Drawing hydrocarbon skeletons and appreciating the variety of ways in which carbon atoms can be bonded to each other is a good introduction to organic chemistry because all organic compounds are hydrocarbons in part.
Both saturated and unsaturated hydrocarbons (
1,
2) can have the same carbon skeleton.
Most organic compounds contain bonds from carbon to atoms other than H.
3 and
4 are two examples that have the same carbon skeleton as
1.
1  | 2 |
3 | 4 |
Compounds
5,
6,
7 and
8 have the same carbon skeleton.
These illustrate that carbon-oxygen double bonds are very common in organic compounds.