Alkanes:

Contain only single bonds

Alkenes:

Contain at least one double bond

Alkynes:

Contain at least one triple bond

Aromatics:

Contain a benzene ring, a 6 carbon ring with alternating single and double bonds.

Alcohols:

Contain a hydroxyl group (O-H) off of a carbon

Phenols:

Contain at least one hydroxyl group (O-H) attached directly to a benzene ring

Carboxylic Acids:

Contain a double bonded oxygen and a hydroxyl (O-H) attached to the same carbon.

Ketones:

Contain a double bonded oxygen to a carbon.

Aldehydes:

Contain a double bonded oxygen attached to a carbon. Differ from Ketones by carbonyl (C=O) located at the end of the chain.

Esters:

Contain a double bonded oxygen and a single bonded oxygen attached to the same carbon.