C C
O
C C
H H
C C
H X
C C
H OH
C C
OH OH
C C
X OH
C C
X X
C O O C
C C
Halohydrin
HOX
HOOH
O 3
O 2
Pt-C or Pd-C
Alkyl halide
H 2
HX
H 2 SO 4 , heat
Hydration
H 2 O
Alkane
Alcohol
Diol
Aldehyde or ketone
Epoxide
Hydrogenation
Hydroxylation
Ozonolysis
Epoxidation
Halogenation
Halohydrin
formation
Hydrogen halide
addition
X 2
Dihalide
+
Alkene
4.5 Alkynes and their derivatives
Alkynes are hydrocarbons that contain a carbon–carbon triple bond. A triple
bond consists of a s bond and two p bonds. The general formula for the
alkynes is C n H 2nÀ2 . The triple bond possesses two elements of unsaturation.
Alkynes are commonly named as substituted acetylenes. Compounds with
triple bonds at the end of a molecule are called terminal alkynes. Terminal
À ÀCH groups are called acetylenic hydrogens. If the triple bond has two
alkyl groups on both sides, it is called an internal alkyne.
C
H CH
CH 3 CH 2 C CCH 3
CH 3 CH 2 C CH
1-Butyne (ethylacetylene)
Terminal alkyne
2-Pentyne (ethylmethylacetylene)
Internal alkyne
Ethyne (acetylene)
1
3
4
2
1
3
4
5
2
4.5.1 Nomenclature of alkynes
The IUPAC nomenclature of alkynes is similar to that for alkenes, except
the –ane ending is replaced with –yne. The chain is numbered from the end
closest to the triple bond. When additional functional groups are present, the
suffixes are combined.
CH 3 CH 2 CHC CH
CH 3 C CCHCH 2 CH 3
CCHCH 2 CH 3
CH 3 CHC
CH 3
OH
Br
OCH 3
1-Pentyn-3-ol
4-Methoxy-2-hexyne
5-Bromo-2-methyl-3-heptyne
1
6
5
7
1
3
4
2
5
3 4
2
1
3 4
2
5
6
4.5.2 Structure of alkynes
The triple bond consists of one s bond and two p bonds. Each carbon is
bonded to two other atoms, and there are no nonbonding electrons. Carbon
108
CH4 ORGANIC FUNCTIONAL GROUPS
O
C C
H H
C C
H X
C C
H OH
C C
OH OH
C C
X OH
C C
X X
C O O C
C C
Halohydrin
HOX
HOOH
O 3
O 2
Pt-C or Pd-C
Alkyl halide
H 2
HX
H 2 SO 4 , heat
Hydration
H 2 O
Alkane
Alcohol
Diol
Aldehyde or ketone
Epoxide
Hydrogenation
Hydroxylation
Ozonolysis
Epoxidation
Halogenation
Halohydrin
formation
Hydrogen halide
addition
X 2
Dihalide
+
Alkene
4.5 Alkynes and their derivatives
Alkynes are hydrocarbons that contain a carbon–carbon triple bond. A triple
bond consists of a s bond and two p bonds. The general formula for the
alkynes is C n H 2nÀ2 . The triple bond possesses two elements of unsaturation.
Alkynes are commonly named as substituted acetylenes. Compounds with
triple bonds at the end of a molecule are called terminal alkynes. Terminal
À ÀCH groups are called acetylenic hydrogens. If the triple bond has two
alkyl groups on both sides, it is called an internal alkyne.
C
H CH
CH 3 CH 2 C CCH 3
CH 3 CH 2 C CH
1-Butyne (ethylacetylene)
Terminal alkyne
2-Pentyne (ethylmethylacetylene)
Internal alkyne
Ethyne (acetylene)
1
3
4
2
1
3
4
5
2
4.5.1 Nomenclature of alkynes
The IUPAC nomenclature of alkynes is similar to that for alkenes, except
the –ane ending is replaced with –yne. The chain is numbered from the end
closest to the triple bond. When additional functional groups are present, the
suffixes are combined.
CH 3 CH 2 CHC CH
CH 3 C CCHCH 2 CH 3
CCHCH 2 CH 3
CH 3 CHC
CH 3
OH
Br
OCH 3
1-Pentyn-3-ol
4-Methoxy-2-hexyne
5-Bromo-2-methyl-3-heptyne
1
6
5
7
1
3
4
2
5
3 4
2
1
3 4
2
5
6
4.5.2 Structure of alkynes
The triple bond consists of one s bond and two p bonds. Each carbon is
bonded to two other atoms, and there are no nonbonding electrons. Carbon
108
CH4 ORGANIC FUNCTIONAL GROUPS