Molecules containing only carbon and hydrogen Are major components of fossil fuels produced from the organic remains. Are not prevalent in living organisms. Have a diversity of carbon skeletons which produce molecules of various lengths and shapes. As in hydrocarbons, a carbon skeleton is the framework for the large diverse organic molecules found in living organisms. Compounds with the same molecular formula but with different structures and hence different properties.
Isomers are a source of variation among organic molecules.
There are three types of isomers 1. Isomers that differ in the covalent arrangement of their atoms Number of possible isomers increases as the carbon skeleton size increases. May also differ in the location of double bonds 2. Isomers which share the same covalent partnerships, but differ in their spatial arrangements. Result from the fact that double bonds will not allow the atoms they join to rotate freely about the axis of the bonds.