The steam volatile compounds among the following are :
Choose the correct answer from the options given below:

Solution

Chemistry ma’am · 3 steps

Look for -NO₂ ortho to -OH or -NH₂: that internal H-bond lets steam carry it.

1. What steam needs. Steam distillation works for compounds that do not dissolve in water and have a good vapour pressure near 100 °C. Molecules held to each other by intermolecular H-bonds are not volatile enough.
2. Ortho H-bonding. When -NO₂ sits ortho to -OH or -NH₂, the H bonds to a nitro oxygen in the same molecule and closes a six-membered ring (chelation). The molecule is then not tied to its neighbours or to water, so it distils with steam.

   Compound	Type of H-bonding	Steam volatile?
   (A) o-nitrophenol	intramolecular, O-H … O of NO₂	yes
   (B) o-nitroaniline	intramolecular, N-H … O of NO₂	yes
   (C) p-aminophenol	intermolecular only, the groups are too far apart	no
   (D) p-aminophenol, the same as (C) drawn flipped	intermolecular only	no

3. So. Only (A) and (B) are steam volatile, which is option (c).

The idea to keep. Ortho isomers with an internal H-bond, like o-nitrophenol and o-nitroaniline, are steam volatile. Para isomers H-bond to their neighbours instead and stay behind in the flask.

Answer from the NTA final answer key. Solution by PrepWiser.