| Class | Functional Group | Structure | Suffix / Prefix |
|---|---|---|---|
| Alkane | Alkyl (C-C) | - | -ane |
| Alkene | Alkenyl (C=C) | >C=C< | -ene |
| Alcohol | Hydroxyl | -OH | -ol |
| Aldehyde | Carbonyl (terminal) | -CHO | -al |
| Ketone | Carbonyl (internal) | >C=O | -one |
| Carboxylic acid | Carboxyl | -COOH | -oic acid |
| Ester | Ester | -COO- | -oate |
| Amine | Amino | -NH₂ | -amine |
| Amide | Amido | -CONH₂ | -amide |
| Halogenoalkane | Halogeno | -X (F, Cl, Br, I) | fluoro- / chloro- etc. |
| Ether | Alkoxy | -O- | alkoxy- (prefix only) |
Nomenclature Distinction
Class vs Homologous Series
All molecules with the same functional group belong to the same class (e.g. all alcohols). A homologous series is a specific sub-family of that class differing by successive -CH₂- units (e.g. primary straight-chain alkan-1-ols: methanol, ethanol, propan-1-ol...).
Examiner Trap
Class Name vs Functional Group Name
The IB strictly tests the distinction between class names and functional group names:
- Class = Alcohol → Functional group name = Hydroxyl (
-OH) - Class = Carboxylic acid → Functional group name = Carboxyl (
-COOH) - Class = Aldehyde / Ketone → Functional group name = Carbonyl (
C=O) - Class = Amine → Functional group name = Amine / Amino (
-NH₂) - Class = Amide → Functional group name = Carboxamide (
-CONH₂)
Examiner Trap
Distinguishing Amines from Amides
Amines contain -NH₂ attached to a saturated carbon (e.g. CH₃CH₂NH₂, ethylamine).
Amides contain -CONH₂ where the nitrogen is bonded directly to a carbonyl carbon (e.g. CH₃CONH₂, ethanamide). Do not confuse these two functional groups.
AQA GCSE & IB Chemistry
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