Question

Under which of the following reaction conditions, aniline gives $p-$nitro derivative as the major product?

• A. Acetic anhydride/pyridine followed by conc. $H_{2}S{O}_4+conc.HN{O}_3$
• B. Acetyl chloride/pyridine followed by reaction with conc.$H_{2}S{O}_4+conc.HN{O}_3$
• C. Dil. HCl followed by reaction with conc. $H_{2}S{O}_4+conc.HN{O}_3$
• D. Reaction with conc. $HN{O}_3+conc.H_{2}S{O}_4$

Answer 1

Answer: (A), (B)

Acetyl chloride/pyridine followed by reaction with conc.$H_{2}S{O}_4+conc.HN{O}_3$

Analysing the options
Options $A$ and $B$
The $-N{H}_2$ group increases the electron density at the ortho and the para positions. So, the substitution of the incoming electrophile occurs at the ortho and the para positions.
Aniline on reaction with acetyl chloride or acetic anhydride in the presence of pyridine produces $N-$acetyl aniline. $N-$acetyl aniline is an ortho, para directing group, which on further reaction with the nitrating mixture $(conc.HNO3+conc.H2SO4)$ produces $4-$nitroacetanilide preferentially as shown below:


Options $\left(C\right)$ and $\left(D\right)$
In the case of options $\left(C\right)$ and $\left(D\right)$, aniline will react with acid and form anilinium ion, which decreases the electron density at the ortho and the para positions. So, meta products will be the major products.
So, options $\left(A\right)$ and $\left(B\right)$ are the correct answers.