Organic chemistry is a subdiscipline within
chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
involving the
scientific study of the structure, properties, and reactions of
organic compounds and
organic materials, i.e., matter in its various forms that contain
carbon atoms.
[Clayden, J.; Greeves, N. and Warren, S. (2012) ''Organic Chemistry''. Oxford University Press. pp. 1–15. .] Study of structure determines their
structural formula
The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bondi ...
. Study of properties includes
physical
Physical may refer to:
*Physical examination
In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally co ...
and
chemical properties, and evaluation of
chemical reactivity to understand their behavior. The study of
organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, Mechanistic Organ ...
s includes the
chemical synthesis of
natural product
A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical syn ...
s,
drug
A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via insuffla ...
s, and
polymers, and study of individual organic molecules in the laboratory and via theoretical (
in silico
In biology and other experimental sciences, an ''in silico'' experiment is one performed on computer or via computer simulation. The phrase is pseudo-Latin for 'in silicon' (correct la, in silicio), referring to silicon in computer chips. It ...
) study.
The range of chemicals studied in organic chemistry includes
hydrocarbons (compounds containing only
carbon and
hydrogen) as well as compounds based on carbon, but also containing other elements,
especially
oxygen,
nitrogen,
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
,
phosphorus (included in many
biochemicals
Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...
) and the
halogen
The halogens () are a group in the periodic table consisting of five or six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). In the modern IUPAC nomenclature, this group is ...
s.
Organometallic chemistry
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
is the study of compounds containing carbon–
metal bonds.
In addition, contemporary research focuses on organic chemistry involving other
organometallic
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
s including the
lanthanide
The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttr ...
s, but especially the
transition metals zinc, copper, palladium, nickel, cobalt, titanium and chromium.
Organic compounds form the basis of all
earthly life and constitute the majority of known chemicals. The bonding patterns of carbon, with its
valence
Valence or valency may refer to:
Science
* Valence (chemistry), a measure of an element's combining power with other atoms
* Degree (graph theory), also called the valency of a vertex in graph theory
* Valency (linguistics), aspect of verbs rel ...
of four—formal single, double, and triple bonds, plus structures with delocalized electrons—make the array of organic compounds structurally diverse, and their range of applications enormous. They form the basis of, or are constituents of, many commercial products including
pharmaceuticals
A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and rel ...
;
petrochemicals and
agrichemical
An agrochemical or agrichemical, a contraction of ''agricultural chemical'', is a chemical product used in industrial agriculture. Agrichemical refers to biocides (pesticides including insecticides, herbicides, fungicides and nematicides) and syn ...
s, and products made from them including
lubricants
A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...
,
solvents
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for p ...
;
plastics;
fuels and
explosives
An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...
. The study of organic chemistry overlaps
organometallic chemistry
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
and
biochemistry, but also with
medicinal chemistry,
polymer chemistry, and
materials science.
History
Before the 18th century, chemists generally believed that compounds obtained from living organisms were endowed with a vital force that distinguished them from
inorganic compound
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...
s. According to the concept of
vitalism
Vitalism is a belief that starts from the premise that "living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things." Wher ...
(vital force theory), organic matter was endowed with a "vital force".
During the first half of the nineteenth century, some of the first systematic studies of organic compounds were reported. Around 1816
Michel Chevreul started a study of
soaps made from various
fats and
alkali
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...
s. He separated the acids that, in combination with the alkali, produced the soap. Since these were all individual compounds, he demonstrated that it was possible to make a chemical change in various fats (which traditionally come from organic sources), producing new compounds, without "vital force". In 1828
Friedrich Wöhler
Friedrich Wöhler () FRS(For) HonFRSE (31 July 180023 September 1882) was a German chemist known for his work in inorganic chemistry, being the first to isolate the chemical elements beryllium and yttrium in pure metallic form. He was the firs ...
produced the ''organic'' chemical
urea (carbamide), a constituent of
urine, from ''inorganic'' starting materials (the salts
potassium cyanate and
ammonium sulfate), in what is now called the
Wöhler synthesis. Although Wöhler himself was cautious about claiming he had disproved vitalism, this was the first time a substance thought to be organic was synthesized in the laboratory without biological (organic) starting materials. The event is now generally accepted as indeed disproving the doctrine of vitalism.
