Org. Synth. 1923, 3, 73
DOI: 10.15227/orgsyn.003.0073
m-NITROBENZOIC ACID
[Benzoic acid, m-nitro-]
Submitted by Oliver Kamm and J. B. Segur.
Checked by H. T. Clarke and E. R. Taylor.
1. Procedure
In a
2-l. round-bottomed flask fitted with a
reflux condenser are placed a solution of
80 g. (2 moles) of sodium hydroxide in 320 cc. of water
(Note 1) and
181 g. (1 mole) of methyl m-nitrobenzoate (not recrystallized,
p. 372). The mixture is heated to boiling during five to ten minutes or until the saponification is complete as shown by the disappearance of the ester.
The reaction mixture is now diluted with a equal volume of water, and when cool is poured, with stirring, into 250 cc. of concentrated hydrochloric acid (Note 2). After the solution has cooled to room temperature, the m-nitrobenzoic acid is filtered off by means of suction. This crude acid when dry weighs 150–160 g. (90–96 per cent of the theoretical amount). It has a light brownish color, melts at 140°, and should be completely soluble in ether, thus showing the absence of salts. This acid is satisfactory for many purposes, but in order to prepare a perfectly pure product it must be crystallized once from 1 per cent aqueous hydrochloric acid (Note 3). A light cream-colored product is thus obtained with a loss of about 5 per cent of the material (Note 4).
2. Notes
1.
The use of a more dilute
sodium hydroxide solution than that recommended above has been found to yield unsatisfactory results in the saponification of the ester. Prolonged boiling may lead to the production of colored products.
2.
After the hydrolysis of the
methyl m-nitrobenzoate it is essential that the solution of the sodium salt be poured into the acid. If acid is added to the salt in the usual way, a less soluble acid salt separates; and, as this cannot be entirely removed from the
m-nitrobenzoic acid even on long digestion with
hydrochloric acid, a product is obtained which does not dissolve completely in
ether.
3.
m-Nitrobenzoic acid is soluble to the extent of 1 part in 300 parts of water at 20°, and 20 parts at 100°. The crystallization from water or dilute
hydrochloric acid is therefore quite satisfactory.
4.
m-Nitrobenzoic acid is obtained in a higher yield by nitration of
methyl benzoate (p. 372) with subsequent hydrolysis than by the direct nitration of
benzoic acid; this method is also preferable on account of the laborious nature of the methods necessary for the separation of the meta acid from the small quantities of the para isomer formed in the latter process.
3. Discussion
m-Nitrobenzoic acid can be prepared by the nitration of
benzoic acid by means of
nitric acid,
1 a mixture of
nitric and sulfuric acids,
2 or mixtures of
nitrates and sulfuric acid;
3 all these methods lead to the production of a mixture containing principally the
m-nitrobenzoic acid with a smaller proportion of the ortho and 1–2 per cent of the para isomer. Nitration of
benzotrichloride with subsequent hydrolysis also furnishes
m-nitrobenzoic acid.
4
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
nitric and sulfuric acids
nitrates and sulfuric acid
hydrochloric acid (7647-01-0)
ether (60-29-7)
sodium hydroxide (1310-73-2)
nitric acid (7697-37-2)
Benzoic acid (65-85-0)
benzotrichloride (98-07-7)
methyl benzoate (93-58-3)
m-Nitrobenzoic acid,
Benzoic acid, m-nitro- (121-92-6)
Methyl m-nitrobenzoate (618-95-1)
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