Why is pyridine soluble in water, whereas benzene is not?

1 Answer
Dec 5, 2015

Answer:

Pyridine is an aromatic heterocyclic base that can effectively hydrogen bond with the water molecule. Benzene has no such facility.

Explanation:

Pyridine, #C_6H_5N#, features a nitrogen centre that is more electronegative than the carbocyclic carbons of the benzene ring. On this nitrogen centre, while the lone pair is delocalized somewhat around the ring, it is still available for H-bonding to the water molecule, and it is quite miscible with water. Benzene has no such heteroatom present, and has very limited water solubility.

On a practical level, I can report that I have found few things that smell as offensively as pyridine. Amines smell pretty foul, but the odour of pyridine makes me quite ill.