Acyclic or open chained compounds:
- Also called aliphatic compounds.
- Consist of straight or branched compounds.
Alicyclic or closed chained compounds:
- Also called aliphatic cyclic.
- Carbon atoms are bonded in the form of a ring.
- Homocyclic – consisting only of carbon atoms joined in the ring.
- Heterocyclic – consist of atoms other than carbon joined in the ring.
- Benzenoid: These compounds consist of at least one benzene ring, i.e., a six-membered carbocyclic ring having alternate single and double bonds. Generally, these compounds have some fragrant odour and hence, named as aromatic (Greek word aroma meaning sweet smell).
- Non-benzenoid aromatics: There are aromatic compounds, which have structural units different from benzenoid type and are known as Non-benzenoid aromatics
Ex: Tropolone, azulene etc.
- It is an atom or group of atoms responsible for the characteristic chemical properties of the compounds.
Ex: (-OH) group – alcohol
(-CHO) group – aldehyde
- Compounds containing a common functional group.
- The successive members differ by a –CH2 unit.
Ex: Alkanes – methane, ethane, propane
Alkanols – methanol, ethanol, propanol