IUPAC Nomenclature
of
Organic Compounds
(Part 2)
I. Naming Alkenes and Alkynes
(Unsaturated Compounds)
Alkanes contain single bonds only
-ANE ending
CnH2n+2
(saturated)
Alkenes contain a double bond
CnH2n
Alkynes
CnH2n-2
-ENE ending
(unsaturated)
contain a triple bond between
(unsaturated)
-YNE ending
Naming Alkenes & Alkynes
Name & position
of branching
groups
(if any)
+
Indicate where
double or triple
bond is located
+
Change the
ending of the
parent name to
- ene or -yne
Parent Name = longest continuous chain of
carbon atoms
Use Greek prefixes to indicate the presence
of multiple identical branching groups.
4
C
1
2
3
C
2
What is the parent name?
C
3
1
C
4
Butene (double bond present)
Must number parent chain so the carbon atoms containing
the double bond have the lowest number. Use the lowest
number to indicate where the double bond starts.
What position is the double bond located ? 1 position
Correct name is : 1-butene
Note: Carbon atoms can only have four bonds
6
5
4
CH3CH CH
1
2
3
3
2
CH
4
CH
CH3
5
6
CH3
CH3
What is the parent name?
1
hexene (double bond present)
What position is the double bond located ?
Location and number of groups:
3 position
2,5-dimethyl
Correct name is : 2,5-dimethyl-3-hexene
Note: Always number so the double bond gets the lowest number
(CH3)2C=CHCH2C(CH3)3
(CH3)2C=CHCH2C(CH3)3
2,5,5 – trimethyl-2-hexene
(CH3CH2CH2)2C=CH2
(CH3CH2CH2)2C=CH2
2-propyl-1-pentene
Hydrocarbons can also contain other atoms, such as
halogens (F, Cl, Br, I). Halogen atoms are treated
like branching alkyl groups.
Halogen
Group Name
F
fluoro
C
chloro
Br
bromo
I
iodo
1
2
3
4
5
6
Longest chain containing triple bond?
7
2-heptyne
(triple bond)
Location and number of groups?
4-methyl
5-ethyl
6-chloro
Name: 6-chloro-5-ethyl-4-methyl-2-heptyne
4-bromo-5-methyl-2-hexyne
6-chloro-3,3-dimethyl-4-octyne