Haloarenes undergo the usual electrophilic reactions of the benzene ring such as halogenation, nitration, sulphonation and Friedel-Crafts reactions. Halogen atom besides being slightly deactivating is o, p-directing; therefore, further substitution occurs at ortho- and para-positions with respect to the halogen atom. The o, p-directing influence of halogen atom can be easily understood if we consider the resonating structures of halobenzene as shown:

Due to resonance, the electron density increases more at ortho- and para-positions than at meta-positions. Further, the halogen atom because of its –I effect has some tendency to withdraw electrons from the benzene ring. As a result, the ring gets somewhat deactivated as compared to benzene and hence the electrophilic substitution reactions in haloarenes occur slowly and require more drastic conditions as compared to those in benzene

Predict the minor product when chlorobenzene reacts with acteyl chloride in the presence of anhydrous AlCl₃. 

2-Chloroacetophenone 

The correct answer is option 2. 2-Chloroacetophenone.

The reaction of chlorobenzene with acetyl chloride in presence of \(AlCl_3\) is a Friedel – Crafts acylation reaction.

Friedel-Crafts acylation is a reaction in which the addition of an acyl group to an aromatic ring takes place. The reaction will lead to the aromatic ring being transformed into a ketone. Our reactant chlorobenzene. The \(Cl\) atom in Chlorobenzene is an ortho-para directing group. This is because \(Cl\) has a lone pair. Therefore, in the resonating structures of chlorobenzene, the electrons will be delocalized into the ring and the electron density on ortho and para position will be increased. The electron density will be more at ortho and para positions as there are resonating structures in which the negative charge is on the ortho para positions.

Hence, the Friedel – Crafts acylation of chlorobenzene will yield us both ortho and para products.

Therefore, the reaction of chlorobenzene with acetyl chloride in presence of \(AlCl_3\), will yield the products - 2-Chloro Acetophenone and 4-Chloro Acetophenone.

Out of the 2 products, 4-Chloro acetophenone will be the major product and 2-Chloro Acetophenone is the minor product.