Question
The boiling points of carbonyl compounds are higher than the non-polar alkanes but lower than that of alcohols of comparable molecular mass. Give reasons.
Solution
(i) The boiling points of aldehydes and ketones are higher than the boiling points of nonpolar alkanes because dipole-dipole attractions between the molecules of carbonyl compounds are much stronger than the Van der Waals forces which operate between the molecules of alkanes of comparable molecular mass.
(ii) The boiling points of aldehydes and ketones are lower than the boiling points of alcohols because the dipole-dipole interactions between the molecules of carbonyl compounds are weaker than the intermolecular hydrogen binding in alcohol molecules of comparable molecular mass.
