Question

Compound ‘R’ on heating with \[{\text{aq}}{\text{.NaOH}}\] evolves \[{\text{N}}{{\text{H}}_{\text{3}}}\] gas.On heating with bromine in\[{\text{aq}}{\text{.NaOH}}\] evolves \[{\text{C}}{{\text{O}}_{\text{2}}}\] gas.With \[{\text{NaN}}{{\text{O}}_{\text{2}}}{\text{/HCl}}\],it evolves \[{{\text{N}}_{\text{2}}}\] gas.Compound ‘R’ is;

A.
B.

.

C.
                   

D.
         

Answer 1

Hint: The above stated compound R will be an aromatic compound. It undergoes mainly three reactions. At first it is hydrolysed when heated with \[{\text{aq}}{\text{.NaOH}}\] . Then it undergoes Hoffmann Bromamide reaction. Finally, it is diazotized when treated with \[{\text{NaN}}{{\text{O}}_{\text{2}}}{\text{/HCl}}\]. The compound that undergoes these reactions will be surely an aromatic compound.

Complete step by step answer:
The compound when heated with \[{\text{aq}}{\text{.NaOH}}\] gives the \[{\text{N}}{{\text{H}}_{\text{3}}}\] gas which means that there is the presence of an -\[{\text{N}}{{\text{H}}_{\text{2}}}\] group.
The reaction with heating the compound with Bromine in \[{\text{aq}}{\text{.NaOH}}\] is the Hoffmann Bromamide reaction. In this reaction the amides are converted to primary amines with one carbon atom less than the parent amide. Here \[{\text{RCON}}{{\text{H}}_{\text{2}}}\] gets converted to \[{\text{RN}}{{\text{H}}_{\text{2}}}\].
And finally, when this \[{\text{RN}}{{\text{H}}_{\text{2}}}\] is treated with \[{\text{NaN}}{{\text{O}}_{\text{2}}}{\text{/HCl}}\], the diazonium salt of the corresponding compound is formed.
From these reactions we can make sure that the compound contains a- \[{\text{CON}}{{\text{H}}_{\text{2}}}\] group and it is an aromatic compound. Therefore, the compound R will be benzamide. The three reactions can be shown as below:

1.Heating with \[{\text{aq}}{\text{.NaOH}}\]

     

       Benzamide Sodium Benzoate

2.Hoffmann Bromamide Reaction
             

 Benzamide Aniline

3.Diazotisation
              

                Benzoic Acid Benzonitrile

From these reactions we are clear that the compound R is Benzamide, \[{{\text{C}}_{\text{6}}}{{\text{H}}_{\text{5}}}{\text{CON}}{{\text{H}}_{\text{2}}}\].


So, the correct answer is Option C.

Additional Information:
Amides are a group of chemicals with general formula \[{\text{RCON}}{{\text{H}}_{\text{2}}}\]. Amides are divided into subclasses according to the number of substituents on the nitrogen atom. Benzamide is an aromatic amide having a benzene ring attached to the amide group.

Note: Hoffmann Bromamide reaction is an important organic named reaction. It is used to convert amides into primary amines with one carbon atom less than the parent amide. Also, the diazotization reaction is also an important intermediate reaction in the preparation of a wide variety of organic compounds.