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Org. Synth. 1933, 13, 32
DOI: 10.15227/orgsyn.013.0032
1,4-DIBENZOYLBUTANE
[1,6-Hexanedione, 1,6-diphenyl-]
Submitted by Reynold C. Fuson and Joseph T. Walker.
Checked by W. H. Carothers and W. L. McEwen.
1. Procedure
One mole (146 g.) of adipic acid (Org. Syn. Coll. Vol. I, 1941, 18), previously dried over sulfuric acid in a vacuum, is placed in a 1-l. round-bottomed flask equipped with a condenser, and 357 g. (217 cc., 3 moles) of thionyl chloride is added at once. The mixture is heated gently on a water bath held at a temperature of 50–60°. After about four hours, solution is complete and evolution of hydrogen chloride has ceased. The flask is now connected to a downward condenser and heated under diminished pressure by a water bath to remove any excess thionyl chloride. The light yellow residue of adipyl chloride is ready for use.
A mixture of 300 g. (2.25 moles) of anhydrous aluminum chloride and 1.5 l. (17 moles) of benzene (dried over sodium and distilled) is placed in a 3-l. three-necked flask equipped with a mercury-sealed stirrer, a reflux condenser, and a dropping funnel. The reaction mixture is cooled in an ice bath, and, with rapid stirring, the adipyl chloride is added through the dropping funnel at an even rate during the course of forty-five minutes (Note 1). The reaction mixture darkens slowly but does not become black. After the adipyl chloride has been added, the ice bath is removed and stirring is continued for two hours at room temperature (Note 2).
The solution is then poured slowly, with constant stirring, into a mixture of 1 kg. of cracked ice and 200 cc. of concentrated hydrochloric acid in a 5-l. flask. There should be a small quantity of ice remaining after decomposition is complete. When the ice has melted, the mixture of water, precipitated dibenzoylbutane, and benzene is divided into two equal portions, and 1–1.25 l. of benzene is added to each. The solid is dissolved by shaking and gentle warming on the steam bath; the benzene layers are separated and washed, first with an equal volume of dilute sodium carbonate solution, and then with water.
The benzene solution is placed in a 5-l. flask, and 3–3.5 l. of benzene is removed by distillation. The residual liquid is set aside and allowed to cool. The dibenzoylbutane which crystallizes after several hours is filtered; it melts at 104–107° (Note 3). An equal volume of ether is added to the light brown filtrate, and a second crop of crystals is obtained (Note 4).
The yield of crude product is 199–216 g. (75–81 per cent of the theoretical amount). The material may be recrystallized by dissolving it in 1 l. of hot 95 per cent ethyl alcohol. Upon cooling, crystals which melt at 106–107° separate. The yield of recrystallized product is 190–210 g.
2. Notes
1. It is very important to keep the reaction mixture cold during the addition of the acid chloride; otherwise there will be charring which will lead to a discolored product.
2. If the reaction mixture is allowed to stand at this point the yield is materially decreased.
3. The melting point and color of the crude product seem to be influenced by the quality of the aluminum chloride. The checkers used a very pure aluminum chloride and found that the color of the reaction mixture was never darker than a bright orange, that the crude product was always colorless, and that the crude product always melted at 106–108°. If a less pure aluminum chloride is used the crude product is sometimes brown. This color may be completely removed by washing with a few cubic centimeters of cold ether, in which the diketone is only slightly soluble.
4. The checkers found that only 5–6 g. of material was precipitated by the addition of ether. For this reason it seems scarcely worth while to carry out this part of the procedure.
3. Discussion
Dibenzoylbutane has been prepared by the action of aluminum chloride on a mixture of benzene and adipyl chloride1 or benzene and polymeric adipic anhydride.2 It has also been obtained from adiponitrile and phenylmagnesium bromide,3 and as a by-product in the action of zinc on α,β-dibromopropiophenone4 and α,α'-dibromodibenzoylbutane.5 Melting points between 102°1 and 112°4 have been recorded for the diketone.
This preparation is referenced from:

References and Notes
  1. Etaix, Ann. chim. phys. (7) 9, 372 (1896).
  2. Hill, J. Am. Chem. Soc. 54, 4105 (1932).
  3. Compère, Bull. soc. chim. Belg. 44, 523 (1935).
  4. Kohler, Am. Chem. J. 42, 384 (1909).
  5. Fuson and Farlow, J. Am. Chem. Soc. 56, 1593 (1934).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

ethyl alcohol (64-17-5)

sulfuric acid (7664-93-9)

hydrogen chloride,
hydrochloric acid (7647-01-0)

Benzene (71-43-2)

ether (60-29-7)

thionyl chloride (7719-09-7)

Adipic acid (124-04-9)

sodium carbonate (497-19-8)

aluminum chloride (3495-54-3)

zinc (7440-66-6)

sodium (13966-32-0)

Phenylmagnesium bromide (100-58-3)

1,4-Dibenzoylbutane,
1,6-Hexanedione, 1,6-diphenyl- (3375-38-0)

adipyl chloride (111-50-2)

dibenzoylbutane

adipic anhydride

adiponitrile (111-69-3)

α,β-dibromopropiophenone

α,α'-dibromodibenzoylbutane