Although chlorine is an electron withdrawing group, yet it is ortho- and para- directing in electrophilic aromatic substitution reaction because

(A) Chlorine withdraws electron through inductive effect

(B) Chlorine destabilizes the intermediate carbocation formed during electrophilic substitution

(C) Chlorine accepts electrons through resonance

(D) Chlorine releases electrons through resonance

Choose the correct answers from the options given below:

(A), (B) and (D) only

The correct answer is option 1. (A), (B) and (D) only.

Chlorine is indeed an electron-withdrawing group, yet it is ortho- and para-directing in electrophilic aromatic substitution reactions, typically due to resonance effects. Let us analyze each option:

(A) Chlorine withdraws electrons through inductive effect

Chlorine is more electronegative than carbon. When it is attached to a benzene ring, it pulls electron density away from the ring through the sigma bonds (inductive effect). This withdrawal of electron density makes the ortho and para positions on the benzene ring relatively electron-deficient compared to the meta position.

The electron-deficient nature of the ortho and para positions increases their reactivity towards electrophilic attack because they are better able to stabilize positive charge in the transition state of the reaction.

(B) Chlorine destabilizes the intermediate carbocation formed during electrophilic substitution

During electrophilic aromatic substitution, an electrophile attacks the aromatic ring, leading to the formation of a carbocation intermediate. Chlorine, being an electron-withdrawing group, destabilizes this intermediate carbocation. This destabilization is particularly pronounced for the meta position because it is adjacent to the electron-withdrawing chlorine atom.

The destabilization of the carbocation intermediate at the meta position makes it less favored compared to the ortho and para positions, where the destabilizing effect of chlorine is less significant.

(C) Chlorine accepts electrons through resonance

This statement is incorrect. Chlorine does not typically accept electrons through resonance. Instead, it withdraws electron density through its electronegativity.

(D) Chlorine releases electrons through resonance

Chlorine can participate in resonance with the benzene ring. In resonance, the lone pairs of electrons on the chlorine atom can delocalize onto the benzene ring, particularly towards the ortho and para positions. This delocalization of electron density onto the ortho and para positions makes them more electron-rich.

The increased electron density at the ortho and para positions enhances their reactivity towards electrophilic attack because they can better stabilize positive charge in the transition state of the reaction.

Overall Significance:

Chlorine's electron-withdrawing nature through the inductive effect makes the ortho and para positions relatively electron-deficient, enhancing their reactivity towards electrophilic attack.

Destabilization of the intermediate carbocation at the meta position makes it less favored compared to the ortho and para positions.

Participation in resonance, where chlorine releases electron density onto the ortho and para positions, further enhances their reactivity towards electrophilic attack.

Each of these factors contributes to chlorine's ortho- and para-directing nature in electrophilic aromatic substitution reactions. By withdrawing electron density through the inductive effect, destabilizing the intermediate carbocation, and releasing electron density through resonance, chlorine effectively directs incoming electrophiles to the ortho and para positions on the aromatic ring.

Therefore, the correct combination of reasons explaining why chlorine is ortho- and para-directing in electrophilic aromatic substitution reactions is option 1. (A), (B), and (D) only

These factors collectively illustrate the ortho- and para-directing behavior of chlorine in electrophilic aromatic substitution reactions.