The amino group is ortho, para directing and powerful activating substituent so that aryl amines undergo the typical electrophilic substitution reactions readily. In fact, the rate of these reactions is so great that in certain cases poly-substitution, rather than mono-substitution occurs, even under mild conditions. If the reactions in such cases have have to be arrested at the mono-substitution stage, the activating influence of the –NH₂ group has to be arrested.

Identify the major product of the given reaction. 

p-Nitroaniline

The correct answer is option 3. p-Nitroaniline.

When aniline \((C_6H_5NH_2)\) reacts with a mixture of nitric acid \((HNO_3)\) and sulfuric acid \((H_2SO_4)\) at low temperature, nitration occurs. However, direct nitration of aniline using this mixture can be problematic because the amino group (NH₂) is highly reactive and can lead to over-nitration or even decomposition under strong acidic conditions. To achieve controlled nitration, typically, aniline is first converted to its acyl derivative to protect the amino group.

But for the sake of understanding the reaction directly under the conditions specified (\(HNO_3\) and \(H_2SO_4\) at low temperature), the amino group is an activating group and directs the incoming nitro group to the ortho and para positions. In practice, under these mild conditions, the para position is more sterically accessible and is often the major product.

The major product is p-Nitroaniline ( or, 4-nitroaniline). The reaction can be summarized as:

This product forms due to the para position being more accessible compared to the ortho positions, which are sterically hindered by the amino group.