Question

Write the preparation method of nitro-benzene. Explain any three reduction properties of nitro-Benzene with equations

Answer 1

Benzene is nitrated with a mixture of conc nitric acid and conc sulphuric acid to form nitrobenzene. Temperature is kept below 100 deg C to prevent further nitration to meta-dinitrobenzene.

$C_6{H}_6+\text{conc}HN{O}_3\stackrel{\text{conc.}{H}_{2}S{O}_{4}50{}^{o}C}{\to }{C}_6{H}_5-N{O}_2+H_{2}O$
In strong acidic medium, nitrobenzene is reduced to aniline in presence of Sn/HCl.
$C_6{H}_5-N{O}_2+6\left[H\right]\stackrel{\text{Sn + HCl}}{\to }{C}_6{H}_5-N{H}_2+2H_{2}O$
In neutral medium, nitrobenzene is rduced to nitrosobenzene in presence of Zn dust and ammonium chloride. Further reduction gives phenyl hydroxyl amine.
$C_6{H}_5-N{O}_2\stackrel{\text{Zn dust +}N{H}_{4}Cl}{\to }{C}_6{H}_5-N=O\stackrel{\text{2[H]}}{\to }{C}_6{H}_5-NH-OH$
In acidic medium, nitrobenzene is reduced to a mixture of nitrosobenzene and phenyl hydroxyl amine.
$C_6{H}_5-N{O}_2\stackrel{\text{Zn + NaOH}}{\to }{C}_6{H}_5-N=O+C_6{H}_5-NH-OH$