Read the passage carefully and answer the questions.

Amines are considered to be derivatives of ammonia obtained by replacement of hydrogen atoms with alkyl or aryl groups. They are usually prepared from nitro compounds, halides, amides, imides etc. The presence of hydrogen bonding influences its physical properties. In alkylamines, a combination of electron releasing steric and hydrogen bonding factors influences the stability of substituted ammonium cations in protic polar solvents and thus affects the basic nature of amines. Alkyl amines are found to be stronger bases than ammonia which is more basic than water. Primary and secondary amines are engaged in intermolecular association due to hydrogen bonding. This intermolecular association is more in primary amines than in secondary amines. Tertiary amines do not have intermoleulcar association due to the absence of hydrogen atom available for hydrogen bonding. Thus, the boiling point of amines depends on hydrogen bonding. In aromatic amines, electron releasing and withdrawing groups increase and decrease their basic character. Aryl diazonium salts usually obtained from arylamine undergo replacement of the diazonium group with a variety of nucleophile. Their coupling reaction of aryl diazonium salts with phenol or arylamine results in formation of dyes.

Carbylamine reaction is used as a test for

Primary aliphatic and aromatic amine

The correct answer is Option (2) → Primary aliphatic and aromatic amine

Carbylamine (isocyanide) test = Identification of primary amines only (both aliphatic and aromatic).

Explanation (Option-wise)

Option 1: Primary aliphatic amine

Primary aliphatic amines do give the carbylamine (isocyanide) test. When heated with chloroform and alcoholic $\text{KOH}$, they form foul-smelling isocyanides. However, this test is not limited only to aliphatic amines, so this option is incomplete.

Option 2: Primary aliphatic and aromatic amine

Both primary aliphatic ($\text{R--NH}_2$) and aromatic ($\text{Ar--NH}_2$) amines respond to the carbylamine test. They react with $\text{CHCl}_3$ and alcoholic $\text{KOH}$ to form isocyanides ($\text{R--NC}$), which have a very unpleasant odor. This reaction does not occur with secondary or tertiary amines, making it a specific test for primary amines.

Option 3: Secondary aliphatic amine

Secondary amines ($\text{R}_2\text{NH}$) lack the required hydrogen on nitrogen for isocyanide formation. Hence, they do not give the carbylamine test. No foul smell or isocyanide is formed.

Option 4: Secondary aromatic amine

Secondary aromatic amines (like diphenylamine) also do not have the necessary $-\text{NH}_2$ group. Therefore, they fail to produce isocyanides and do not respond to this test.