Organic compound

Organic compounds are a specific subclass of chemical compounds defined by their relationship to carbon. While chemists do not have one single, perfect definition, most agree that organic compounds are the primary subject of organic chemistry. Generally, a compound is considered organic if it contains carbon–hydrogen or carbon–carbon bonds. This includes alkanes, such as ethane, and many of their derivatives.

Because carbon has the unique ability to catenate, it can form long chains with other carbon atoms. This ability allows for the existence of millions of different organic compounds.

Defining the exact boundary between organic and inorganic chemistry can be difficult. For historical reasons, several carbon-containing substances are classified as inorganic. These include simple oxides of carbon like carbon dioxide, as well as carbonates and cyanides. Even some carbon-containing alloys, such as steel, are considered inorganic. Other exceptions include carbides and the allotropes of pure carbon, such as diamond and graphite. Because these are simple substances made of only one element, they are not usually called chemical compounds.

In the past, scientists followed a theory known as vitalism. This was the belief that organic substances were created by a "vital force" or "life-force" found only in living organisms. In the 1810s, Jöns Jacob Berzelius argued that organic compounds required living bodies for their synthesis. He believed that inorganic compounds could be made through chemical manipulation in a lab, but organic ones could not. This distinction kept the two fields strictly separate in the minds of early scientists.

This view changed through the work of Friedrich Wöhler in the 1820s. In 1824, Wöhler successfully synthesized oxalic acid from cyanogen, a non-living source. A few years later, in 1828, he performed an even more famous experiment. He synthesized urea from the inorganic salts potassium cyanate and ammonium sulfate. Since urea was known to occur in the urine of living things, this proved that organic molecules could be made without a life-force. This discovery helped disprove vitalism and expanded the scope of organic chemistry.

Today, organic compounds are categorized in several ways. One major division is between natural products and synthetic compounds. Natural products are molecules produced by plants or animals, such as vitamins, fats, and proteins. Many are still extracted from nature because they are too complex to make easily in a lab. Synthetic compounds are those prepared by reacting other chemicals. This category includes most polymers, such as the plastics and rubbers used in everyday life.

Another way to classify these molecules is by their structure and composition. Some organic compounds are small molecules, while others are large polymers. Scientists also look for heteroatoms, which are atoms other than carbon or hydrogen. For example, organometallic compounds feature bonds between carbon and a metal. There are also organophosphorus compounds, which contain phosphorus. In biotechnology, scientists use organisms like bacteria or yeast to manufacture compounds like insulin. They often alter the DNA of these organisms to produce specific organic molecules.

Organic chemistry is also deeply connected to the Earth's systems. All known life is based on organic compounds. Living things use the carbon cycle to turn carbon dioxide and water into simple sugars. These sugars then become the building blocks for other organic molecules. In industry, many synthetic organic compounds come from petrochemicals. These are formed from biological matter that has degraded underground under high pressure and temperature. This links the ancient history of life to the modern chemical industry.