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Nomenclature and Funtional Group Priorities
Useful Concepts
Nomenclature Summary / Group Priority
This section contains the basic IUPAC rules for nomenclature and a table of functional groups
in priority order, with examples.
For a complete introduction to organic nomenclature : Basic IUPAC Organic Nomenclature
Naming branched chain alkanes (the IUPAC way....)
Find the parent hydrocarbon. This is based on the longest continuous carbon chain. If
there are chains of equivalent length, then select the one with the most branch points as
the parent.
Number the atoms in the parent chain, beginning at the end nearer the first branch point.
If there is branching an equal distance from both ends, then consider the next branch
point (repeat as required).
Identify and number the substituents. Remember there must be as many numbers as
there as substitutents.
Write out the name as a single word, using hyphens to separate the different prefixes and
commas to separate the numbers. If two or more different substitutents are present, cite
them in alphabetical order. With identical substituents, use the prefix di­, tri­, tetra­ etc. as
required. Ignore these prefixes when alphabetising.
If a substituent has subranching (ie. its complex) then reapply the first 4 steps as if it were
a compound. Numbering must begin at the point of attachment. Now set this substituent
in parentheses.
Naming the parent chain:
Here is a list of the root names for the hydrocarbon chains of C1 to C12 and a few other
biologically important chains:
C1 = meth­
C2 = eth­
C3 = prop­
C4 = but­
C5 = pent­
C6 = hex­
C7 = hept­
C8 = oct­
C9 = non­
C10 = dec­
C11 = undec­
C12 = dodec­
C16 = hexadec­
C18 = octadec­
C20 = icos­
Functional Groups and Priorities:
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Nomenclature and Funtional Group Priorities
Here is a list of important functional groups arranged in decreasing priority order. All the
structures can be manipulated using JMOL
This priority order is important in nomenclature as the higher priority group is the principle
functional group and it is typically numbered such that is has the lowest number (the locant). You need to learn to recognise these functional groups not just for nomenclature but in order to
recognise their reactions later. In each case the fundamental functional group unit is shown, it is this that you need to be able
to recognise ­ pay attention to the atoms involved and the bonding patterns.
Functional
Group
Formula
Structure
Carboxylic Acids
Acid Anhydrides
Esters
Acyl Halides
Amides
Nitriles
Aldehydes
Ketones
Alcohols
Thiols
Amines
Ethers
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Nomenclature and Funtional Group Priorities
Sulphides
Alkenes
Alkynes
Alkyl Halides
Nitro
Alkanes
© Dr. Ian Hunt, Department of Chemistry, University of Calgary
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