Org. Synth. 1938, 18, 15
DOI: 10.15227/orgsyn.018.0015
α-CHLOROANTHRAQUINONE
[Anthraquinone, 1-chloro-]
Submitted by W. J. Scott and C. F. H. Allen.
Checked by Louis F. Fieser and E. B. Hershberg.
1. Procedure
A
2-l. three-necked flask fitted with a
stirrer (Note 1) and
(Note 2),
condenser, and
dropping funnel (Note 3) is mounted in the
hood, and in it are placed
20 g. (0.061 mole) of potassium anthraquinone-α-sulfonate (p. 539), 500 cc. of water, and
85 cc. (1 mole) of concentrated hydrochloric acid. The solution is heated to boiling and stirred, while a solution of
20 g. (0.19 mole) of sodium chlorate (Note 4) in 100 cc. of water is added dropwise over a period of three hours
(Note 5). The mixture is refluxed very slowly for an additional hour before the precipitated
α-chloroanthraquinone is collected by suction filtration and washed free from acid with hot water (about 350 cc.). After drying
in vacuo at 100°, the bright yellow product melts at
158–160° (corr.) and weighs
14.6–14.7 g. (
97–98 per cent of the theoretical amount)
(Note 6) and
(Note 7).
2. Notes
1.
Since the mixture tends to foam toward the end of the reaction, it is advisable to use an effective stirrer. A
Hershberg stirrer (p. 117) of tantalum wire gave good service in the hands of the checkers; the metal was not appreciably attacked after repeated use.
3.
Since the usual dropping funnel has the disadvantage of requiring considerable attention from the operator, the checkers found it much more convenient to employ the device (of E. B. H.) shown in
Fig. 5.
Fig. 5
4.
Potassium chlorate is less satisfactory because of its lower solubility.
5.
If the addition is too rapid or the boiling too vigorous, chlorinating gases are lost through the condenser.
6.
Crystallization of the product from
200 cc. of n-butyl alcohol gives
13.4 g. of material in the form of yellow needles, m.p.
161–162° (corr.). Larger amounts are conveniently crystallized from
toluene, using 2 cc. per gram.
7.
The melting point given for highly purified
α-chloroanthraquinone is
162.5° (corr.). The possible contaminants include the β-isomer,
1,5-, and 1,8-dichloroanthraquinone, all of which melt at higher temperatures but depress the melting point of the α-monochloro compound.
3. Discussion
α-Chloroanthraquinone has been prepared from
α-aminoanthraquinone by the diazo reaction,
1 by the action of
thionyl chloride on
potassium anthraquinone-α-sulfonate under pressure,
2 and by the above process.
3
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
1,5-, and 1,8-dichloroanthraquinone
hydrochloric acid (7647-01-0)
thionyl chloride (7719-09-7)
mercury (7439-97-6)
n-butyl alcohol (71-36-3)
toluene (108-88-3)
sodium chlorate (7775-09-9)
potassium chlorate (3811-04-9)
α-Chloroanthraquinone,
Anthraquinone, 1-chloro- (82-44-0)
Potassium anthraquinone-α-sulfonate (30845-78-4)
α-aminoanthraquinone (82-45-1)
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