Alkenes and Alkynes

Alkenes have double carbon bonds and Alkynes have triple carbon bonds. Multiple bonds form fewer hydrogens are attached to the carbon atoms. The naming rules are almost the same as with alkanes. ( The position of the double/triple bonds always has the lower possible number and is put in front of the parent chain.)

• Double bonds (Alkenes) has the suffix -ene
• Triple bonds (Alkynes) has the suffix -yne

2 Butene

This is called 2 Butene because there is one double bond so the suffix ends in -ene, and there is also 4 carbons therefore the prefix is but-. The number 2 determines which carbon the double bond takes place. (bonds are in between 2 carbons so we take the lowest possible number)

4  methyl 1 pentyne

This is called 2 methyl 1 pentyne because there is one triple bond so the suffix ends in -yne, and there is also 5 carbons (longest chain) therefore the prefix is pent-. The number 1 determines which carbon the triple bond takes place. (bonds are in between 2 carbons so we take the lowest possible number) Since the carbon with the triple bond is at 1, counting to the left, methyl should be at 4. The name would be 4 methyl 1 pentyne.

Multiple bonds

 1,2 propadiene

This has 2 triple bonds so determine where the bonds take place. 1 and 2. prefix is propa for 3 carbons, and suffix in -ene because its a double bond. Since there is 2 double bonds we need a multiplier in between. di. 

Trans and Cis

 If two carbon bonds are bonded by a double bond and have side chains on them, two possible compounds are possible.