The halogen atom in haloalkanes is more electronegative than the carbon atom attached to it. As a result, the atom acquires a partial positive charge and the halogen atom a partial negative charge.

The presence of this small positive charge on the carbon atom makes it susceptible to attack by nucleophilic reagents. Thus, when a nucleophile stronger than the halide ion approaches the positively charged carbon atom of an alkylhalide, the halogen atom with its bonding pair of electrons is displaced and a new bond between the carbon atom and the incoming nucleophile is formed:

Such reactions in which a stronger nucleophile displaces a weaker nucleophile are called nucleophilic substitution reactions and the atom or group which departs with its bonding pair of electrons is called leaving group. The better the leaving group, the more facile the nucleophilic substitution reaction.

Amongst the halide ions, the order in which the leaving group departs follows the sequence:

\[I^− > Br^− > Cl^− > F^−\]

It is because of this reason that the order of reactivity of haloalkanes follows the sequence:

\[iodoalkanes > bromoalkanes > chloroalkanes > fluoroalkanes\]

There are two types of nucleophilic substitution reactions. These are:

(a)   Substitution Nucleophilic Bimolecular (S_N2)

(b)   Substitution Nucleophilic Unimolecular (S_N1)

Chlorination of toluene in the presence of light and heat followed by treatment with aqueous NaOH gives

Benzoic acid

The correct answer is option 4. Benzoic acid.

Chlorination of toluene in the presence of light and heat followed by treatment with aqueous NaOH gives Benzoic acid.