In 1856
William Henry Perkin, while trying to manufacture
quinine accidentally produced the organic
dye
A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...
now known as
Perkin's mauve
Mauveine, also known as aniline purple and Perkin's mauve, was one of the first synthetic dyes. It was discovered serendipitously by William Henry Perkin in 1856 while he was attempting to synthesise the phytochemical quinine for the treatment of ...
. His discovery, made widely known through its financial success, greatly increased interest in organic chemistry.
A crucial breakthrough for organic chemistry was the concept of chemical structure, developed independently in 1858 by both
Friedrich August Kekulé and
Archibald Scott Couper.
Both researchers suggested that
tetravalent carbon atoms could link to each other to form a carbon lattice, and that the detailed patterns of atomic bonding could be discerned by skillful interpretations of appropriate chemical reactions.
The era of the
pharmaceutical industry began in the last decade of the 19th century when the German company,
Bayer
Bayer AG (, commonly pronounced ; ) is a German multinational corporation, multinational pharmaceutical and biotechnology company and one of the largest pharmaceutical companies in the world. Headquartered in Leverkusen, Bayer's areas of busi ...
, first manufactured acetylsalicylic acid—more commonly known as
aspirin. By 1910
Paul Ehrlich and his laboratory group began developing arsenic-based
arsphenamine, (Salvarsan), as the first effective medicinal treatment of
syphilis
Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, an ...
, and thereby initiated the medical practice of
chemotherapy. Ehrlich popularized the concepts of "magic bullet" drugs and of systematically improving drug therapies.
His laboratory made decisive contributions to developing antiserum for
diphtheria and standardizing therapeutic serums.

Early examples of organic reactions and applications were often found because of a combination of luck and preparation for unexpected observations. The latter half of the 19th century however witnessed systematic studies of organic compounds. The development of synthetic indigo is illustrative. The production of indigo from plant sources dropped from 19,000 tons in 1897 to 1,000 tons by 1914 thanks to the synthetic methods developed by
Adolf von Baeyer. In 2002, 17,000 tons of synthetic indigo were produced from
petrochemicals.
[Steingruber, Elmar (2004) "Indigo and Indigo Colorants" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim. ]
In the early part of the 20th century,
polymers and
enzymes
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
were shown to be large organic molecules, and petroleum was shown to be of biological origin.
The multiple-step synthesis of complex organic compounds is called total synthesis.
Total synthesis of complex natural compounds increased in complexity to
glucose and
terpineol. For example,
cholesterol-related compounds have opened ways to synthesize complex
human hormones and their modified derivatives. Since the start of the 20th century, complexity of total syntheses has been increased to include molecules of high complexity such as
lysergic acid and
vitamin B12.
left, 230px, The of vitamin B12 marked a major achievement in organic chemistry.">total synthesis of vitamin B
12 marked a major achievement in organic chemistry.
The discovery of
petroleum and the development of the
petrochemical industry spurred the development of organic chemistry. Converting individual petroleum compounds into ''types'' of compounds by various chemical processes led to
organic reactions enabling a broad range of industrial and commercial products including, among (many) others:
plastics
Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics to be Injection moulding, moulded, Extrusion, e ...
,
synthetic rubber
A synthetic rubber is an artificial elastomer. They are polymers synthesized from petroleum byproducts. About 32-million metric tons of rubbers are produced annually in the United States, and of that amount two thirds are synthetic. Synthetic rubbe ...
, organic
adhesives, and various property-modifying petroleum additives and
catalysts.
The majority of chemical compounds occurring in biological organisms are carbon compounds, so the association between organic chemistry and
biochemistry is so close that biochemistry might be regarded as in essence a branch of organic chemistry. Although the
history of biochemistry might be taken to span some four centuries, fundamental understanding of the field only began to develop in the late 19th century and the actual term ''biochemistry'' was coined around the start of 20th century. Research in the field increased throughout the twentieth century, without any indication of slackening in the rate of increase, as may be verified by inspection of abstraction and indexing services such as
BIOSIS Previews and
Biological Abstracts, which began in the 1920s as a single annual volume, but has grown so drastically that by the end of the 20th century it was only available to the everyday user as an online electronic
database.
