyl group
enters the ring :
CI.CO.CH, —> r i co.cn3 +HC1
+HCI
1 Grimm, Ber., 1873, 6, 506 ; Baeyer, Ber., 1875, 8, 152. Liebermann, Annalen,
1882, 212, 10 ; G.P. 255,031 (Friedlander, XI, 588).