Org. Synth. 1923, 3, 71
DOI: 10.15227/orgsyn.003.0071
METHYL m-NITROBENZOATE
[Benzoic acid, m-nitro-, methyl ester]
Submitted by Oliver Kamm and J. B. Segur.
Checked by H. T. Clarke and E. R. Taylor.
1. Procedure
Into a 2-l. round-bottomed flask fitted with a mechanical stirrer are placed 400 cc. of concentrated sulfuric acid cooled to 0° and 204 g. (1.5 moles) of pure methyl benzoate (Note 1). The mixture is cooled by means of an ice bath to 0–10° and then, with stirring, there is added gradually, by means of a dropping funnel, a mixture of 125 cc. (1.96 moles) of concentrated nitric acid (sp. gr. 1.42) and 125 cc. of concentrated sulfuric acid. During the addition of the nitrating acid, which requires about one hour, the temperature of the reaction mixture should be kept within the range 5–15° (Note 2).
After the nitric acid has been added, stirring is continued for fifteen minutes longer; the mixture is then poured upon 1300 g. of cracked ice. The crude methyl m-nitrobenzoate separates as a solid and is filtered off by means of suction and washed with water. The product is placed in a flask and agitated with 200 cc. of ice-cold methyl alcohol in order to remove a small amount of o-nitrobenzoic ester and other impurities that are present. The cooled mixture is then filtered by means of suction, washed with another 100-cc. portion of cold methyl alcohol (Note 3), and the solid dried. The yield is 220–230 g. (81–85 per cent of the theoretical amount) (Note 4) of an almost colorless product melting at 74–76°. In order to obtain a product of maximum purity, which melts at 78°, it is advisable to recrystallize the ester from an equal weight of methyl alcohol.
2. Notes
1.
It is necessary that the
methyl benzoate should be of high purity and dissolve in
sulfuric acid without color. Commercial
methyl benzoate which does not meet the latter specification may give yields about
10 per cent lower. Directions for the preparation of
methyl benzoate are given in Org. Syn.
10, 51, Note 13.
2.
The nitration of
methyl benzoate runs unusually smoothly, but it is essential to keep the temperature within the specified limits, otherwise the yield falls; at 50°,
193 g. of solid product is obtained, while at 70° the yield falls to
130 g.3.
On diluting the methyl alcoholic filtrate with water, 10–20 cc. of oil separates; more of this oil is formed by nitrating at higher temperatures, amounting to 57 cc. at 50° and 100 cc. at 70°. The oil consists not merely of
methyl o-nitrobenzoate with some of the meta compound but contains also traces of dinitrobenzoic ester and nitrophenolic compounds. Unchanged
methyl benzoate does not appear to be present.
4.
The nitration method is also adaptable to the preparation of
ethyl m-nitrobenzoate. The yield is, however, slightly lower, owing to the greater solubility of the ethyl ester.
3. Discussion
Methyl m-nitrobenzoate can be prepared by the esterification of
m-nitrobenzoic acid;
1 this method is, however, obviously much less satisfactory than nitration of
methyl benzoate. Nitration by means of fuming
nitric acid can also be applied to
methyl benzoate,
2 but the use of the ordinary nitration mixture of concentrated
sulfuric acid and concentrated
nitric acid is more satisfactory. Treatment of
ω-trichloro-m-nitroacetophenone with
methyl alcohol and
sodium methoxide also furnishes
methyl m-nitrobenzoate.
3
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
sulfuric acid (7664-93-9)
methyl alcohol (67-56-1)
nitric acid (7697-37-2)
sodium methoxide (124-41-4)
methyl benzoate (93-58-3)
m-Nitrobenzoic acid (121-92-6)
Methyl m-nitrobenzoate,
Benzoic acid, m-nitro-, methyl ester (618-95-1)
methyl o-nitrobenzoate (606-27-9)
Ethyl m-nitrobenzoate (618-98-4)
ω-trichloro-m-nitroacetophenone
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