1. Primary alcohols: These are alcohols in which the carbon atom bonded to the -OH group is attached to only one other carbon atom. When primary alcohols are oxidized, they form aldehydes.

2. Secondary alcohols: These are alcohols in which the carbon atom bonded to the -OH group is attached to two other carbon atoms. When secondary alcohols are oxidized, they form ketones.

3. Benzylic alcohols: These are alcohols in which the carbon atom bonded to the -OH group is attached to a benzene ring. When benzylic alcohols are oxidized, they form benzaldehydes.

4. Allylic alcohols: These are alcohols in which the carbon atom bonded to the -OH group is attached to a carbon-carbon double bond. When allylic alcohols are oxidized, they form enals.