In organic molecules, the atoms are linked by covalent bonds. Organic molecules are generally large and may be complex, involving many such bonds. Inorganic compounds have considerably simpler structure in terms of number, but not necessarily type, of bonds. In organic molecules, to a first approximation, we may say that one bond does not affect another. Thus an atom such as a chlorine atom, -Cl, or a group of atoms such as the alcohol group, -OH, on one end of a molecule will behave chemically in the same way almost without regard to the molecule to which it is covalently attached. The idea of different independent or semi-independent atoms or groups of atoms on the same molecule is central to our modern understanding of organic chemistry. It is called the concept of functional groups. The nomenclature of organic compounds, like most of the rest of our understanding of reactions of organic compounds, is based upon the concept of functional groups.
