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Nomenclature
Carbon-to-carbon triple bonds in a compound means that a still different ending has to
be used for the name. For a triple bond, we use a -yne
ending. With the exception of the -yne ending, the same naming process is
used as was used for alkenes.
| Let's look at some examples of alkene nomenclature. (These
are also shown in Example 11 in your workbook.) Again, let me emphasize that it is the
same system that you have gone through before but with a differnet ending to represent a
different functional group. |
| When two carbon atoms are present, we have an eth- prefix
and a -yne ending to indicate a triple bond. This compound is named ethyne.
Its common name is acetylene. |
CH º CH
|
ethyne (acetylene) |
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| The alkyne with three carbon atoms is called propyne. |
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| These three are 1-butyne, 2-butyne, and 1-butyne.
Note that it is important to count carbon atoms from the end of the chain closest to the
triple bond. |
| CH º C - CH2
- CH3 |
1-butyne |
| CH3 - C º C
- CH3 |
2-butyne |
| CH3 - CH2 - C º CH |
1-butyne |
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| Again, other functional groups can be added to chains which contain triple
bonds, as shown in this compound, 3-chloro-4-methyl-1-pentyne. |
CH3 - CH - CH - C º CH
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CH3 Cl |
| 3-chloro-4-methyl-1-pentyne |
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Practice
Example 12 will give you some practice naming and drawing structural formulas for
alkynes.
| C - C - C º C - C |
C - C º C - C - C - C
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C |
| 3,3-dimethyl-1-heptyne |
| 2-methyl-5-ethyl-3-octyne |
Answers
| C - C - C º C - C |
2-pentyne |
C - C º C - C - C - C
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C |
4-methyl-2-hexyne |
| 3,3-dimethyl-1-heptyne |
C
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C º C - C - C - C - C - C
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C |
| 2-methyl-5-ethyl-3-octyne |
C - C - C º C - C - C - C - C
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C C - C
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E-mail instructor:
Sue Eggling
Clackamas Community College
©2001, 2003 Clackamas Community College, Hal Bender
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