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

Vitalism

The name "organic" is historical, dating back to the 1st century.^{[citation needed]} For many centuries, Western alchemists believed in vitalism, the theory that certain compounds could only be synthesized from their classical elements — Earth, Water, Air and Fire — by action of a "life-force" (vis vitalis) possessed only by organisms. The theory implied that these "organic" compounds were fundamentally different from the "inorganic" compounds that could be be obtained from the elements by chemical manipulation.

Vitalism survived for a while even after the rise of modern atomic theory and the replacement of the Aristotelian elements by those we know today. It first came under question in 1824, when Friedrich Wöhler synthesized oxalic acid, a compound known to occur only in living organisms, from cyanogen.^{[citation needed]} A more decisive experiment was Wöhler's 1828 synthesis of urea from the inorganic salts potassium cyanate and ammonium sulfate. Urea had long been considered to be an "organic" compound as it was known to occur only in the urine of living organisms. Wöhler's experiments were followed by many others, where increasingly complex "organic" substances were produced from "inorganic" ones without the involvement of any living organism.^{[citation needed]}

Modern classification

Even after vitalism was disproved, the distinction between "organic" and "inorganic" compounds has been retained to this day but is now merely a tool for organizing the huge and growing body of chemical knowledge — even though many of the "organic compounds" known today have no connection whatsoever, material or structural, to any substance found in living organisms.

Although a perfect definition of "organic compound" is absent, compounds containing C-H bonds are generally recognized as organic, and such compounds are the topic of textbooks on "organic chemistry." Certain compounds lacking C-H bonds are also traditionally included in the scope of the discipline, e.g. benzenehexol, mesoxalic acid, and carbon tetrachloride. Some of these borderline compounds may be covered in "inorganic chemistry" books as well. Curiously, this definition would also exclude oxalic acid and urea — the very biologically-derived "organic" compounds first synthesized by Wöhler.

IUPAC defines "organyl" as "any organic substituent group, regardless of functional type, having one free valence at a carbon atom, e.g. CH₃CH₂–, ClCH₂– , CH₃C(=O)– , 4-pyridylmethyl."^[2] Thus, virtually all of biochemistry and organometallic chemistry can be considered to be a branch of organic chemistry.

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. Organic compounds can also be classified or subdivided by the presence of heteroatoms, e.g. organometallic compounds which feature bonds between carbon and a metal, and organophosphorus compounds which feature bonds between carbon and a phosphorus.

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 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. ^ Spencer L. Seager, Michael R. Slabaugh. Chemistry for Today: general, organic, and biochemistry. Thomson Brooks/Cole, 2004, p. 342. ISBN 053439969X
2. ^ http://goldbook.iupac.org/O04329.html