Org. Synth. 1938, 18, 15
DOI: 10.15227/orgsyn.018.0015
[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.
2. Although a glass sleeve for the stirrer is fairly satisfactory, it is better to use a seal of the conventional type (Org. Syn. Coll. Vol. I, 1941, 33, Fig. 2a) filled with water rather than mercury.
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
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

References and Notes
  1. Bayer and Company, Ger. pat. 131,538 [Frdl. 6, 311 (1900–02)]; Groggins, "Unit Processes in Organic Syntheses," p. 175, McGraw-Hill Book Company, New York, 1935.
  2. Meister, Lucius, and Brüning, Ger. pat. 267,544 (Chem. Zentr. 1914, I, 89).
  3. Bayer and Company, Ger. pat. 205,195 (Chem. Zentr. 1909, I, 414); Badische Anilin- und Soda-Fabrik, Ger. pat. 228,876 (Chem. Zentr. 1911, I, 102); Ullmann and Ochsner, Ann. 381, 1 (1911).

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)

Anthraquinone, 1-chloro- (82-44-0)

Potassium anthraquinone-α-sulfonate (30845-78-4)

α-aminoanthraquinone (82-45-1)