Characterization
Since organic compounds often exist as
mixture
In chemistry, a mixture is a material made up of two or more different chemical substances which are not chemically bonded. A mixture is the physical combination of two or more substances in which the identities are retained and are mixed in the ...
s, a variety of techniques have also been developed to assess purity;
chromatography techniques are especially important for this application, and include
HPLC
High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify each component in a mixture. It relies on pumps to pa ...
and
gas chromatography
Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substance, ...
. Traditional methods of separation include
distillation,
crystallization
Crystallization is the process by which solid forms, where the atoms or molecules are highly organized into a structure known as a crystal. Some ways by which crystals form are precipitating from a solution, freezing, or more rarely deposi ...
,
evaporation
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...
,
magnetic separation and
solvent extraction.
Organic compounds were traditionally characterized by a variety of chemical tests, called "wet methods", but such tests have been largely displaced by spectroscopic or other computer-intensive methods of analysis. Listed in approximate order of utility, the chief analytical methods are:
*
Nuclear magnetic resonance (NMR) spectroscopy is the most commonly used technique, often permitting the complete assignment of atom connectivity and even stereochemistry using
correlation spectroscopy. The principal constituent atoms of organic chemistry – hydrogen and carbon – exist naturally with NMR-responsive isotopes, respectively
1H and
13C.
*
Elemental analysis: A destructive method used to determine the elemental composition of a molecule. See also mass spectrometry, below.
*
Mass spectrometry
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...
indicates the
molecular weight of a compound and, from the
fragmentation patterns, its structure. High-resolution mass spectrometry can usually identify the exact formula of a compound and is used in place of elemental analysis. In former times, mass spectrometry was restricted to neutral molecules exhibiting some volatility, but advanced ionization techniques allow one to obtain the "mass spec" of virtually any organic compound.
*
Crystallography
Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Crystallography is a fundamental subject in the fields of materials science and solid-state physics (condensed matter physics). The wor ...
can be useful for determining
molecular geometry when a single crystal of the material is available. Highly efficient hardware and software allows a structure to be determined within hours of obtaining a suitable crystal.
Traditional spectroscopic methods such as
infrared spectroscopy,
optical rotation
Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circul ...
, and
UV/VIS spectroscopy provide relatively nonspecific structural information but remain in use for specific applications. Refractive index and density can also be important for substance identification.
Properties
The physical properties of organic compounds typically of interest include both quantitative and qualitative features. Quantitative information includes a melting point, boiling point, solubility, and index of refraction. Qualitative properties include odor, consistency, and color.
Melting and boiling properties
Organic compounds typically melt and many boil. In contrast, while inorganic materials generally can be melted, many do not boil, and instead tend to degrade. In earlier times, the melting point (m.p.) and boiling point (b.p.) provided crucial information on the purity and identity of organic compounds. The melting and boiling points correlate with the polarity of the molecules and their molecular weight. Some organic compounds, especially symmetrical ones,
sublime
Sublime may refer to:
Entertainment
* SuBLime, a comic imprint of Viz Media for BL manga
* Sublime (band), an American ska punk band
** ''Sublime'' (album), 1996
* ''Sublime'' (film), a 2007 horror film
* SubLime FM, a Dutch radio station dedic ...
. A well-known example of a sublimable organic compound is
para-dichlorobenzene
1,4-Dichlorobenzene (1,4-DCB, ''p''-DCB, or ''para''-dichlorobenzene, sometimes abbreviated as PDCB or para) is an organic compound with the formula C6H4Cl2. This colorless solid has a strong odor. The molecule consists of a benzene ring with t ...
, the odiferous constituent of modern mothballs. Organic compounds are usually not very stable at temperatures above 300 °C, although some exceptions exist.
Solubility
Neutral organic compounds tend to be
hydrophobic; that is, they are less
soluble in water than in organic solvents. Exceptions include organic compounds that contain
ionizable
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...
groups as well as low
molecular weight alcohol
Alcohol most commonly refers to:
* Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom
* Alcohol (drug), an intoxicant found in alcoholic drinks
Alcohol may also refer to:
Chemicals
* Ethanol, one of sev ...
s,
amines, and
carboxylic acid
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...
s where
hydrogen bonding occurs. Otherwise, organic compounds tend to dissolve in organic
solvents. Solubility varies widely with the organic solute and with the organic solvent.
