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Question: Which sequence of steps will be able to produce 3,3'-dinitrobiphenyl from benzene?...

Which sequence of steps will be able to produce 3,3'-dinitrobiphenyl from benzene?

A

HNO3/H2SO4, Cl2/FeCl3, Na/ether

B

Cl2/FeCl3, HNO3/H2SO4, Na/ether

C

Cl2/FeCl3, H2SO4, Na/ether

D

I2/HIO3, Cl2/FeCl3, C6H5NO2

Answer

HNO3/H2SO4, Cl2/FeCl3, Na/ether

Explanation

Solution

To synthesize 3,3'-dinitrobiphenyl from benzene, a specific sequence of reactions is required to correctly place the nitro groups meta to the future C-C bond of the biphenyl.

  1. Nitration of benzene: Benzene is first nitrated using a nitrating mixture (HNO₃/H₂SO₄) to form nitrobenzene.

  2. Meta-chlorination: The nitro group (-NO₂) is a strong meta-director. Therefore, subsequent chlorination of nitrobenzene with Cl₂/FeCl₃ will yield 3-chloronitrobenzene (meta-chloronitrobenzene).

  3. Wurtz-type coupling: Two molecules of 3-chloronitrobenzene are then coupled using sodium metal in ether. This reaction removes the chlorine atoms and forms a C-C bond between the two phenyl rings at the positions previously occupied by chlorine, resulting in 3,3'-dinitrobiphenyl.