Question

Nitrobenzene can be converted into azobenzene by reduction with

• A. \(Zn,\ NH_4Cl,\ \Delta\)
• B. \(Zn/NaOH,\ CH_3OH\)
• C. \(Zn/NaOH\)
• D. \(LiAlH_4,\ ether\)

Hint:

Nitrobenzene in alkaline medium with Zn undergoes coupling to form azobenzene. In acidic medium, it mainly forms aniline.

Answer 1

The Correct Option is B

Step 1: Identify reduction product based on conditions.
Nitrobenzene reduction can give different products depending on medium.
In alkaline medium, partial reduction and coupling leads to azo compounds.
Step 2: Alkaline reduction produces azobenzene.
Using \(Zn/NaOH\) in presence of alcohol (methanol), nitrobenzene reduces and couples to form:
\[ C_6H_5-N=N-C_6H_5 \] which is azobenzene.
Step 3: Why other reagents do not form azo.
\(LiAlH_4\) gives aniline.
\(Zn/NH_4Cl\) is mild acidic, gives phenylhydroxylamine/aniline.
Final Answer: \[ \boxed{Zn/NaOH,\ CH_3OH} \]