Solid state properties
Various specialized properties of
molecular crystals and
organic polymers with
conjugated system
In theoretical chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability. It is conventionally represented as ...
s are of interest depending on applications, e.g. thermo-mechanical and electro-mechanical such as
piezoelectricity, electrical conductivity (see
conductive polymers and
organic semiconductors), and electro-optical (e.g.
non-linear optics) properties. For historical reasons, such properties are mainly the subjects of the areas of
polymer science and
materials science.
Nomenclature
The names of organic compounds are either systematic, following logically from a set of rules, or nonsystematic, following various traditions. Systematic nomenclature is stipulated by specifications from
IUPAC. Systematic nomenclature starts with the name for a
parent structure within the molecule of interest. This parent name is then modified by prefixes, suffixes, and numbers to unambiguously convey the structure. Given that millions of organic compounds are known, rigorous use of systematic names can be cumbersome. Thus, IUPAC recommendations are more closely followed for simple compounds, but not complex molecules. To use the systematic naming, one must know the structures and names of the parent structures. Parent structures include unsubstituted hydrocarbons, heterocycles, and mono functionalized derivatives thereof.
Nonsystematic nomenclature is simpler and unambiguous, at least to organic chemists. Nonsystematic names do not indicate the structure of the compound. They are common for complex molecules, which include most natural products. Thus, the informally named
lysergic acid diethylamide is systematically named
(6a''R'',9''R'')-''N'',''N''-diethyl-7-methyl-4,6,6a,7,8,9-hexahydroindolo-
,3-''fg''quinoline-9-carboxamide.
With the increased use of computing, other naming methods have evolved that are intended to be interpreted by machines. Two popular formats are
SMILES and
InChI.
Structural drawings
Organic molecules are described more commonly by drawings or
structural formula
The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bondi ...
s, combinations of drawings and chemical symbols. The
line-angle formula is simple and unambiguous. In this system, the endpoints and intersections of each line represent one carbon, and hydrogen atoms can either be notated explicitly or assumed to be present as implied by
tetravalent carbon.
History
By 1880 an explosion in the number of chemical compounds being discovered occurred assisted by new synthetic and analytical techniques. Grignard described the situation as "chaos le plus complet" (complete chaos) due to the lack of convention it was possible to have multiple names for the same compound. This led to the creation of the
Geneva rules in 1892.
Classification of organic compounds
Functional groups
The concept of functional groups is central in organic chemistry, both as a means to classify structures and for predicting properties. A functional group is a molecular module, and the reactivity of that functional group is assumed, within limits, to be the same in a variety of molecules. Functional groups can have a decisive influence on the chemical and physical properties of organic compounds. Molecules are classified based on their functional groups. Alcohols, for example, all have the subunit C-O-H. All alcohols tend to be somewhat
hydrophilic, usually form
esters, and usually can be converted to the corresponding
halide
In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a fluor ...
s. Most functional groups feature heteroatoms (atoms other than C and H). Organic compounds are classified according to functional groups, alcohols, carboxylic acids, amines, etc. Functional groups make the molecule more acidic or basic due to their electronic influence on surrounding parts of the molecule.
As the
p''Ka'' (aka
basicity) of the molecular addition/functional group increases, there is a corresponding
dipole, when measured, increases in strength. A dipole directed towards the functional group (higher p''K
a'' therefore basic nature of group) points towards it and decreases in strength with increasing distance. Dipole distance (measured in
Angstroms) and
steric hindrance towards the functional group have an intermolecular and intramolecular effect on the surrounding environment and
pH level.
