Ncert Exercises & Solutions

Question 13.22:-

Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile, $E^{+}$

(a)Chlorobenzene, 2,4-dinitrochlorobenzene, p-nitrochlorobenzene
(b)Toluene, $p - H_{3} C - C_{6} H_{4} - N O_{2}, p - O_{2} N - C_{6} H_{4} - N O_{2} .$

Electrophiles are reagents that participate in a reaction by accepting an electron pair in order to bond to nucleophiles.
The higher the electron density on a benzene ring, the more reactive is the compound towards an electrophile,

$E^{+}$ (Electrophilic reaction)

(a) The presence of an electron-withdrawing group (i.e.,

${NO}_{2}^{-}$ and

${Cl}^{-}$ ) deactivates the aromatic ring by decreasing the electron density.
Since

${NO}_{2}^{-}$ the group is more electron-withdrawing (due to resonance effect) than the

${Cl}^{-}$ group (due to inductive effect), the decreasing order of reactivity is as follows: Chlorobenzene > p – nitro chlorobenzene > 2, 4 – dinitrochlorobenzene

(b) While

${CH}_{3}^{-}$ is an electron-donating group,

${NO}_{2}^{-}$ group is electron-withdrawing. Hence, toluene will have the maximum electron density and is most easily attacked by

$E^{+}$ .

${NO}_{2}^{-}$ is an electron-withdrawing group. Hence, when the number of

${NO}_{2}^{-}$ substituents is
greater, the order is as follows:

Toluene.

$> p - C H_{3} - C_{6} H_{4} - N O_{2,} p - O_{2} N - C_{6} H_{4} - N O_{2}$

NEET Information

courses

Company

Botany Questions

Chemistry Questions

Physics Questions

Zoology Questions