What are the physical properties of aldehydes and how do they differ from ketones?

Aldehydes have distinct physical properties from ketones due to their structural differences.

Aldehydes and ketones are both organic compounds that contain a carbonyl group, which is a carbon atom double-bonded to an oxygen atom. However, aldehydes have the carbonyl group located at the end of a carbon chain, while ketones have the carbonyl group located in the middle of a carbon chain.

One of the physical properties that differ between aldehydes and ketones is boiling point. Aldehydes have lower boiling points than ketones due to the presence of a hydrogen atom attached to the carbonyl group, which allows for intermolecular hydrogen bonding. Ketones lack this hydrogen atom, resulting in weaker intermolecular forces and a higher boiling point.

Another physical property that differs between aldehydes and ketones is solubility in water. Aldehydes and ketones with fewer than five carbon atoms are soluble in water due to the ability of the carbonyl group to form hydrogen bonds with water molecules. However, as the carbon chain length increases, solubility decreases. Aldehydes are generally more soluble in water than ketones due to the presence of the hydrogen atom on the carbonyl group.

In addition, aldehydes have a distinct odour that is often described as pungent or fruity, while ketones have a sweet, acetone-like odour.

Overall, while aldehydes and ketones share some physical properties due to their carbonyl group, their structural differences result in distinct physical properties.