Part 3: Basics of Organic Chemistry—Overview

Organic chemistry is the study of the carbon atom. While it may seem simple to study just one of the many elements that exist in nature, the carbon atom is actually very important to the world around us. In fact, carbon is so important that it is considered the chemical basis of all known life! Other elements such as hydrogen, oxygen, nitrogen, and sulfur are also important in organic chemistry, but occur far less frequently than do carbon atoms.

Every carbon atom has four electrons in its valence shell, so it needs four more electrons to maximize stability (remember that atoms are most stable when their valence shell is completely full, which occurs when eight electrons are present). It can gain these four electrons by forming four covalent bonds with other elements. The basic structure of all organic molecules is what is called a hydrocarbon chain. It includes a series of carbon atoms bonded together with all extra bonding spaces filled in by hydrogen. The structure of this backbone changes depending on the type of compound—it can be a chain or a ring, branched or straight. Bonds between carbon and hydrogen atoms are very stable, making hydrocarbons chemically unreactive.

Connected to the hydrocarbon backbone, an organic molecule may have a functional group or groups composed of non-carbon atoms such as oxygen, nitrogen, or sulfur. Bonds between carbon and functional atoms are much less stable, giving them a higher reactivity. In other words, these groups are called “functional” because they do just that—they increase an atom’s reactivity and in turn, give the molecule a specialized function. Although at first it may seem as if there are endless possible combinations of atoms that could come together to form molecules, there are just a few common patterns of chemical structures that exist in nature. Included below is a diagram of the most common types of functional groups. Most of these groups are also found in essential oils.