An organic compound is any member of a large class of gaseous, liquid, or solid chemical
compounds whose molecules contain carbon.
For historical reasons discussed below, a few types of carbon-containing compounds such
as carbides, carbonates, simple oxides of carbon, and cyanides are considered inorganic.
The distinction between organic and inorganic carbon compounds, while "useful in organizing
the vast subject of chemistry... is somewhat arbitrary."
Organic chemistry is the science concerned with all aspects of organic compounds.
Organic synthesis is the methodology of their preparation.
History Vitalism
The word organic is historical, dating to the 1st century.
For many centuries, Western alchemists believed in vitalism.
This is the theory that certain compounds could be synthesized only from their classical
elements—earth, water, air, and fire—by the action of a "life-force" that only organisms
possessed.
Vitalism taught that these "organic" compounds were fundamentally different from the "inorganic"
compounds that could 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.
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 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.
Modern classification Even though vitalism has been discredited,
scientific nomenclature retains the distinction between organic and inorganic compounds.
The modern meaning of organic compound is any compound that contains a significant amount
of carbon—even though many of the organic compounds known today have no connection to
any substance found in living organisms.
There is no single "official" definition of an organic compound.
Some textbooks define an organic compound as one that contains one or more C-H bonds.
Others include C-C bonds in the definition.
Others state that if a molecule contains carbon―it is organic.
Even the broader definition of "carbon-containing molecules" requires the exclusion of carbon-containing
alloys, a relatively small number of carbon-containing compounds such as metal carbonates and carbonyls,
simple oxides of carbon and cyanides, as well as the allotropes of carbon and simple carbon
halides and sulfides, which are usually considered inorganic.
The "C-H" definition excludes compounds that are historically and practically considered
organic.
Neither urea nor oxalic acid is organic by this definition, yet they were two key compounds
in the vitalism debate.
The IUPAC Blue Book on organic nomenclature specifically mentions urea and oxalic acid.
Other compounds lacking C-H bonds that are also traditionally considered organic include
benzenehexol, mesoxalic acid, and carbon tetrachloride.
Mellitic acid, which contains no C-H bonds, is considered a possible organic substance
in Martian soil.
C-C bond is found in most organic compounds, except some small molecules like methane and
methanol, which have only one carbon atom in their structure.
The "C-H bond-only" rule also leads to somewhat arbitrary divisions in sets of carbon-fluorine
compounds, as, for example, Teflon is considered by this rule "inorganic" but Tefzel organic.
Likewise, many Halons are considered inorganic, whereas the rest are considered organic.
For these and other reasons, most sources believe C-H compounds are only a subset of
"organic" compounds.
In summary, most carbon-containing compounds are organic, and almost all organic compounds
contain at least a C-H bond or a C-C bond.
A compound does not need to contain C-H bonds to be considered organic, but many organic
compounds do.
Classification
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.
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 more expensive
to produce 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, lectins, 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.
Most polymers, are organic synthetic or semi-synthetic compounds.
Biotechnology Several compounds are industrially manufactured
utilizing the biochemistry of organisms such as bacteria and yeast.
Two examples are ethanol and insulin.
Regularly the DNA of the organism is altered to express desired compounds, often not ordinarily
produced by that organism.
Sometimes the biotechnologically engineered compounds were never present in nature in
the first place.
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 Reaxys.
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 Inorganic compounds
List of chemical compounds List of organic compounds
Organometallic compounds References
External links Organic Compounds Database