Chemistry · Chemical Bonding · NEET
Intermolecular means the H-bond forms between two different molecules (like water-water, or HF-HF). Many molecules link into a chain or network. Intramolecular means the H-bond forms inside a single molecule, between two groups sitting close together on the same molecule. Simple rule: inter = between molecules, intra = within one molecule. This is a common NEET one-mark trap, so read the word ending carefully.
In o-nitrophenol (ortho), the -OH group and the -NO2 group are on neighbouring carbons, so they are physically close. The -OH hydrogen can reach the oxygen of the nearby -NO2 and form a 6-membered ring inside the same molecule. This is intramolecular. In p-nitrophenol (para), the -OH and -NO2 are on opposite sides of the ring, too far apart to reach each other, so the H-bond forms between different molecules instead (intermolecular).
In o-nitrophenol the hydrogen is locked inside its own molecule, so molecules do not stick strongly to their neighbours. Weak attraction between molecules means it boils and evaporates easily (more volatile). In p-nitrophenol the H-bond joins different molecules, so the molecules cling together. You need more energy to separate them, so it has a higher boiling point and is less volatile. This is why NEET says intramolecular H-bonding lowers boiling point.
By steam distillation. o-Nitrophenol has intramolecular H-bonding, so it is steam-volatile and comes over with the steam. p-Nitrophenol has intermolecular H-bonding, so it stays behind. This exact idea was asked in NEET 2017 and the answer is steam distillation.
Yes. You need the two groups (one with H like -OH, one electronegative like -NO2 oxygen) to be close enough to form a ring. Only the ortho position places them next to each other. Meta and para positions are too far, so those isomers form intermolecular H-bonds. So among ortho, meta and para, only ortho gives intramolecular H-bonding.
Weaker. Any hydrogen bond, whether intermolecular or intramolecular, is much weaker than a normal covalent bond. It is only a partial-charge attraction (delta-plus H pulled to delta-minus O, N or F). NCERT clearly states the hydrogen bond is weaker than the covalent bond. It is still important because it changes boiling point, volatility and solubility.
The most suitable method of separation of a 1:1 mixture of ortho- and para-nitrophenols is:
Intramolecular hydrogen bonding is present in which of the following compounds? (Options A, B and D are p-, m- and o-nitrophenol; option C is HF.)
Carboxylic acids have higher boiling points than aldehydes, ketones and even alcohols of comparable molecular mass. This is due to their:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Ortho (o-nitrophenol) is more volatile because its intramolecular H-bond keeps the H inside its own molecule, so molecules do not stick together strongly.
It lowers the boiling point. The molecule uses its H internally, so there is less attraction between molecules, making it easier to boil.
Yes, if it has extra H-donor or acceptor groups left over. But when a group is already tied up in an intramolecular bond, it cannot also bond to another molecule with that same group.
Only in the ortho position are the two groups on neighbouring carbons, close enough to form a ring. Meta and para positions are too far apart.
No. It is much weaker than a covalent bond. It is only a partial-charge attraction, but it still strongly affects boiling point, volatility and solubility.
