Organic compound

Methane is one of the simplest organic compounds

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic. The division between "organic" and "inorganic" carbon compounds while "useful in organizing the vast subject of chemistry...is somewhat arbitrary".^[1]

Organic chemistry is the science concerned with all aspects of organic compounds. Organic synthesis is the methodology of their preparation.

History

The name "organic" is historical, dating back to the 1st century, when it was believed that organic compounds could only be synthesized in dead organisms through vis vitalis—the "life-force". Vitalism, the theory that organic compounds were fundamentally different from those that were "inorganic", that is, not synthesized through a life-force, came under question in 1824 when Friedrich Wöhler synthesized oxalic acid, a known compound made by living organisms, from cyanogen. A more famous experiment of 1828 involved the synthesis of urea by Wöhler in the Wöhler synthesis. Urea was well-known as an "organic" compound by definition of its known occurrence only in the urine of living organisms, but Wöhler produced urea from the inorganic salts potassium cyanate and ammonium sulfate, without the action of a living organism.

Notably, neither oxalic acid nor urea itself, the two historical prototypical organic compounds made by Wöhler, contain a C–H bond, even though this criterion has sometimes been used as a chemical definition of organic compounds. This may serve to illustrate the residual imperfect match which still exists between historical and attempted chemical definitions of terms. However, the kinds of carbon compounds that are still traditionally considered inorganic are those that were considered inorganic before Wöhler's time; that is, those which came from "inorganic" (i.e., lifeless) sources such as certain carbonate minerals.^[1] However, the mineral "coal," which is derived from plants, is usually considered to be organic under this loose historical definition (as would other so-called fossil fuels). Such a definition, however, would not include the mineral diamond.

Classification

See Organic chemistry#Classification of organic substances

Organic compounds may be classified in a variety of ways. One major distinction is between natural and synthetic compounds. They may also be distinguished by the presence of additional atoms of further elements, so-called heteroatoms. Organometallic compounds constitute a further subsection, characterized by covalent bonds between organic carbon and a metal.

There is also a large number of inorganic carbon compounds to distinguish from organic compounds.

Another distinction, based upon the size of organic compounds, distinguishes between small molecules and polymers.

Natural compounds

Natural compounds refer to those that are produced by plants or animals. Many of these are still extracted from natural sources because they would be far too expensive to be produced artificially. Examples include most sugars, some alkaloids and terpenoids, certain nutrients such as vitamin B₁₂, and in general, those natural products with large or stereoisometrically complicated molecules which are present in reasonable concentrations in living organisms.

Further compounds of prime importance in biochemistry are antigens, carbohydrates, enzymes, hormones, lipids and fatty acids, neurotransmitters, nucleic acids, proteins, peptides and amino acids, vitamins and fats and oils.

Synthetic compounds

Compounds that are prepared by reaction of other compounds are referred to as "synthetic". They may be either compounds that already are found in plants or animals, or those that do not occur naturally.

Many polymers, including all plastics, are organic compounds.

Nomenclature

The IUPAC nomenclature of organic compounds slightly differs from the CAS nomenclature.

Databases

• The CAS database is the most comprehensive repository for data on organic compounds. The search tool SciFinder is offered.

• The Beilstein database contains information on 9.8 million substances, covers the scientific literature from 1771 to the present, and is today accessible via CrossFire. Structures and a large diversity of physical and chemical properties is available for each substance, with reference to original literature.

• PubChem contains 18.4 million entries on compounds and especially covers the field of medicinal chemistry.

There is a great number of more specialized databases for diverse branches of organic chemistry.

Structure determination

See Structure determination

Today, the main tools are proton and carbon-13 NMR spectroscopy and X-ray crystallography.

See also

• Organometallic compounds
• List of organic compounds | List of chemical compounds
• Inorganic compounds

References

1. ^ ^{a b} Spencer L. Seager, Michael R. Slabaugh. Chemistry for Today: general, organic, and biochemistry. Thomson Brooks/Cole, 2004, p. 342. ISBN 053439969X