Explain a clear difference between intramolecular hydrogen bonding and intermolecular hydrogen bonding.with clear explaination and justification of examples of o-nitrophenol and p-nitrophenol .
How do we find which compound has a higher boiling point?

Asked by Ginni2k | 4th Nov, 2016, 12:23: PM

Expert Answer:

Intermolecular Hydrogen Bonding:
This occurs when the hydrogen bonding is between H-atom of one molecule and an atom of the electronegative element of another molecule.
For example
(i) hydrogen bond between the molecules of hydrogen fluoride.
(ii) hydrogen bond in alcohol or water molecules.
Intermolecular hydrogen bond results into association of molecules. Hence, it usually increases the melting point, boiling point, viscosity, surface tension, solubility, etc.  
Intramolecular Hydrogen Bonding:
This bond is formed between the hydrogen atom and an atom of the electronegative element (F,O,N) , of the same molecule .
Intramolecular hydrogen bond results in the cyclization of the molecules and prevents their association.
Consequently, the effect of this bond on the physical properties is negligible. Hence, boiling point of such compounds dose not get affected or remain low.
For example, intramolecular hydrogen bonds are present in molecules such as o-nitrophenol, o-nitrobenzoic acid, etc.
Image result for hydrogen bonding in para nitrophenol
Hence, the boiling point of o nitrophenol is more than p nitophenol.

Answered by Prachi Sawant | 5th Nov, 2016, 10:01: PM