Why do the nitro groups change the relative leaving tendencies of the carboxy and 2,4-dinitrophenoxy groups in the tetrahedral intermediate?
Nucleophilic substitution tendencies of aromatic rings are enhanced by the electron withdrawing nitro groups, which is an important functional group in organic chemistry. Nitro group because of its electro withdrawing nature makes the adjacent C-H bonds acidic in nature.
We know that carboxylic acids are strong bases. Hence carboxylate anion which is the conjugate base of carboxylic acids will be a weak base. When there is no nitro substituents on the aromatic ring, the carboxylate ion is a weaker base( a poorer leaving group) than the 2,4-dinitrophenolate ion, so the tetrahedral intermediate reforms the anhydride but in contrast, the 2,4-dinitrophenolate ion is a weaker base( a poorer leaving group) than the carboxylate ion and hence the tetrahedral intermediate forms the ester.
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