Question

Which of the following is detected by carbylamine test?
A.$CO{N}_2{H}_4$
B.$C_6{H}_{5}N{H}_2$
C.$C{H}_{3}CON{H}_2$
D.$C_2{H}_{5}CN$

Answer 1

Hint: Carbylamine test: This test is given by primary amines only. This test is not given by secondary and tertiary amines, amide or urea.
In carbylamine test aliphatic or aromatic primary amines are heated with chloroform in presence of alcoholic potassium hydroxide to give foul smell isocyanide or carbylamines.

Complete step by step solution:
First of all we will talk about $1^{\circ },2^{\circ },3^{\circ }$amines and how to distinguish between these.
Amines are classified into different categories based on the position of the $-N{H}_2$ present in the group.
$1^{\circ }$amines: are also known as primary amines. In this type of amines $-N{H}_2$ group is present to only one single alkyl group. For example: ethanamine, methanamine, propanamine.
$2^{\circ }$amines: are also known as secondary amines. In this type of amines $-N{H}_2$ group is present to two alkyl groups. For example: propan$-2-$amine, butan$-2-$amine.
$3^{\circ }$amines: are also known as tertiary amines. In this type of amines $-N{H}_2$ group is present to three alkyl groups. For example: $2$-methylpropan$-2-$amine.
Carbylamine test: This test is given by primary amines only. This test is not given by secondary and tertiary amines, amide or urea.
In carbylamine test aliphatic or aromatic primary amines are heated with chloroform in presence of alcoholic potassium hydroxide to give foul smell isocyanide or carbylamines.
Here we are given with the compounds i.e. $CO{N}_2{H}_4$ which is the formula of urea which does not give a carbylamine test. In option b we are given with $C_6{H}_{5}N{H}_2$ which is the formula of benzylamine here this molecule is primary amine so it will give a carbylamine test. In option c we are given with $C{H}_{3}CON{H}_2$ which is the formula of methanamide (amide) so it will also not give a carbylamine test. And in option d we are given with $C_2{H}_{5}CN$ which is ethane cyanide which does not give carbylamine test.

Hence, option B is correct.

Note: Functional group: In the hydrogen the atoms or groups which are other than carbon and hydrogen, are known as function groups. For example: chloride if chlorine is present in the compound. And if hydroxide group i.e. $-OH$ is present then the name will be alcohol.