Different functional groups have different p''K
a'' values and bond strengths (single, double, triple) leading to increased electrophilicity with lower p''K
a'' and increased nucleophile strength with higher p''K
a''. More basic/nucleophilic functional groups desire to attack an electrophilic functional group with a lower p''K
a'' on another molecule (intermolecular) or within the same molecule (intramolecular). Any group with a net acidic p''K
a'' that gets within range, such as an acyl or carbonyl group is fair game. Since the likelihood of being attacked decreases with an increase in p''K
a'',
acyl chloride
In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...
components with the lowest measured
p''Ka'' values are most likely to be attacked, followed by carboxylic acids (p''K
a'' =4), thiols (13), malonates (13), alcohols (17), aldehydes (20), nitriles (25), esters (25), then amines (35). Amines are very basic, and are great nucleophiles/attackers.
Aliphatic compounds
The aliphatic hydrocarbons are subdivided into three groups of
homologous series
In organic chemistry, a homologous series is a sequence of compounds with the same functional group and similar chemical properties in which the members of the series can be branched or unbranched, or differ by molecular formula of and molecu ...
according to their state of
saturation:
* alkanes (paraffins): aliphatic hydrocarbons without any
double or
triple bonds, i.e. just C-C, C-H single bonds
* alkenes (olefins): aliphatic hydrocarbons that contain one or more double bonds, i.e. di-olefins (dienes) or poly-olefins.
* alkynes (acetylenes): aliphatic hydrocarbons which have one or more triple bonds.
The rest of the group is classified according to the functional groups present. Such compounds can be "straight-chain", branched-chain or cyclic. The degree of branching affects characteristics, such as the
octane number
An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without detonating. The higher the octane number, the more compression the fuel can withstand before detonatin ...
or
cetane number in petroleum chemistry.
Both saturated (
alicyclic
In organic chemistry, an alicyclic compound contains one or more all-carbon rings which may be either saturated or unsaturated, but do not have aromatic character. Alicyclic compounds may have one or more aliphatic side chains attached.
The ...
) compounds and unsaturated compounds exist as cyclic derivatives. The most stable rings contain five or six carbon atoms, but large rings (macrocycles) and smaller rings are common. The smallest cycloalkane family is the three-membered
cyclopropane
Cyclopropane is the cycloalkane with the molecular formula (CH2)3, consisting of three methylene groups (CH2) linked to each other to form a ring. The small size of the ring creates substantial ring strain in the structure. Cyclopropane itself ...
((CH
2)
3). Saturated cyclic compounds contain single bonds only, whereas aromatic rings have an alternating (or conjugated) double bond.
Cycloalkane
In organic chemistry, the cycloalkanes (also called naphthenes, but distinct from naphthalene) are the monocyclic saturated hydrocarbons. In other words, a cycloalkane consists only of hydrogen and carbon atoms arranged in a structure containing ...
s do not contain multiple bonds, whereas the
cycloalkenes and the cycloalkynes do.
Aromatic compounds
Aromatic hydrocarbons contain
conjugated double bonds. This means that every carbon atom in the ring is sp2 hybridized, allowing for added stability. The most important example is
benzene, the structure of which was formulated by
Kekulé who first proposed the
delocalization or
resonance principle for explaining its structure. For "conventional" cyclic compounds, aromaticity is conferred by the presence of 4n + 2 delocalized pi electrons, where n is an integer. Particular instability (
antiaromaticity) is conferred by the presence of 4n conjugated pi electrons.
Heterocyclic compounds
The characteristics of the cyclic hydrocarbons are again altered if heteroatoms are present, which can exist as either substituents attached externally to the ring (exocyclic) or as a member of the ring itself (endocyclic). In the case of the latter, the ring is termed a
heterocycle.
Pyridine and
furan
Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen atom. Chemical compounds containing such rings are also referred to as furans.
Furan is a colorless, flammable, highly ...
are examples of aromatic heterocycles while
piperidine and
tetrahydrofuran are the corresponding
alicyclic
In organic chemistry, an alicyclic compound contains one or more all-carbon rings which may be either saturated or unsaturated, but do not have aromatic character. Alicyclic compounds may have one or more aliphatic side chains attached.
The ...
heterocycles. The heteroatom of heterocyclic molecules is generally oxygen, sulfur, or nitrogen, with the latter being particularly common in biochemical systems.
Heterocycles are commonly found in a wide range of products including aniline dyes and medicines. Additionally, they are prevalent in a wide range of biochemical compounds such as
alkaloids
Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar st ...
