Until 1828, chemists divided compounds into compounds that chemists could produce and compounds that only organisms could produce. The compounds produced by organisms were called organic compounds. In 1828, a German chemist, Friedrich Wöhler, mixed silver cyanate, AgOCN, with ammonium chloride, NH₄Cl. He expected to make ammonium cyanate. Instead, he produced urea, (NH₂)₂CO, which is a product of reactions that occur in the livers of many organisms. Wöhler had synthesized an organic compound.

Figure 1  A whale's survival depends on carbon compounds. Carbon compounds form the structures of a whale's cells and control reactions that take place in those cells. The instructions for these processes are stored in organic compounds.

An organic compound contains carbon and hydrogen, often combined with a few other elements such as oxygen and nitrogen. There are millions of organic compounds—more than 90 percent of all known compounds. Remember that carbon has four valence electrons. So a carbon atom can form four single covalent bonds, or a double bond and two single bonds, or a triple bond and a single bond. Most of the bonds in organic compounds are carbon-to-carbon bonds or carbon-to-hydrogen bonds.