Question

Among following statements on the nitration of aromatic compounds, the false one is:
A. The nitration of benzene is almost the same as that of hexadeuterobenzene.
B. The rate of nitration of toluene is greater than that of benzene.
C. The rate of benzene is greater than that of hexadeuterobenzene.
D. Nitration is an electrophilic substitution reaction.

Answer 1

Nitration is the introduction of one or more nitro groups $\left( { - {{N}}{{{O}}_2}} \right)$ into a reacting molecule. Nitro groups are replaced by hydrogen atoms. There are different nitrating agents. They are fuming, concentrated and aqueous nitric acid; mixtures of nitric acid with sulfuric acid, acetic acid, acetic anhydride, phosphoric acid and chloroform; nitrogen pentoxide and nitrogen tetroxide.

Complete step by step answer:
Nitric acid-sulfuric acid is the most important nitrating medium. Nitric acid exists in strong sulfuric acid as the nitryl ion ${{N}}{{{O}}_2}^ +$. The nitration of aromatic compounds can be represented by the equation given below:
${{ArH}} + {{HN}}{{{O}}_3} \to {{ArN}}{{{O}}_2} + {{{H}}_2}{{O}}$
Nitryl ion is an electrophilic reactant. Carbon atoms of aromatic rings contain strong electron density. Nitro group is attached to ortho, meta and para positions depending upon the electron density. According to the theory of aromatic substitution, a substituent influences the electron density in two different ways-inductive effect and mesomeric effect.
Hexadeuterobenzene is the benzene compound in which hydrogen is replaced by deuterium. The rate does not depend upon the ${{C - H}}$ or ${{C - D}}$ bond breaking. Thus the rate of nitration of both are equal.
In toluene, the methyl group is electron donating. It donates the electrons to the ring and stabilizes the intermediate form. Moreover, methyl groups are more reactive than benzene. Thus nitration of benzene is easier in toluene than in benzene.

So the false statement is option C.

Note: The mechanism of nitration involves the following three steps:
The formation of electrophile,The electrophile attacks the benzene ring,Removal of proton