JEE Chemistry 2025 Question with Solution

Given: Four aromatic compounds $\text{(A)}$, $\text{(B)}$, $\text{(C)}$, and $\text{(D)}$ are given.

Find: Which compounds are steam volatile.

Steam volatile compounds are generally low-boiling compounds that can vaporize and mix with steam at low temperatures.

The deciding factor here is the type of hydrogen bonding present.

• Compounds showing intramolecular hydrogen bonding are less associated and therefore more volatile.
• Compounds showing intermolecular hydrogen bonding are more strongly associated and therefore less volatile.

From the given structures:

• $\text{(A)}$ and $\text{(B)}$ have ortho substitution that allows intramolecular hydrogen bonding.
• $\text{(C)}$ and $\text{(D)}$ have para substitution, so they mainly show intermolecular hydrogen bonding.

Therefore, the steam volatile compounds are $\text{(A)}$ and $\text{(B)}$ only.

The correct option is A.

Given: Steam distillation is possible for compounds that are volatile in steam and sufficiently less associated.

Find: Which of the given compounds are steam volatile.

Step 1: Understand the concept of steam volatility.

Steam distillation is used to separate or purify organic compounds that are volatile in steam and immiscible with water. Compounds that can undergo steam distillation are those which:

• are immiscible with water,
• have sufficient vapor pressure at the boiling point of water, that is $373 \, \text{K}$.

Step 2: Analyze the given compounds.

• $\text{(A)}$ o-Nitrophenol: due to intramolecular hydrogen bonding, it is less polar and more volatile; hence, it is steam volatile.
• $\text{(B)}$ o-Nitroaniline: it also has intramolecular hydrogen bonding, making it less associated and more volatile; hence, it is steam volatile.
• $\text{(C)}$ p-Aminophenol: it has intermolecular hydrogen bonding, which increases its boiling point, making it non-volatile in steam.
• $\text{(D)}$ p-Aminophenol: it also has intermolecular hydrogen bonding and hence is not steam volatile.

Step 3: Conclude.

Compounds $\text{(A)}$ and $\text{(B)}$ exhibit intramolecular hydrogen bonding, which lowers their effective intermolecular attraction and makes them volatile with steam. Compounds $\text{(C)}$ and $\text{(D)}$ exhibit intermolecular hydrogen bonding, leading to higher boiling points and non-volatility.

Therefore, the correct option is A.