There are more compounds composed of carbon than any other element. Since carbon is always found in organic (living) compounds, the chemistry of carbon is referred to as organic chemistry. Carbon is the key element in plastics, synthetic fibers, foods, medicines, and all petroleum products. Petroleum products are composed of hydrogen and carbon and are called "hydrocarbons." The oil used to make petroleum products came from once living things that died long ago. So petroleum is considered "organic" chemistry because the oil which made the petroleum products came from once living things. The only carbon compounds that do not exist in living things are carbon monoxide and carbon dioxide. These two are the only carbon compounds which are not considered organic.
Carbon forms so many compounds because it has four valence electrons. Carbon has
an atomic number of six. Therefore, it has two electrons in its first energy
shell and four in its outer energy shell. Since carbon wants eight electrons in
its outer energy shell it has the potential to form four covalent bonds with other
carbon atoms or with different atoms. The valence electron configuration of
carbon allows it to bond chemically with almost all other elements.
Carbons often bond with hydrogen to form hydrocarbons. Hydrocarbons are compounds which contain only hydrogen and carbon. The simplest hydrocarbon is methane. Methane is CH4. Other hydrocarbons are: ethane--C2H6, propane--C3H6, butane--C4H10, pentane--C5H12, hexane--C6H14, heptane--C7H16, octane--C8H18, nonane--C9H20, decane--C10H22. The number of carbons tells you how many carbons are in the back bone of the compound. The hydrocarbons with a short backbone consisting of 1-5 carbons are gases. Those having 6-20 carbon backbones are liquid. Those having above 20 carbons tend to be solids such as waxes.
Many different compounds can be made from hydrocarbons by replacing one of the hydrogens with a different functional group. A functional group is an atom or a group of atoms that replaces one or more hydrogens in a hydrocarbon. An example of a functional group is the hydroxyl ion (OH-). When the hydroxyl ion replaces one of the hydrogens in a hydrocarbon, it forms an alcohol.
The organic compounds which are most important to living things are carbohydrates.
Carbohydrates are composed of carbon, hydrogen and oxygen and include: sugars,
starch and cellulose. The carbohydrates are used by living things for energy.
The main carbohydrate used by animals to produce energy is glucose--C6H12O6. Table
sugar is called sucrose and is produced from sugar cane. Its molecular formula
is C12H22O11. Starch is a long chain of sugar molecules used by plants to store
energy. Starch is converted to glucose when needed. Animals store energy as
glycogen (animal starch) and fat.
Two other important organic compounds are fats (lipids) and protein. Carbohydrates do not contain an organic acid. Fats and protein do contain an organic acid. If the carbon backbone of a fat is composed of carbons bonded to each other with single bonds, each carbon can be saturated with hydrogens. This is a saturated fat. If there are some double bonds between the carbons forming the backbone of the fat, the carbons cannot be saturated with hydrogens and it is an unsaturated fat. If there are a lot of these double bonds, it is a polyunsaturated fat. Polyunsaturated fats are better foods than saturated fats.
Proteins are polymers of amino acids. A polymer is a long chain of repeating
units. An amino acid is an organic acid with an amine group. The amine group is
NH2. Therefore, any compound with an organic acid and an amine group is an amino
acid. There are about 20 amino acids. When many amino acids are joined together
they form a protein. Proteins are very important to the structure and functioning
of living things.