Hydrocarbons

Hydrocarbons

The above figure is an example of a hydrocarbon

Hydrocarbons are compounds that are predominately composed of Hydrogen and Carbon atoms.
There are many different types of compounds that are predominately hydrocarbon in structure but have other functional groups. Examples of this type would be cholesterol, fatty acids and phospholipids.
The covalent bonds between the Carbon and Hydrogen atoms are nonpolar covalent bonds.
With nonpolar covalent bonds, unkike polar covalent bonds, there is an equal sharing of electron between the Carbon atoms and the Hydrogen atoms.
Thus, there is no charge separation in the molecule and it cannot form hydrogen bonds with water.

Hydrophobic Interactions

Hydrophobic interactions are more correctly called hydrophobic exclusions.

In the figure above and to the left, there are two regions containing hydrophobic substances.
Each of the substances is excluded from the water matrix.
Over a period of time the two areas of hydrophobic substances will encounter one another, combine and form one larger hydrophobic region that is excluded from the water matix.
This combined state is more energetically favorable than the one in which the hydrophobic substances were separate. Thus this combined state will persist.