Nitration of benzoic acid

The preparation of a number of miscellaneous acids is described. m-Nitrobenzoic acid. Although m-nitrobenzoic acid is the main product of the direct nitration of benzoic acid with potassium nitrate and concentrated sulphuric acid, the complete separation of the small quantity of the attendant para isomer is a laborious process. It is preferable to nitrate methyl benzoate and hydrolyse the resulting methyl w-nitrobenzoate, which is easily obtained in a pure condition ... 

Dinitrobenzoic acid. This acid may be prepared by the nitration of benzoic acid with a mixture of concentrated sulphuric acid and fuming nitric acid under special conditions (see also Section VII,22) ... 

Some interesting results have been obtained by Akand and Wyatt56 for the effect of added non-electrolytes upon the rates of nitration of benzenesulphonic acid and benzoic acid (as benzoic acidium ion in this medium) by nitric acid in sulphuric acid. Division of the rate coefficients obtained in the presence of nonelectrolyte by the concentration of benzenesulphonic acid gave rate coefficients which were, however, dependent upon the sulphonic acid concentration e.g. k2 was 0.183 at 0.075 molal, 0.078 at 0.25 molal and 0.166 at 0.75 molal (at 25 °C). With a constant concentration of non-electrolyte (sulphonic acid +, for example, 2, 4, 6-trinitrotoluene) the rate coefficients were then independent of the initial concentration of sulphonic acid and only dependent upon the total concentration of non-electrolyte. For nitration of benzoic acid a very much smaller effect was observed nitromethane and sulphuryl chloride had a similar effect upon the rate of nitration of benzenesulphonic acid. No explanation was offered for the phenomenon. 

The nitration of benzoic acid produces only very small yields of the />-nitro product.1 The only practical method for the preparation consists in the oxidation of >-nitrotoluene,... 

Some substrates like benzoic acid, benzaldehyde etc. are so deactivated that direct nitration to their trinitro derivatives is not possible. Direct nitration of benzoic acid with excess fuming nitric and concentrated sulfuric acids at a temperature of 145 °C for several hours results in the formation of 3,5-dinitrobenzoic acid (54-58 %). The use of oleum in such reactions can significantly reduce the rate of nitration due to carbonyl protonation (see Section 4.3.3). Consequently, indirect routes are used for the synthesis of polynitroarylenes like 2,4,6-trinitrobenzoic acid and 2,4,6-trinitrobenzaldehyde (Section 4.9). 

The method is often important in the preparation of hydroxy derivatives of compounds the groups in which render them difficult to prepare by more direct means. m-Hydroxybenzoic acid is such a compound. It is obtained by nitration of benzoic acid followed by reduction to m-amino-benzoic and application of the present reaction (see below). 

Dinitrobenzoic acid has been prepared by nitration of benzoic acid with sulfuric acid and fuming nitric acid 1 by nitration of 3-nitrobenzoic acid 2 and by oxidation of 3,5-dinitrotol-uene.1, 3 It has been obtained along with other products by the action of nitric acid upon 1,5-dinitronaphthalene.4... 

S-Dinitrobenzoyl chloride. Mol. wt. 230.57, m.p. 68°. Suppliers H. H, E, The corresponding acid is prepared by nitration of benzoic acid suppliers Eastman, Light. A process of piiriHcaliun of the acid for use in the deicrminuiion of creatinine is reported.". ... 

Derivation (1) Nitration of benzoic acid (2) oxidation of o-mtrotolucnc with Mn02 and sulfuric acid, (3) oxidation of p-nitrotoluene by hot chromic acid mixture. 

Nitration of toluene yields a product with the two substituents para to each other, whereas nitration of benzoic acid yields a product with the substituents meta to each other. Again, we see that the order in which the reactions are performed is critical. 

Quite another situation is seen in the nitration of benzoic acid. First, the reaction requires the more reactive fuming nitric acid and a higher temperature than for benzene. Because nitration of benzoic acid proceeds much more slowly than nitration of benzene itself, we say that a carboxyl group is strongly deactivating. 

As another example of the importance of the order in electrophilic aromatic substitutions, consider the conversion of toluene to p-nitrobenzoic acid. The nitro group can be introduced with a nitrating mixture of nitric and sulfuric acids. The carboxyl group can be produced by oxidation of the methyl group of toluene (Section 21.5A). Nitration of toluene yields a product with the two substituents in the desired para relationship. Nitration of benzoic acid, on the other hand, yields a product with the substituents meta to each other. 

Nitration of benzoic acid. Electrophilic attack meta and para to the carboxyl group. 

Write the structure(s) of the major product(s) that you expect from each of the following electrophilic aromatic substitutions, (a) Snlfonation of methoxybenzene (anisole) (b) bromination of nitrobenzene (c) nitration of benzoic acid (d) Friedel-Crafts acetylation of chlorobenzene. 

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