Question

How can you obtain the following from aniline? Give only chemical equations.

Hint:

For nitration, use a mixture of concentrated HNO\textsubscript{3} and H\textsubscript{2}SO\textsubscript{4}, for chlorination, FeCl\textsubscript{3} is a good catalyst, and for oxidation, K\textsubscript{2}Cr\textsubscript{2}O\textsubscript{7} is used.

Answer 1

(a) Synthesis of p-Nitroaniline

Reaction: Aniline undergoes nitration using concentrated nitric acid and sulfuric acid.

\[ {C6H5NH2 + HNO3} \xrightarrow{{H2SO4}} {p-C6H4(NO2)NH2} \]

Explanation: The activating –NH\(_2\) group on aniline directs nitration to the para position, making para-nitroaniline the predominant product when reacted with a nitrating mixture.

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(b) Synthesis of Chlorobenzene

Reaction: Aniline is chlorinated in the presence of ferric chloride, a Lewis acid catalyst.

\[ {C6H5NH2 + Cl2} \xrightarrow{{FeCl3}} {C6H4ClNH2} \]

Explanation: Chlorine substitutes onto the aniline molecule. The reaction conditions are typically controlled to favor the formation of the mono-chlorinated product, chlorobenzene.

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(c) Synthesis of Phenol

Reaction: Aniline is oxidized by potassium dichromate in an acidic environment.

\[ {C6H5NH2 + K2Cr2O7 + H2SO4} \rightarrow {C6H5OH} \]

Explanation: The –NH\(_2\) group of aniline is converted to a hydroxyl group, resulting in the formation of phenol.