Chapter 8 · Chemistry
Classifying Organic Compounds
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Millions of organic compounds, one first question: is the carbon chain open, or a ring? How to sort compounds into acyclic, alicyclic, aromatic and heterocyclic.
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Functional GroupsTwo molecules can share the same carbon chain and still behave differently. How one small group of atoms gives a compound its chemical identity: –OH, –CHO, C=O, –COOH and –NH₂.Chemistry · simulation
Key points
- Look at the skeleton first: an open chain, or a ring?
- Acyclic (open-chain, aliphatic): the chain does not close, as in ethane and butane.
- Alicyclic: a ring of carbon atoms, as in cyclohexane.
- Aromatic: benzene and compounds with a benzene ring, such as toluene.
- Heterocyclic: the ring holds another atom, such as oxygen in furan.
- Then look at the functional group.
Sorting compounds
| Compound | Class | Why |
|---|---|---|
| 2-Methylpropane | Acyclic | A branch closes no ring |
| Cyclohexene | Alicyclic | A carbon ring, not a benzene ring |
| Toluene | Aromatic | Has a benzene ring |
| Furan | Heterocyclic (also aromatic) | Oxygen in the ring |
| Tetrahydrofuran | Heterocyclic | Oxygen in the ring, not aromatic |
Try it yourself
Goal: Sort 12 compounds by their skeleton and see why each goes where it does.
- Choose a compound and look at its skeleton.
- Sort it into a class.
- Read the questions that decide it.
- Try cyclohexene, then tetrahydrofuran.
Quick quiz
3 questions. Choose an answer for each, then submit to see your score and the explanations.
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