Naming Organic Compounds
Alkanes
H
H
CH3 H
C
C
C
H
H
H
H
2-methylpropane
Rules
1. Pick longest Carbon chain
2. Number from end so the SUM of substituent groups is smallest
3. Substituents should be arranged alphabetically
Example 1
H
H
H
C
C
H
H
H
H
H
3
C
H
4
C
H
5
H
2
C
1
C
C
H
H
6
C
H
H
7
C
H
H
CH3
H
H




Longest chain 7 long, chose to “go round the corner” on the chain as that was the simplest
method for substituents.
2 substituents smallest numbering method results in
2 – methyl
3 – ethyl
Full name is:
3-ethyl-2-methylheptane
Questions
H
H
H
H
C
C
C
H
H
H
H
C
H
C
H
C
H
H
H
H
C
H
H
H
C
C
C
C
H
H
CH3 H
H
H
H
C
C
H
C
H
H
H
C
CH3
H
H
H
H
H
H
C
H
H
C
C
C
C
H
H
C
H
H
C
H
H
H
H
H
H
C
C
C
C
H
CH3 H
H
H3C
C
H3C
C
H3C
C
H3C
H3C
H3C
H
H
H
CH3 H
H
H H H
C
H H H
H
H C C C C C H
H
H
H
C
C
H
H H H
H H
H
C
H
H
H
H
H
H
C
C
H
CH3
CH3
CH3
CH3
CH3
CH3
H H
H H H
C
H
H
C C
C C H
H
H
H C
H
H H H
H
H
H
C
H
H
H C C C
H
C H
H
H H
C
H
H
H
H H
H
H
C
C
C
C
H
H
H
H
H
CH3 CH3
H
C
C
H
H
C
H
H
H
C
H
C
H
H
H
C
C
C
H
H
H
H
C
H
H
H
H
H
C
H
H
H
C H C
H
H
H H
C C H
H C C
C C C H
H H
H
H
H
C
H
H
H
H
H
C H
H C
CH3 CH3
H
Alkenes
Alkenes have another level of isomerism as the double bond cannot rotate, therefore if both carbons
are attached to two different then they are said to exhibit E/Z isomerism (commonly referred to as
cis-trans isomerism)
H3C
H3C
CH CH
CH3
CH CH
CH3
E-but-2-ene
Z-but-2-ene
In cis – trans terms


The cis-isomer is the Z isomer (Z comes from Zusammen, for together)
The trans-isomer is the E isomer (E comes from entgegen, opposite
The terms have to be applied carefully as the attached groups are given priorities dependant on
their atomic number if the highest priority groups are on the same side then they are known as Zisomers and if they are opposite then they are E-isomers
H3C
1
Cl
C
2
1
H3C
C
C
2
H
1
2
CH3
Z-2-chlorobut-2-ene
H
2
CH3
C
Cl1
E-2-chlorobut-2-ene
Alkene substituents
H
H
H
C
H
C
H
H
C
1-butenyl
C
H
H
H
H
H
C
C
2-butenyl
C
C
H
H
H
H
H
C
C
H
H
C
H
H
C
H
3-butenyl
Questions
H
H
H
C
H
H
H
C
C
C
H
H
H
C
C
H
C
H
H
H
H
C
H
H
C
C
H
C
H
H
H
C
H
H
H
H
H
H
C
H3C H
H
C
C
C
C
H
H
C
H
H
C
C
H
H
C
C
H
C
CH3 H
H
H
H
H
H
C
H
C
H
H
H
C
C
C
H
C
C
H
C
C
H
H
H
H
H
H
C
H
H
C
H
H3C
H
H
H
C
H
C
C
H
H
C
C
H
C H
H H
H
H
C
H
H
H
H C
C
C
H
H
C
H
C
C
C
H
H
H
H
H
H
H
H
C
H
H
C
H
H
H H
H
C
H
C
H
C
C
H
H
C
H
H
H
C
H
H
C
C
C
Do E/Z isomers exist here?
H
H
H
C
C
H
H
H
H
CH3
H
C
H H
H
Functional groups
Organic chemistry also investigates other substituents on these carbon chains. There are many
different possible substituents. We will be looking at some of the most important functional groups.
To name organic compounds and explain which functional group follow a similar course to the
method used for alkanes and alkenes.




Deduce the functional group
Find the longest chain
Number from the end so that the SUM of the substituents are smallest
Arrange substituents alphabetically.
Type of compound
Alkane
Formula
Prefix
Suffix
-ane
C
C
Alkene
-ene
C
C
C
Cyclic*
-cyclo(size of
ring)ane/ene
C
C
F
Cl
Br
I
OH
O
Halogenoalkane
Alcohol
Aldehyde*
FluoroChloroBromoIodoHydroxy-
-ol*
-al
C
H
O
Ketone*
Oxy(used very rarely)
C
-one
O
Carboxylic acid*
-oic acid
C
OH
O
Ester*
Alkyl (i.e. methyl,
ethyl, propyl etc)
C
O
-oate
C
If multiple functional groups exist the name must explain where and how. The suffixes are preceded
by di, tri, tetra, penta, hexa… for 2, 3, 4, 5, 6… identical functional groups
Cl
Br Br Br Br Cl
H
H
H
H
C
C
C
C
C
C
C
C
C
Cl
Cl
Cl
H
Cl
H
H
F
H
H
1,2,3,4-tetrabromo-1,1,2,3,5,5-hexachloro-8-fluorononane

Functional groups marked with * do not get numbered according to the SUM of the substituents rather
from the end of the chain with the functional group on. The chain must also end in the functional group even if
it is not the longest.
Questions
Cl
H
H
H
C
C
C
H
H
H
Cl
H
H
C
C
H
H
H
O
Cl
H
C
H
Cl
H
C
C
C
H
Cl
H
H
Cl
H
H
O
OH
H C H H
C
C
C
H
H
C
C
C
H
H
H
F
Cl
H
C
C
C
H
Cl
F
H
Cl
H
H
C
H
H
OH
C
C
H
H
F
O
C
H
H
H
H
O
H
C
C
H
C
H H
Cl
C
H
C
H
H
C
H
Cl
H
C
H
OH
Cl
H
H
C
C
C
O
C
H
Cl
H
O
H
H
C
H
C
H
H
H
F
C
F
C
C
Br
Cl
H
H
H
F
C
H
I
C
C
H
H
I
C
F
C
Cl
I
Br
C
I
Br