They are different from alkanes because they can form double(alkene) and triple(alkyne) bonds.
Alkenes are formed with double bonds between carbon atoms and the ending is -ene.
Example.
Let us name this.
If this was an alkane, it would end in -ane and its name would be 2-methylpentane.
However it is an alkene as evidenced by the double bond.
Therefore the name is 4-methyl
Then you write the number of the carbon# the double bond comes after so 2-pent-ene
so the name of this compound is 4-methyl-2-pentene.
Alkynes are exactly the same as alkenes except when you name it, change the ending to -yne. They use triple bonds.
Name this.
First count the parent hydrocarbon.
=4 so Butane.
Then you take into account the triple bond so the name changes to butyne.
Since there are no branched hydrocarbons, nothing needs to be added except the position of the triple bond.
This is added in front of the word butyne
It is 2-butyne.
http://www.youtube.com/watch?v=7XbYhjyUI-M
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