Aldehydes are polar molecules due to the carbonyl group, but have lower boiling points than alcohols and higher than ethers because there is no hydrogen bonding between aldehyde molecules. The carbonyl oxygen allows aldehydes to form strong hydrogen bonds with water molecules, making low molar mass aldehydes more soluble in water through these bonds between the aldehyde oxygen and hydrogen and water oxygen. As molar mass increases, solubility decreases, and lower molar mass aldehydes have a sharper odor while higher molar mass have a more fragrant smell.

1. Aldehydes
 Physical Properties of Aldehydes

2. Because of the carbonyl group , aldehydes
are polar molecules
In this structure , the oxygen atom is not bonded to
a hydrogen , so there is no hydrogen bonding
between aldehyde molecules. Consequently ,they
have lower boiling point than the corresponding alcohols
and higher boiling points than the corresponding ethers

3. The carbonyl oxygen atom allows molecules of
aldehyde to form strong hydrogen bonds with water
molecules Low molar mass aldehydes dissolve in water
due to hydrogen bonding . Hydrogen bonds are formed
between the oxygen atoms and also between the
hydrogen atom of water and also between the hydrogen
atom of the aldehyde and the oxygen atom of water.
 Low molar mass aldehydes are more soluble in
water
 As molar mass increases, solubility decreases
Have pleasing taste and smell
The lower the molar mass aldehydes have sharp odor
As molar mass increases the odor becomes more fragrant