Question

Nitrobenzene gives azobenzene and hydrazobenzene when reduced:
(A) In acidic medium
(B) In neutral medium
(C) Electrolytic
(D) In alkaline medium

Answer 1

Nitrobenzene is an organic compound. It is a yellow oily liquid prepared by nitrating benzene. It is a water insoluble compound. The nitration process involves formation of the nitronium ion $\left( {NO_2^ + } \right)$ , followed by an electrophilic substitution reaction of it with benzene. The nitronium ion is generated by the reaction of nitric acid and sulphuric acid. The chemical formula of nitrobenzene is ${C_6}{H_5}N{O_2}$
The chemical reaction is as follows:
${C_6}{H_6}\xrightarrow[{{H_2}S{O_4}}]{{HN{O_3}}}{C_6}{H_5}N{O_2} + {H_2}O$

Complete answer:
The reduction of nitrobenzene yields amines. The amines can be primary, secondary or tertiary.
The general reduction reaction of nitrobenzene is as follows:
${C_6}{H_5}N{O_2}\xrightarrow[{ethanol}]{{{H_2},Pd}}{C_6}{H_5}N{H_2}$
The bulky benzene with nitro group yields a compound with two benzene rings.
When nitrobenzene is treated with arsenic trioxide $\left( {A{s_2}{O_3}} \right)$ or glucose $\left( {{C_6}{H_{12}}{O_6}} \right)$ and sodium hydroxide $\left( {NaOH} \right)$ then, azoxybenzene(1,2-diphenyl diamine oxidase) is formed. This is because the glucose acts as a reducing agent and removes the oxygen atom from the nitro group and produces an amine group by bonding both the nitrogen.
The reaction is as follows:
$2{C_6}{H_5}N{O_2} + 6H\xrightarrow[{NaOH}]{{A{s_2}{O_3}orglu\cos e}}{C_6}{H_5} - N = \mathop {{N_ \oplus }}\limits^{\mathop \uparrow \limits^{{O^ - }} } - {C_6}{H_5} + 3{H_2}O$
Nitrobenzene Azoxybenzene
When nitrobenzene is treated with zinc and sodium hydroxide $\left( {NaOH} \right)$ then, hydrazobenzene(1,2-diphenyl diamine) is formed. Zinc dust acts as a catalyst and increases the rate of the reduction reaction.
The reaction is as follows:
$2{C_6}{H_5}N{O_2} + 10H\xrightarrow{{Zn,NaOH}}{C_6}{H_5} - NH - NH - {C_6}{H_5} + 4{H_2}O$
Nitrobenzene Hydrazobenzene
Hence both the reduction products are derived by using sodium hydroxide that is in alkaline medium.
So, the correct answer is option (D).

Note:
When nitrobenzene is treated with methanolic solution of zinc and sodium hydroxide then, azobenzene is formed, this happens because alcohol removes the hydrogen present in amine and converts to simple nitrogen resulting in the azobenzene. The reaction is,
$2{C_6}{H_5}N{O_2}\xrightarrow[{C{H_3}OH}]{{Zn,NaOH}}{C_6}{H_5} - N = N - {C_6}{H_5}$
Nitrobenzene azobenzene