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Org. Synth. 1922, 2, 93
DOI: 10.15227/orgsyn.002.0093
1,3,5-TRINITROBENZENE
[Benzene, 1,3,5-trinitro-]
Submitted by H. T. Clarke and W. W. Hartman.
Checked by J. B. Conant and J. J. Toohy.
1. Procedure
The crude trinitrobenzoic acid obtained by oxidation of 360 g. (1.6 moles) of trinitrotoluene (p. 543) is mixed with 2 l. of water at 35° (Note 1) in a 5-l. flask provided with a stirrer. Fifteen per cent sodium hydroxide solution is added, with continuous stirring, until a faint red color is just produced (Note 2). The color is then immediately discharged by means of one or two drops of acetic acid, and the liquid is filtered from unchanged trinitrotoluene. The filtrate is transferred to a 5-l. flask, and 70 cc. of glacial acetic acid is added.
The mixture is then gently heated (Note 3), with continuous stirring, when trinitrobenzene separates in crystalline condition and floats on the surface of the liquid as a frothy layer. After about one and one-half hours the evolution of gas ceases; at this point the crystals begin to stir into the solution. The heating and stirring are continued for three-quarters of an hour, when the mixture is allowed to cool, and the crystals filtered off. A sample of the filtrate should be tested for undecomposed trinitrobenzoic acid: if a precipitate is produced by the addition of sulfuric acid the process must be continued. After recrystallization from glacial acetic acid, the product melts at 121–122°. The yield is 145–155 g. (43–46 per cent of the theoretical amount calculated from the trinitrotoluene).
2. Notes
1. During the solution of the trinitrobenzoic acid, the temperature should not be below 35°, owing to the slight solubility of trinitrobenzoic acid in cold water. The heat of neutralization raises the temperature to 45–55°, but 55° should not be exceeded, since any trinitrobenzene formed at this point would later be removed with the unreacted trinitrotoluene.
2. Care must be taken that no more alkali is added than is just sufficient to produce the faint red color. If an excess of alkali is added it produces a permanent color, which is not removed by acid and colors the final product.
3. When once the evolution of carbon dioxide sets in, the flame must be cut down so as to avoid the formation of a thick layer of froth which might foam over.
3. Discussion
1,3,5-Trinitrobenzene can be prepared by nitrating m-dinitrobenzene,1 and by heating 2,4,6-trinitrobenzoic acid or its sodium salt with water, alcohol, dilute sodium carbonate, or other suitable solvent.2 2,4,6-Trinitrobenzaldehyde3 and 2,4,6-trinitrobenzoic acid4 both furnish trinitrobenzene on treatment with alcoholic ammonia—the yield from the aldehyde is reported to be quantitative.

References and Notes
  1. Hepp, Ber. 9, 402 (1876), Ann. 215, 344 (1882); Drummond, J. Soc. Chem. Ind. 41, 338T (1922).
  2. Chemische Fabrik Griesheim, Ger. pat. 77,353 [Frdl. 4, 34 (1894–97)], Desvergnes, Chimie & industrie, 25, 3, 291 (1931) [C. A. 25, 2699 (1931)], which contains a comparative study of methods of preparation.
  3. Secareanu, Bull. soc. chim. (4) 51, 596 (1932).
  4. Secareanu, ibid. 53, 1399 (1933).

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

2,4,6-trinitrobenzoic acid or its sodium salt

sulfuric acid (7664-93-9)

acetic acid (64-19-7)

ammonia (7664-41-7)

sodium hydroxide (1310-73-2)

sodium carbonate (497-19-8)

carbon dioxide (124-38-9)

1,3,5-Trinitrobenzene,
Benzene, 1,3,5-trinitro- (99-35-4)

2,4,6-Trinitrobenzoic acid (129-66-8)

trinitrotoluene (118-96-7)

trinitrobenzoic acid

trinitrobenzene

2,4,6-Trinitrobenzaldehyde (606-34-8)

m-dinitrobenzene (99-65-0)