Question

Benzene undergoes the following sequence of reactions:

Find the percentage of nitrogen in compound \( (E) \).

Hint:

For multistep organic conversions: \begin{itemize} \item Identify directing effects before predicting substitution \item Protect functional groups when required (e.g., acetylation of amines) \item Always compute percentage composition from molecular formula \end{itemize}

Answer 1

Correct Answer: 20.29

Step 1: Identify each compound in the reaction sequence: \begin{itemize} \item \( (A) \): Nitrobenzene (nitration of benzene) \item \( (B) \): Aniline (reduction of nitro group by Sn/HCl) \item \( (C) \): Acetanilide (acetylation with acetic anhydride) \item \( (D) \): \textit{p}-Nitroacetanilide (nitration, para-directing acetamido group) \item \( (E) \): \textit{p}-Nitroaniline (acidic hydrolysis) \end{itemize}
Step 2: Molecular formula of \textit{p}-nitroaniline: \[ \mathrm{C_6H_6N_2O_2} \]
Step 3: Calculate molar mass: \[ 6(12) + 6(1) + 2(14) + 2(16) = 72 + 6 + 28 + 32 = 138 \]
Step 4: Percentage of nitrogen: \[ %\text{N} = \frac{28}{138} \times 100 = 20.29% \]