Name the following alkenes:

SOLUTION:

Molecule 1.

1. Main chain: 4 carbons with double bond (butene)
2. Numbering: lowest locant to the double bond.
3. Substituents: no
4. Name: But-1-ene

Molecule 2.

1. Main chain: 5 carbons with double bond (pentene)
2. Numbering: lowest locant to the double bond.
3. Substituents: no
4. Name: Pent-2-ene

Molecule 3.

1. Main chain: 4 carbons with two double bonds (butadiene)
2. Numbering: double bonds at the same distance from the ends, we number so that methyl takes the lowest locant.
3. Substituents: methyl in position 2 .
4. Name: 2-Methylbuta-1,3-diene

Molecule 4.

1. Main chain: 9 carbons with two double bonds ( nonadiene )
2. Numbering: lowest locant to the double bonds ( 2,6 ).
3. Substituents: methyls in position 4,7 .
4. Name: 4,7-Dimethylnon-2,6-diene

The longest chain containing the greatest number of double bonds is chosen as the main chain.

Molecule 5.

1. Main chain: 6 carbons with two double bonds (hexadiene). Note that it is not the longest.
2. Numbering: lowest locant to the double bonds ( 1,4 ).
3. Substituents: 2 -position ethyl and 5 -position methyl.
4. Name: 2-Ethyl-5-methylhexa-1,4-diene

Molecule 6.

1. Main chain: 8 carbons with two double bonds (octadiene)
2. Numbering: lowest locant to the double bonds ( 1,4 ).
3. Substituents: methyls in position 7,7 .
4. Name: 7,7-Dimethylocta-1,4-diene


The main chain is numbered so that the double bonds take the minor locants.