The pKa of five substituted benzoic acids are given. Based on the pKa values, the corresponding substituted benzenes are to be arranged in the increasing order of their reactivity towards aromatic electrophilic substitution. Further if pKa of benzoic acid is 4.19, which substituents are activators and which are deactivators also is to be stated. Concept introduction: Electron releasing substituents present on the benzene ring in substituted benzoic acids destabilize the carboxylate anion and make the acids less acidic. Electron withdrawing substituents present on the benzene ring in substituted benzoic acids stabilize the anion and make the acids more acidic. Lower the pKa value the stronger the acid. The effects are reversed in aromatic electrophilic substitution reactions. Electron releasing substituents activate the ring towards electrophiles while the electron withdrawing substituents deactivate the ring towards electrophiles. Thus groups which are good activators reduce the acidity of the acid. To arrange: The substituted benzenes in the five carboxylic acids (pKa values given) in the increasing order of their reactivity towards aromatic electrophilic substitution. Further to state, if pKa of benzoic acid is 4.19, which substituents are activators and which are deactivators

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On what basis are Na and Nb ranked against each other?

Answer 1

Question

Chapter 20.SE, Problem 62AP

Interpretation Introduction

Interpretation:

The pKa of five substituted benzoic acids are given. Based on the pKa values, the corresponding substituted benzenes are to be arranged in the increasing order of their reactivity towards aromatic electrophilic substitution. Further if pKa of benzoic acid is 4.19, which substituents are activators and which are deactivators also is to be stated.

Concept introduction:

Electron releasing substituents present on the benzene ring in substituted benzoic acids destabilize the carboxylate anion and make the acids less acidic. Electron withdrawing substituents present on the benzene ring in substituted benzoic acids stabilize the anion and make the acids more acidic. Lower the pKa value the stronger the acid.

The effects are reversed in aromatic electrophilic substitution reactions. Electron releasing substituents activate the ring towards electrophiles while the electron withdrawing substituents deactivate the ring towards electrophiles.

Thus groups which are good activators reduce the acidity of the acid.

To arrange:

The substituted benzenes in the five carboxylic acids (pKa values given) in the increasing order of their reactivity towards aromatic electrophilic substitution. Further to state, if pKa of benzoic acid is 4.19, which substituents are activators and which are deactivators

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On what basis are Na and Nb ranked against each other?

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