Question:

An aromatic compound $'A'$ having molecular formula ${C7H6O2}$ on treating with aqueous ammonia and heating forms compound $'B'$. The compound $'B'$ on reaction with molecular bromine and potassium hydroxide provides compound $'C'$ having molecular formula ${C_6H_7N}$. The structure of $'A'$ is :

Updated On: Oct 10, 2024
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The Correct Option is C

Solution and Explanation

First, we find the DU of each compound.
$DU \left( C _{7} H _{6} O _{2}\right)=5$
$DU \left( C _{6} H _{7} N \right)=4$
When $C _{7} H _{6} O _{2}$ reacts with aqueous ammonia and heated it forms $C _{7} H _{7} ON$.Now, $DU \left( C _{7} H _{7} ON \right)=5$
The reagent $Br _{2} / NaOH$ is classic Hoffman Bromamide reagent and this gives a clue that B may be an Amide. This consumes one DU and by seeing remaining 6 carbon and 5 Hydrogens we can say B is Benzamide.
So Benzamide on Hoffman Degradation gives Aniline which matches with the formula of $C$.
We have to know usually $NH _{3}+$ heat gives an Amide when a carboxylic acid is used as a reagent.
So among the options, we can see option C which is a Benzoic acid matches the formula of $X$ and hence is the correct answer.


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Concepts Used:

Amines

Amine is a type of compound which is derived from ammonia (NH3). According to Organic chemistry, they are basically classified as the functional groups of the organic nitrogen compounds that contain nitrogen atoms with a lone pair.

Amine - Types

Primary Amines:

It is formed when one hydrogen atom in ammonia is substituted by an alkyl or aromatic group. Amino acids and methyl amine are the best examples that why aromatic amines include aniline.

Secondary Amines:

Amines that have two organic substitutes either alkyl or aryl ones or both and are bound to the nitrogen together with one hydrogen are termed as secondary amines. For Example, Dimethylamine.

Tertiary Amines:

Tertiary Amines are the amines where the nitrogen consists of three organic substitutes. For example, Trimethylamine and EDTA.