Chloroarenes (aryl chlorides) and bromoarenes (aryl bromides) can be easily prepared by direct chlorination or bromination of benzene or other aromatic hydrocarbons. These reactions are carried out in dark, at ordinary temperatures (310–320 K) in the presence of Lewis acid catalyst such as anhydrous ferric or aluminium halides (FeCl₃, FeBr₃, AlCl₃). These reactions are called electrophilic substitution of arenes. The Lewis acid acts as a catalyst and its function is to carry the halogen to the aromatic hydrocarbon and is also called halogen carrier. In actual practice, iron filings in the presence of chlorine or bromine are commonly used. The halogens react with iron filings to form corresponding Lewis acids.

What happens when toluene reacts with excess chlorine in the presence of anhydrous FeCl₃ (Major product)?

p-Chlorotoluene

The correct answer is option 3. p-Chlorotoluene.

When toluene reacts with excess chlorine in the presence of anhydrous FeCl₃, the major product is p-chlorotoluene. This is because the chlorine atoms are more likely to attack the para position of the toluene ring. The para position is the most stable position for the chlorine atoms because it is the most symmetrical.

The other products of the reaction are o-dichlorobenzene and m-chlorotoluene. However, these products are formed in smaller amounts than p-chlorotoluene.

Here is the balanced chemical equation for the reaction of toluene with excess chlorine in the presence of anhydrous FeCl₃: