Why chlorine in chlorobenzene is less reactive towards nucleophilic substitution than that in benzyl chloride?

Which is more reactive chlorobenzene and chloroethane in the nucleophilic substitution and why?

Open in App

CBSE 12-science - Chemistry

find the major product

Asked by mayamishra9540500880 | 04 Jul, 2022, 07:11: PM

CBSE 12-science - Chemistry

aadr

Asked by ap650712 | 26 Jun, 2021, 10:00: AM

ANSWERED BY EXPERT

Get the answer to your homework problem.

Try Numerade free for 7 days

Jillian H.

Organic Chemistry

9 months, 2 weeks ago

We don’t have your requested question, but here is a suggested video that might help.

Chlorobenzene is less reactive than benzyl chloride towards nucleophilic substitution because (a) the carbon of $\mathrm{C}-\mathrm{Cl}$ bond in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{Cl}$ is sp $^{2}$ hybridized and holds the electron pair more firmly as compared to sp $^{3}$ carbon containing chlorine in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{Cl}$. (b) the $\mathrm{C}-\mathrm{Cl}$ bond in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{Cl}$ is less polar compared to that in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{CH}_{2} \mathrm{Cl}$. (c) the C-Cl bond in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{Cl}$ acquires partial double bond character due to resonance involving the lone pair on chlorine atom. (d) the chlorine in $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{Cl}$ is deactivating due to its high electronegativity.

Text Solution

Solution : In the molecules of benzyl chloride, the electron pairs on the chlorine atom are not in a position to conjugate with the `pi`-electrons of the ring. <br> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/MBD_EM_CHE_XII_C10_E03_029_S01.png" width="80%"> <br> Whereas electron pairs on the chlorine atom are in conjugation with the `pi`-electrons of the ring in the molecules of chlorobenzene. Consequently, the C-Cl bond in chlorobenzene acquires some double bond character, which is not present in benzyl chloride. As a result, the reactivity of benzyl chloride is more than the chlorobenzene.