Organic Syntheses

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Author: Unknown

XXIV 1,3,5-Trinitrobenzene

C6H2(NO2)3CO2H—> C6H3(NO2)3 + CO2

Prepared 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. of trinitrotoluene (prep. XXV, p. 95) is mixed with 2 l. of water at 35’0 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. (See Notes.) The color is then immediately discharged by means of one or two drops of acetic acid, and the liquid is filtered from unchanged trinibrotoluene. The filtrate is transferred to a 5-l. flask, and 70 cc. of glacial acetic acid are added. The mixture is then gently heated, 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 a half hours the evolution of gas ceases; at this point the crystals begin to stir into the solution. The heating and stirring is 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 121-122’0. The yield is 145-155 g. (43 to 46 per cent of the theoretical amount calculated from the trinitrotoluene). 2. Notes

During the solution of the trinitrobenzoic acid, the temperature should not be below 35’0, owing to the slight solubility of trinitrobenzoic acid in cold water. The heat of neutralization raises the temperature to 45-55’0, but the latter temperature should not be exceeded, since any trinitrobenzene formed at this point would later be removed with the unreacted trinitrotoluene.

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.

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. Other Methods of Preparation

1,3,5-Trinitrobenzene can be prepared by heating -dinitrobenzene with nitric acid and sulfuric acid to 120’0;[1] by heating 2,4,6-trinitrotoluene with fuming nitric acid in a sealed tube at 180’0 for three hours;[2] by heating 2,4,6-trinitrobenzoic acid or its sodium salt with water, alcohol, dilute sodium carbonate or other suitable solvent.[3]

[1] Ber. 9, 402 (1876); Ann. 215, 344 (1882).

[2] Ber. 16, 1596 (1883).

[3] D. R. P. 77,353; Frdl. 4, 34 (1894).

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Chicago: Unknown, "XXIV 1,3,5-Trinitrobenzene," Organic Syntheses, ed. Bryant Conant, James in Organic Syntheses Original Sources, accessed January 27, 2023, http://www.originalsources.com/Document.aspx?DocID=8F243VXK7U92LFS.

MLA: Unknown. "XXIV 1,3,5-Trinitrobenzene." Organic Syntheses, edited by Bryant Conant, James, in Organic Syntheses, Original Sources. 27 Jan. 2023. http://www.originalsources.com/Document.aspx?DocID=8F243VXK7U92LFS.

Harvard: Unknown, 'XXIV 1,3,5-Trinitrobenzene' in Organic Syntheses, ed. . cited in , Organic Syntheses. Original Sources, retrieved 27 January 2023, from http://www.originalsources.com/Document.aspx?DocID=8F243VXK7U92LFS.