Nomenclature
IUPAC Naming Conventions
Naming Steps
• Primary goal of international union of pure and applied chemistry naming system is to
create an unambiguous relationship between the name and structure of a compound.
1. Identify the Longest Carbon Chain Containing the Highest-Order Functional Group
• This will be called the parent chain, and will determine the roots of the name
• The highest priority functional group (with the most oxidized carbon) will provide the
suffix
• If there are two or more carbon chains of equal length, then the more substituted chain
gets priority as the parent chain.
2. Number the Chain
• The carbon numbered one will be the one closest to the highest-priority functional
group.
• If the functional groups all have the same priority, numbering the chain should make the
number of the substituted carbons as low as possible
o The more oxidized a carbon is, the higher priority it has in the molecule.
▪ Oxidation state increases with more bonds to heteroatoms (atoms
beside hydrogen and carbon) and decreases with more bonds to
hydrogen.
• For rings, numbers start at the point of greatest substitution, and continues in that
direction
• If there is a tie between assigning priority in a molecule with double and triple bonds,
the double bond takes precedence.
3. Name the Substituents
• Substituents are functional groups that are not part of the parent chain.
• Substituents name will be placed at the beginning of the compound name as a prefix,
followed by the name of the longest chain.
• Only the highest priority functional group will determine the suffix for the compound
• Carbon chain substituents are named like alkanes, with suffix –yl replacing –ane
• n- prefix indicates that it is normal or is a straight chain alkane.
• If there are multiple substituents of the same type, prefixes such as di-, tri- & tetra- are
used.
4. Assign a Number to Each Substituent
• Pair the substituents that you have named to the corresponding number in the parent
chain
• Multiple substituents of the same type will get both the required prefix and a carbon
number designation, even if they are on the same number
5. Complete the Name
• Always begins with the names of the substituents in alphabetical order, and each
substituent is preceded by its number.
