Reference IUPAC Nomenclature Reference
IUPAC Nomenclature Reference
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In this section
This appendix provides a working reference for IUPAC organic nomenclature at the level needed for Organic Chemistry I and II. It is designed to be used alongside Chapter 1 (Functional Groups) and returned to throughout the course as new compound classes are introduced. It is not exhaustive — the full IUPAC system includes preferred names, retained names, and additional rules beyond this handbook’s scope (see “A Note on Ambiguity” below).
The Logic of IUPAC Nomenclature
The IUPAC system is designed so that a compound’s name and structure determine each other unambiguously. The name encodes three things:
The suffix is determined by the highest-priority functional group present. Use the priority order in the table below. If the molecule contains only carbon…
For chains longer than 10 carbons: undec- (11), dodec- (12), tridec- (13), tetradec- (14), pentadec- (15).
Functional Group Priority and Suffixes
When multiple functional groups are present, the one with the highest priority (lowest number in this table) determines the suffix. All lower-priority…
When the same substituent appears more than once, use a multiplying prefix. These are not alphabetized — alphabetize by the substituent name itself.
The double or triple bond position is given the lowest possible locant. The locant refers to the lower-numbered carbon of the multiple bond.
Add the prefix cyclo– before the parent chain name.
- Principal functional group: aldehyde → suffix -al 2. Parent chain: 4 carbons → but- 3. Aldehyde carbon is C-1; no other substituents 4. Name: butanal
Common Name ↔ IUPAC Name Table
The IUPAC system is updated periodically, and two valid IUPAC names sometimes exist for the same compound (particularly for alcohols, where both propan-1-ol…