2. ALKYNES
-Characterized by C C triple bond(s)
-Classified as unsaturated hydrocarbons
-empirical formula = CnH2n-2
(applies when the molecule only has one triple bond)
CnH2n-2, n=5
= C5H8
7. ALKYNES
IUPAC naming system:
Name the following alkynes:
H3C
CH3 CH3 CH3
5 6
1
2
H3C H3C
1 2 3 4 9 7 5 3
8 6 4
CH3
CH3 CH3
4-methylhex-2-yne 5-ethyl-4,6,7-trimethylnon-2-yne
The triple bond has a higher numbering priority
than the alkyl and halide substituents
8. ALKYNES
IUPAC naming system:
Name the following alkynes: H C
2
1 2
5 3
3 4 5 6
H3C 6 4 2
CH
1 7CH3
CH3
hex-4-en-1-yne 3-ethylhept-1-en-4-yne
Alkenes are ordered first in the name, and the “e” ending is
dropped.
Generally, double bonds and triple bonds have equal
numbering priority* (aim to get the lowest numbers).
9. ALKYNES
IUPAC naming system:
Name the following alkynes:
5 3
6 4 4 2
2
H2C1 3 5
1
CH
6
hex-1-en-5-yne or hex-5-en-1-yne
*Double bonds have higher priority than triple bonds
whenever there is ambiguity in their numbers.
11. ALKYNES
IUPAC naming system:
Name the following alkyne:
Cl
H3C 2
1 3
9
Cl
4
H3C 8 5 F
7 6
Cl
F
F
3,4,5-trichloro-8,9-diethyl-5,7,7-trifluorocyclononyne
12. ALKYNES
Drawing alkynes:
Draw the following alkynes using structural diagrams
4,5-dibromohex-2-yne 1,2-dimethylcyclooct-1-en-4-yne
H
H C H H
H H H H H H
H C C C H C C C H
C C C H
H Br Br H H C C H
C C H
H
H C C H
13. ALKYNES
Drawing alkynes:
Draw the following alkynes using line diagrams
non-2-yne non-1-yne
1
8 6 4
8 6 4 2
3
9 7 5
9 7 3
5
2
1
The triple bond cannot bend, so the bonds
adjacent to a triple bond must be straight.
