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Methyl benzoate is formed by the condensation of methanol and benzoic acid, in presence of a strong acid. [1] [2] Methyl benzoate reacts at both the ring and the ester, depending on the substrate. Electrophiles attack the ring, illustrated by acid-catalysed nitration with nitric acid to give methyl 3-nitrobenzoate.
The phrase ipso nitration was first used by Perrin and Skinner in 1971, in an investigation into chloroanisole nitration. [18] In one protocol, 4-chloro- n -butylbenzene is reacted with sodium nitrite in t -butanol in the presence of 0.5 mol% Pd 2 (dba) 3 , a biarylphosphine ligand and a phase-transfer catalyst to provide 4-nitro- n -butylbenzene.
Since carboxylic acid functional groups are electron withdrawing, during an electrophilic aromatic substitution reaction of nitration, substituents are directed to a meta position which explains this regiochemistry. A less efficient route involves nitration of methyl benzoate, followed by hydrolysis. [3]
It also can be prepared by treating benzaldehyde under nitration conditions, a process that initially converts the aldehyde to the acid. 4-Nitrobenzoic acid is a precursor to 4-aminobenzoic acid , which is in turn used to prepare the anesthetic procaine . 4-Nitrobenzoic acid is prepared by oxidation of 4-nitrotoluene .
The nitration product produced on the largest scale, by far, is nitrobenzene. Many explosives are produced by nitration including trinitrophenol (picric acid), trinitrotoluene (TNT), and trinitroresorcinol (styphnic acid). [3] Another but more specialized method for making aryl–NO 2 group starts from halogenated phenols, is the Zinke nitration.
3-Nitrobenzaldehyde is the primary product obtained via the mono-nitration of benzaldehyde with nitric acid. [3] C 6 H 5 CHO + HNO 3 → O 2 NC 6 H 4 CHO + H 2 O. Product distribution is about 19% for the ortho-, 72% for the meta- and 9% for the para isomers.
In contrast, 2-methyl-1,4-dinitrobenzene (2c) is isolated in only 9.9% yield. [4] As witnessed in the above example, when a π-acceptor substituent (πAS) is meta to a π-donor substituent (πDS), the electrophilic aromatic nitration occurs ortho to the πAS rather than para. Nitration of 3-Methylbenzoic acid
A newer method uses methyl iodide and silver nitrate: [4] CH 3 I + AgNO 3 → CH 3 NO 3 + AgI. Methyl nitrate can be produced on a laboratory or industrial scale either through the distillation of a mixture of methanol and nitric acid, or by the nitration of methanol by a mixture of sulfuric and nitric acids.