Question

Why do amines generally have lower boiling points than alcohols of comparable molar mass?

Answer 1

Hint: To solve this question, first we have to focus on the factors that determine the boiling point of the organic substances, then we will compare that particular property of both the organic compounds i.e. amines and of alcohols.

Complete Step By Step Answer:
So, as we know from above, we have to compare the boiling points of two organic compounds i.e. of amines and of alcohols.
So, the boiling point of a substance depends upon the bonding present between them or the hydrogen bonding.
The strength of the hydrogen bonding determines the boiling point of the organic compound, the more the intermolecular force of hydrogen bonding, the higher the boiling point is and the less the strength of hydrogen bonding present in the molecule, the lower the boiling point is.
So as we can see in the amines the hydrogen bond is formed between the Nitrogen atom of amine and the Hydrogen atom of water whereas in the case of alcohols the hydrogen bond is formed between the Oxygen atom of the alcohol and the Hydrogen atom of the water molecule.
So , obviously the $ O - H $ bond present in alcohol is stronger than the $ N - H $ bond present in the amine and thus as a consequence , alcohols have higher boiling points than amines of comparable molar mass.

Note:
The strength of intermolecular hydrogen bonding present in the compound is defined by its electronegativity difference between the atom, thus, Oxygen is more electronegative atom than Nitrogen atom, thus have more electronegativity difference with hydrogen atom and has a stronger hydrogen bonding.