Account for the following : (a) Aromatic carboxylic acids do not undergo Friedel-Crafts reaction. (b) `pK_(a)` value of 4-nitrobenzoic acid is lower than that of benzoic acid .

Account for the following : (a) Aromatic carboxylic acids do not under

1.	Account for the following : (a) Aromatic carboxylic acids do not undergo Friedel-Crafts reaction. (b) `pK_(a)` value of 4-nitrobenzoic acid is lower than that of benzoic acid .
Answer» (a) Aromatic carboxylic acids do not undergo Friedal-Crafts reaction because the carboxylic group is strongly deactivating and the catalyst `AlCl_(3)` (lewis acid ) gets bonded to the carboxylic group strongly . (b) Lower the value `pK_(a)` - greater will be the acidic character , 4-nitrobenzoic acid is stronger base than that of benzoic acid . Nitro group is electron withdrawing group . It has powerful electron-withdrawing resonance effects as well as electron-withdrawing inductive effect due to that it is easy to release the hydrogen . Hence , to make 4-nitrobenzoic acid stronger base.

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Account for the following : (a) Aromatic carboxylic acids do not undergo Friedel-Crafts reaction. (b) `pK_(a)` value of 4-nitrobenzoic acid is lower than that of benzoic acid .

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