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 – NO 2 , p -O 2 N – C 6 H 4 – NO 2 .

Question

Philoid · Accepted Answer

We know that electrophiles are the reagents or species that participate in a reaction by accepting an electron pair in order to bond with nucleophiles.

Also, the higher the electron density of a benzene ring, the more reactive is the compound towards an electrophile, E⁺ (Electrophilic reaction).

(a) The presence of an electron withdrawing group like NO₂^- and Cl^- deactivates the aromatic ring by decreasing the electron density.

Since NO₂^- group is more electron withdrawing (due to resonance effect) than the Cl^- group (due to inductive effect), the decreasing order of the reactivity is as follows:-

Chlorobenzene > p – nitrochlorobenzene > 2, 4 – dinitrochlorobenzene

(b) We know that CH₃^- is an electron donating group and NO₂^{- the} group is electron withdrawing.

Hence, toluene will have the maximum electron density and is most easily attacked by E⁺.

NO₂^- is an electron withdrawing group. Hence, when the number of NO₂^- substituents is greater, the decreasing order of the reactivity order is as follows:

Toluene > p-H₃C – C₆H₄ – NO₂> p-O₂N – C₆H₄ – NO₂

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-H3C – C6H4 – NO2, p-O2N – C6H4 – NO2.

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-H₃C – C₆H₄ – NO₂, p-O₂N – C₆H₄ – NO₂.