The 5-step algorithm for naming any organic compound systematically.
📋 The IUPAC Algorithm
Find the longest continuous carbon chain containing the highest-priority
functional group → root name (meth-, eth-, prop-, but-, pent-, hex-...)
Number the chain so the principal functional group gets the lowest
possible locant
Add the suffix for the principal group (–ol, –al, –one, –oic acid, –amine,
–amide)
Name substituents as prefixes (methyl-, ethyl-, chloro-, hydroxy-) with locants
List prefixes alphabetically. Ignore di-, tri-, etc. When ordering
Carbon Chain Roots
C atoms
1
2
3
4
5
6
7
8
Root
meth-
eth-
prop-
but-
pent-
hex-
hept-
oct-
⚠️ Common Examiner Traps
Hidden longest chains. The chain may bend at 90° in the drawing; it's still
continuous!
Impossible names. "4-methylpentane" is wrong; numbering from the other end
gives 2-methylpentane
Redundant locants. Don't write "1-butanol" when the –OH can only be at
position 1
Terminal groups are always C-1. Aldehydes (–CHO) and carboxylic acids (–COOH) must be at carbon 1. Write butanal, not butan-1-al; write propanoic acid, not propan-1-oic acid