, vitamins, steroids, and nucleic acids (e.g. DNA, RNA).
Rings can fuse with other rings on an edge to give
polycyclic compounds. The
purine nucleoside bases are notable polycyclic aromatic heterocycles. Rings can also fuse on a "corner" such that one atom (almost always carbon) has two bonds going to one ring and two to another. Such compounds are termed
spiro and are important in several
natural product
A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical syn ...
s.
Polymers
One important property of carbon is that it readily forms chains, or networks, that are linked by carbon-carbon (carbon-to-carbon) bonds. The linking process is called
polymerization, while the chains, or networks, are called
polymers. The source compound is called a
monomer.
Two main groups of polymers exist
synthetic polymers
Some familiar household synthetic polymers include: Nylons in textiles and fabrics, Teflon in non-stick pans, Bakelite for electrical switches, polyvinyl chloride (PVC) in pipes, etc. The common PET bottles are made of a synthetic polymer, polye ...
and
biopolymer
Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, cl ...
s. Synthetic polymers are artificially manufactured, and are commonly referred to as
industrial polymers.
["industrial polymers, chemistry of." Encyclopædia Britannica. 2006] Biopolymers occur within a respectfully natural environment, or without human intervention.
Biomolecules
Biomolecular chemistry is a major category within organic chemistry which is frequently studied by
biochemists. Many complex multi-functional group molecules are important in living organisms. Some are long-chain
biopolymer
Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, cl ...
s, and these include
peptides
Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides.
A p ...
,
DNA,
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
and the
polysaccharide
Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wa ...
s such as
starch
Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...
es in animals and
celluloses in plants. The other main classes are
amino acids (monomer building blocks of peptides and proteins),
carbohydrates (which includes the polysaccharides), the
nucleic acid
Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main cl ...
s (which include DNA and RNA as polymers), and the
lipids. Besides, animal biochemistry contains many small molecule intermediates which assist in energy production through the
Krebs cycle, and produces
isoprene
Isoprene, or 2-methyl-1,3-butadiene, is a common volatile organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. Isoprene is an unsaturated hydrocarbon. It is produced by many plants and animals ...
, the most common hydrocarbon in animals. Isoprenes in animals form the important
steroid
A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and a ...
structural (
cholesterol) and steroid hormone compounds; and in plants form
terpenes,
terpenoids, some
alkaloids, and a class of hydrocarbons called biopolymer polyisoprenoids present in the
latex of various species of plants, which is the basis for making
rubber.
See also:
peptide synthesis,
oligonucleotide synthesis and
carbohydrate synthesis
Carbohydrate synthesis is a sub-field of organic chemistry concerned specifically with the generation of natural and unnatural carbohydrate structures. This can include the synthesis of monosaccharide residues or structures containing more than on ...
.
Small molecules

In pharmacology, an important group of organic compounds is
small molecules, also referred to as 'small organic compounds'. In this context, a small molecule is a small organic compound that is biologically active but is not a
polymer. In practice, small molecules have a
molar mass less than approximately 1000 g/mol.
Fullerenes
Fullerenes and
carbon nanotube
A scanning tunneling microscopy image of a single-walled carbon nanotube
Rotating single-walled zigzag carbon nanotube
A carbon nanotube (CNT) is a tube made of carbon with diameters typically measured in nanometers.
''Single-wall carbon na ...
s, carbon compounds with spheroidal and tubular structures, have stimulated much research into the related field of
materials science. The first fullerene was discovered in 1985 by Sir Harold W. Kroto of the United Kingdom and by Richard E. Smalley and Robert F. Curl, Jr., of the United States. Using a laser to vaporize graphite rods in an atmosphere of helium gas, these chemists and their assistants obtained cagelike molecules composed of 60 carbon atoms (C60) joined by single and double bonds to form a hollow sphere with 12 pentagonal and 20 hexagonal faces—a design that resembles a football, or soccer ball. In 1996 the trio was awarded the Nobel Prize for their pioneering efforts. The C60 molecule was named
buckminsterfullerene (or, more simply, the buckyball) after the American architect R. Buckminster Fuller, whose geodesic dome is constructed on the same structural principles.
