Chapter 43, Problem 1Q

Interpretation Introduction

Interpretation: The reason for the formation of methyl m -nitrobenzoate instead of ortho and para isomers in the following reaction needs to be explained:

Concept Introduction: The organic reactions where an atom which is attached to an aromatic ring/system is replaced by an electrophile is said to be electrophilic aromatic substitution reaction. Generally, in this type of reaction the replacement of hydrogen atom attached to benzene ring takes place by an electrophile.

Answer to Problem 1Q

Due to the presence of an electron-withdrawing group that is ester group ( ${\text{-COOCH}}_{\text{3}}$ ) on methyl benzoate, the electron density at  ortho  and  para  position is less and incoming electrophile will attack position where the electron density is high that is at  the meta  position.

Explanation of Solution

The methyl benzoate is less reactive towards aromatic electrophilic substitution due to the presence of an electron-withdrawing group that is the ester group, ${\text{-COOCH}}_{\text{3}}$ .

Due to the -R effect (The withdrawal of electrons from one molecule by the other group in a molecule through delocalization is said to be a negative resonance effect (-R effect)), the ${\text{-COOCH}}_{\text{3}}$ group withdraws electron density from the benzene ring as:

The partial positive charge is present at  ortho  and  para  position on the benzene ring and thus, it will deactivate the benzene ring towards electrophilic substitution reactions. The incoming electrophile will attack on a position where the electron density is high that is at  the meta  position.