Org. Synth. 1947, 27, 91
DOI: 10.15227/orgsyn.027.0091
1,3,5-TRIACETYLBENZENE
[Benzene, 1,3,5-triacetyl]
Submitted by Robert L. Frank and Robert H. Varland.
Checked by Arthur C. Cope and W. H. Jones.
1. Procedure
Sixty-nine grams (3.0 gram atoms) of freshly cut sodium is placed in a 1-l. round-bottomed flask with 400 ml. of dry xylene (Note 1) and heated until all the sodium is melted. The flask is closed with a rubber stopper and shaken vigorously to form finely powdered sodium (Note 2). When cool, the contents are transferred to a 5-l. three-necked round-bottomed flask, and the xylene is decanted. The powdered sodium is then washed with two 100-ml. portions of anhydrous ether by decantation, after which 1 l. of anhydrous ether is added. The flask is placed on a steam bath and fitted with a Hershberg stirrer, an upright condenser, and a 500-ml. dropping funnel. The condenser and funnel are protected from moisture by calcium chloride tubes. Through the dropping funnel is then added with stirring 138 g. (175 ml., 3.0 moles) of absolute ethanol at such a rate that gentle refluxing occurs. The mixture is refluxed and stirred for 6 hours after the addition is complete.
The reaction mixture is diluted with 1.5 l. of anhydrous ether, and a mixture of 174 g. (220 ml., 3.0 moles) of acetone (Note 3) and 222 g. (241 ml., 3.0 moles) of ethyl formate (Note 4) is placed in the dropping funnel and added to the flask over a period of 2 hours. Stirring is continued for 2 hours after the acetone and ethyl formate have been added (Note 5).
The reaction mixture is then rapidly extracted with five 1-l. portions of water (Note 6). Acetic acid is added to the water solution until it is acid to litmus. The acidified solution is warmed to 50° on a steam bath and maintained at approximately that temperature for 2 hours. It is subsequently allowed to stand at room temperature for 48 hours, during which time the triacetylbenzene crystallizes.
The crude yellow crystalline solid (m.p. in the range 150–162°) is collected on a filter; the yield is 84–94 g. (41–46%). It is recrystallized by dissolving in hot ethanol (18 ml. of ethanol per gram), adding 2 g. of Norit, filtering through a steam-heated funnel (Note 7), and cooling the filtrate in an ice bath. The yield of shiny white crystals, m.p. 162–163°, is 62–79 g. (30–38%) (Note 8).
2. Notes
1.
The first portion of this synthesis is very similar to the preparation of
acetylacetone by the method of Adkins and Rainey
(p. 17). The procedure and
(Note 1),
(Note 2),
(Note 3),
(Note 4),
(Note 5),
(Note 6) and
(Note 8) for that synthesis may therefore be helpful in the present preparation.
2.
A more finely powdered
sodium can be obtained if paraffin oil ("Stanolind") is used in place of
xylene (Gilbert Ashburn, private communication).
3.
Acetone dried over
calcium sulfate and distilled from
phosphorus pentoxide is satisfactory.
4.
The
ethyl formate is dried over
calcium sulfate and distilled.
5.
If the solution becomes so thick as to make stirring difficult, it is advisable to add more anhydrous
ether.
6.
It is important that the extraction and acidification be carried out without delay. Oxidation of the intermediate product takes place readily on exposure to air and causes the solution to become dark in color.
7.
If a steam-heated funnel is not used, a larger volume of
ethanol should be employed to prevent crystallization during filtration.
8.
The higher yield (
38%) was obtained if the commercial absolute
ethanol was dried by treatment with
sodium and
ethyl phthalate.
1
3. Discussion
Triacetylbenzene has been prepared only by the condensation of
acetone with
ethyl formate followed by the trimerization of the intermediate
acetylacetaldehyde.
2,3
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
ethanol (64-17-5)
acetic acid (64-19-7)
ether (60-29-7)
calcium sulfate (7778-18-9)
acetone (67-64-1)
Norit (7782-42-5)
sodium (13966-32-0)
xylene (106-42-3)
ethyl formate (109-94-4)
ethyl phthalate
Acetylacetone (123-54-6)
acetylacetaldehyde
1,3,5-Triacetylbenzene,
Benzene, 1,3,5-triacetyl (779-90-8)
triacetylbenzene
phosphorus pentoxide (1314-56-3)
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