Question

Aryl halides are less reactive towards nucleophilic substitution reaction as compared to alkyl halides due to:
A. formation of a less stable carbonium ion in aryl halide
B. resonance stabilization in aryl halide
C. Presence of double bond in aryl halide
D. inductive effect in aryl halide

Answer 1

Hint: Aryl halides are less reactive towards nucleophilic substitution reaction as compared to alkyl halides is because of resonance stabilization in aryl halide. Due to resonance, C−Cl bond becomes shorter and stronger and cannot be easily replaced by nucleophiles.

Complete answer:
In this question, we have asked why aryl halide is less reactive towards nucleophilic substitution reactions while alkyl halide is more reactive. So, first of all, what are aryl and alkyl halides? An aryl halide is an aromatic compound in which one or more hydrogen atoms of an aromatic ring are replaced by a halide and alkyl halide means one or more hydrogen atoms of an alkane are replaced by halogen atoms and nucleophilic substitution reaction is a reaction in which a leaving group (nucleophile) is replaced by an electron-rich compound (electrophile). The alkyl halides are less reactive towards nucleophilic substitution reaction because of 1. More steric hindrance as compared to an alkyl halide, 2. The less negative charge on alkyl halide due to resonance in aryl halide and alkyl halide only have induction effect and we know that resonance effect>>> induction effect. We only have one reason in the option that is resonance stabilization in aryl halide.

So, the correct option will be B. resonance stabilization in aryl halide

Note: Inductive effect: The inductive effect is an effect regarding the transmission of unequal sharing of the bonding electron through a chain of atoms in a molecule, leading to a permanent dipole in a bond.
Resonance effect: Resonance effect is the conjugation between the ring and the substituent, which means the delocalizing of the π electrons between the ring and the substituent.