Others
Organic compounds containing bonds of carbon to nitrogen, oxygen and the halogens are not normally grouped separately. Others are sometimes put into major groups within organic chemistry and discussed under titles such as
organosulfur chemistry,
organometallic chemistry
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
,
organophosphorus chemistry and
organosilicon chemistry.
Organic reactions
Organic reaction
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, Mechanistic Organ ...
s are
chemical reactions involving
organic compounds. Many of these reactions are associated with functional groups. The general theory of these reactions involves careful analysis of such properties as the
electron affinity of key atoms,
bond strengths and
steric hindrance. These factors can determine the relative stability of short-lived
reactive intermediate
In chemistry, a reactive intermediate or an intermediate is a short-lived, high-energy, highly reactive molecule. When generated in a chemical reaction, it will quickly convert into a more stable molecule. Only in exceptional cases can these comp ...
s, which usually directly determine the path of the reaction.
The basic reaction types are:
addition reactions,
elimination reactions,
substitution reactions
A substitution reaction (also known as single displacement reaction or single substitution reaction) is a chemical reaction during which one functional group in a chemical compound is replaced by another functional group. Substitution reactions ar ...
,
pericyclic reactions, rearrangement reactions and
redox reactions
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
. An example of a common reaction is a
substitution reaction written as:
:
Nu- + C-X -> C-Nu + X-
where X is some
functional group and Nu is a
nucleophile
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...
.
The number of possible organic reactions is infinite. However, certain general patterns are observed that can be used to describe many common or useful reactions. Each reaction has a stepwise reaction mechanism that explains how it happens in sequence—although the detailed description of steps is not always clear from a list of reactants alone.
The stepwise course of any given reaction mechanism can be represented using
arrow pushing techniques in which curved arrows are used to track the movement of electrons as starting materials transition through intermediates to final products.
Organic synthesis
Synthetic organic chemistry is an
applied science
Applied science is the use of the scientific method and knowledge obtained via conclusions from the method to attain practical goals. It includes a broad range of disciplines such as engineering and medicine. Applied science is often contrasted ...
as it borders
engineering, the "design, analysis, and/or construction of works for practical purposes". Organic synthesis of a novel compound is a problem-solving task, where a synthesis is designed for a target molecule by selecting optimal reactions from optimal starting materials. Complex compounds can have tens of reaction steps that sequentially build the desired molecule. The synthesis proceeds by utilizing the reactivity of the functional groups in the molecule. For example, a
carbonyl compound can be used as a
nucleophile
In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...
by converting it into an
enolate, or as an
electrophile; the combination of the two is called the
aldol reaction. Designing practically useful syntheses always requires conducting the actual synthesis in the laboratory. The scientific practice of creating novel synthetic routes for complex molecules is called
total synthesis.
Strategies to design a synthesis include
retrosynthesis
Retrosynthetic analysis is a technique for solving problems in the planning of organic syntheses. This is achieved by transforming a target molecule into simpler precursor structures regardless of any potential reactivity/interaction with reagents. ...
, popularized by
E.J. Corey
Elias James Corey (born July 12, 1928) is an American organic chemist. In 1990, he won the Nobel Prize in Chemistry "for his development of the theory and methodology of organic synthesis", specifically retrosynthetic analysis. Regarded by many ...
, which starts with the target molecule and splices it to pieces according to known reactions. The pieces, or the proposed precursors, receive the same treatment, until available and ideally inexpensive starting materials are reached. Then, the retrosynthesis is written in the opposite direction to give the synthesis. A "synthetic tree" can be constructed because each compound and also each precursor has multiple syntheses.
See also
*
Important publications in organic chemistry
*
List of organic reactions
*
Molecular modelling
References
External links
MIT.edu OpenCourseWare: Organic Chemistry I
HaverFord.edu Organic Chemistry Lectures, Videos and Text
Organic-Chemistry.org Organic Chemistry Portal – Recent Abstracts and (Name)Reactions
Orgsyn.org Organic Chemistry synthesis journal
Clutchprep.com Organic Chemistry Video Lectures and Practice Problems
Khanacademy.org Khan Academy - Organic Chemistry
{{DEFAULTSORT:Organic Chemistry
Chemistry
Chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...