Organic Chemistry
A guide to systematic naming of organic compounds — the rules, the logic, and the order of precedence.
The IUPAC nomenclature of organic chemistry is a systematic method of naming organic chemical compounds. Just kidding about it being simple — it has a large set of rules that require strict memorization. On the positive side, outside of class the rules for complex compounds aren't super important and people generally work from structure. The rules are fully described in the Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013, a 1,500+ page book. With some help from Wikipedia, here's a useful summary.
Step-by-step
Identify the parent hydrocarbon chain. This chain must obey the following rules, in order of precedence:
It should have the maximum number of substituents of the suffix functional group.
It should have the maximum number of multiple bonds.
It should have the maximum number of single bonds.
It should have the maximum length.
Identify the parent functional group, if any, with the highest order of precedence.
Identify the side-chains. Side chains are carbon chains branched off from the parent chain, not part of it.
Identify remaining functional groups and name them by their ionic prefixes (hydroxy for –OH, oxy for =O, etc.). Different side-chains and functional groups are grouped together in alphabetical order. Note: prefixes like di-, tri- are not considered when alphabetizing.
Identify double and triple bonds.
Number the chain. Number in both directions, then choose the numbering that:
Has the lowest-numbered locants for the suffix functional group.
Has the lowest-numbered locants for multiple bonds.
Has the lowest-numbered locants for prefixes.
Number all substituents and bonds with their locants. If more than one of the same substituent exists, add a prefix: di– (2), tri– (3), tetra– (4). Numbers for each type are grouped in ascending order before the name.
Apply punctuation correctly:
Commas between numbers: 2 5 5 → 2,5,5
Hyphens between a number and a letter: 2,5,5 trimethylheptane → 2,5,5-trimethylheptane
Successive words are merged: trimethyl heptane → trimethylheptane
Final format
The finalized IUPAC name follows this structure, with side chains and secondary functional groups arranged alphabetically:
Name structure
#,#-di[side chain]-#-[secondary functional group]-#-[side chain]-#,#,#-tri[secondary functional group][parent chain prefix]-#,#-di[double bonds]-#-[triple bonds]-#-[primary functional group]
# denotes a locant number. di– follows #,#; tri– follows #,#,#. If all bonds are single bonds, use "ane". Double bonds (en) are written before triple bonds (yne).