← Organic compounds
3 Functional group reference
Every organic question starts with recognising the functional group. Learn this table cold, the suffix/prefix drives naming, and the group drives the reactions.
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Level 3 functional groups
| Class | Group | Example (condensed) | Suffix / prefix |
|---|
| Alkane | C–C only | CH₃CH₃ ethane | -ane |
| Alkene | C=C | CH₂=CH₂ ethene | -ene |
| Haloalkane | C–X (F,Cl,Br,I) | CH₃CH₂Br bromoethane | halo- prefix |
| Alcohol | –OH | CH₃CH₂OH ethanol | -ol |
| Aldehyde | –CHO (end) | CH₃CHO ethanal | -al |
| Ketone | C=O (middle) | CH₃COCH₃ propanone | -one |
| Carboxylic acid | –COOH | CH₃COOH ethanoic acid | -oic acid |
| Ester | –COO– | CH₃COOCH₃ methyl ethanoate | -yl -oate |
| Amine | –NH₂ | CH₃CH₂NH₂ ethylamine | -amine / amino- |
| Amide | –CONH₂ | CH₃CONH₂ ethanamide | -amide |
| Nitrile | –C≡N | CH₃CN ethanenitrile | -nitrile |
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Mnemonic: suffix priority order
“All Excellent Alchemists Need A Keen Analytical Approach” →
Acid ·
Ester ·
Amide ·
Nitrile ·
Aldehyde ·
Ketone ·
Alcohol ·
Amine. (Alkene/alkyne and halogens never win: they’re always prefixes or the parent chain.)
Naming priority (which group gets the suffix)
- Priority order (highest first): carboxylic acid > ester > amide > nitrile > aldehyde > ketone > alcohol > amine > alkene.
- The highest-priority group takes the suffix and lowest locant; everything else becomes a prefix (hydroxy-, oxo-, amino-, halo-).
- Alkene/alkyl chains and halogens are always prefixes or the parent chain.