question_answer

Benzene on treatment with a mixture of cone. \[\text{HN}{{\text{O}}_{\text{3}}}\]and cone. \[{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\]at \[\text{100}{{\,}^{o}}\text{C}\]gives

A)  nitrobenzene

B)  m-dinitrobenzene

C)  p-dinitrobenzene

D)  o-dinitrobenzene

Correct Answer: B

Solution :

 At \[60{{\,}^{o}}C\](low temperature) mononitration occurs and nitrobenzene is obtained but at \[100{{\,}^{o}}C,\]   nitrobenzene   further   undergoes electrophilic    substitution    and    gives  m-dinitrobenzene   (as   \[-\text{N}{{\text{O}}_{\text{2}}}\]   is   a meto-directing group).