Given below are two statements, one is labelled as Assertion (A) and other is labelled as Reason (R).
Assertion (R) : Gabriel phthalimide synthesis cannot be used to prepare aromatic primary amines.
Reason : Aryl halides do not undergo nucleophilic substitution reaction.
In the light of the above statements, choose the correct answer from the options given below:

In the Gabriel phthalimide synthesis we first convert phthalimide into its potassium salt, represented as $$$\mathrm{C_{6}H_{4}(CO)_{2}NH + KOH \;\longrightarrow\; C_{6}H_{4}(CO)_{2}NK + H_{2}O}.$$$

This potassium phthalimide then reacts with an alkyl (or aryl) halide through a nucleophilic substitution (specifically an $$\mathrm{S_{N}2}$$ mechanism) to give an N-substituted phthalimide: $$$\mathrm{C_{6}H_{4}(CO)_{2}NK + R{-}X \;\longrightarrow\; C_{6}H_{4}(CO)_{2}N{-}R + KX}.$$$

Finally, basic or acidic hydrolysis of the N-substituted phthalimide liberates the corresponding primary amine: $$$\mathrm{C_{6}H_{4}(CO)_{2}N{-}R + 2\,H_{2}O \;\longrightarrow\; C_{6}H_{4}(COOH)_{2} + RNH_{2}.}$$$

For an aromatic primary amine we would need $$\mathrm{R = Ar},$$ i.e. the halide must be an aryl halide such as $$\mathrm{Ar{-}Cl}$$ or $$\mathrm{Ar{-}Br}.$$ Therefore the key reaction step would have to be

$$$\mathrm{C_{6}H_{4}(CO)_{2}NK + Ar{-}X \;\longrightarrow\; C_{6}H_{4}(CO)_{2}N{-}Ar + KX}.$$$

This step can occur only if the aryl halide undergoes nucleophilic substitution. However, aryl halides possess a carbon-halogen bond that is strengthened by resonance with the benzene ring, giving it partial double-bond character. They also lack the steric and electronic conditions required for the $$\mathrm{S_{N}1}$$ or $$\mathrm{S_{N}2}$$ mechanisms. Hence, aryl halides do not undergo nucleophilic substitution reactions under normal Gabriel-synthesis conditions.

Because this nucleophilic substitution does not take place, the intermediate $$\mathrm{C_{6}H_{4}(CO)_{2}N{-}Ar}$$ cannot be formed, and consequently aromatic primary amines cannot be prepared by the Gabriel method. Therefore the assertion that “Gabriel phthalimide synthesis cannot be used to prepare aromatic primary amines” is true, and the stated reason “Aryl halides do not undergo nucleophilic substitution reaction” is also true.

Moreover, the inability of aryl halides to participate in nucleophilic substitution is precisely the reason why the Gabriel synthesis fails for aromatic substrates. Thus the reason correctly explains the assertion.

Hence, the correct answer is Option 3.