Functional groups create reactive sites in molecules.
The polar part of a molecule that can hydrogen bond to water is said be hydrophilic.
Pi (π) bonds create active sites and will react with electron-deficient species.
A electronegative heteroatom like nitrogen, oxygen, or a halogen makes a carbon atom electrophilic.
(carbon will have less electronic density, which is attracted by the more electronegative heretoatoms, and it will tend to attract electron rich chemical species, and in this situation we say that the carbon atom is electrophilic).
The nonpolar part of a molecule that is not attracted to water is said to be hydrophobic.
A lone pair on a heteroatom makes it basic and nucleophilic.
(the heteroatom with the lone pair will tend to attract electron poor chemical species, and in this situation we say that the heteroatom is nucleophilic).
