Organic chemistry is a subdiscipline within
chemistry involving the
scientific
Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe.
Science may be as old as the human species, and some of the earliest archeological evidence for ...
study of the structure, properties, and reactions of
organic compounds
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The s ...
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. Study of properties includes
physical and
chemical properties
A chemical property is any of a material's properties that becomes evident during, or after, a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity.William L. Masterton, Cecile N. Hurley, ...
, and evaluation of
chemical reactivity
In chemistry, reactivity is the impulse for which a chemical substance undergoes a chemical reaction, either by itself or with other materials, with an overall release of energy.
''Reactivity'' refers to:
* the chemical reactions of a single su ...
to understand their behavior. The study of
organic reactions includes the
chemical synthesis of
natural products,
drugs, and
polymers, and study of individual organic molecules in the laboratory and via theoretical (
in silico) study.
The range of chemicals studied in organic chemistry includes
hydrocarbons (compounds containing only
carbon and
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
) as well as compounds based on carbon, but also containing other elements,
especially
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...
,
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
,
sulfur,
phosphorus (included in many
biochemicals) and the
halogens.
Organometallic chemistry is the study of compounds containing carbon–
metal bonds.
In addition, contemporary research focuses on organic chemistry involving other
organometallics including the
lanthanides, 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 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;
petrochemicals and
agrichemicals, and products made from them including
lubricants,
solvents;
plastics;
fuels
A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...
and
explosives. The study of organic chemistry overlaps
organometallic chemistry and
biochemistry, but also with
medicinal chemistry
Medicinal or pharmaceutical chemistry is a scientific discipline at the intersection of chemistry and pharmacy involved with designing and developing pharmaceutical drugs. Medicinal chemistry involves the identification, synthesis and developme ...
,
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 compounds. According to the concept of
vitalism (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
fat
In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food.
The term often refers specifically to triglycerides (triple est ...
s and
alkalis. 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 produced the ''organic'' chemical
urea (carbamide), a constituent of
urine, from ''inorganic'' starting materials (the salts
potassium cyanate and
ammonium sulfate
Ammonium sulfate (American English and international scientific usage; ammonium sulphate in British English); (NH4)2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen a ...
), in what is now called the
Wöhler synthesis
The Wöhler synthesis is the conversion of ammonium cyanate into urea. This chemical reaction was described in 1828 by Friedrich Wöhler. It is often cited as the starting point of modern organic chemistry. Although the Wöhler reaction concerns ...
. 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 now known as
Perkin's mauve. 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
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules.
Description
The combining capacity, or affinity of an ...
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, first manufactured acetylsalicylic acid—more commonly known as
aspirin. By 1910
Paul Ehrlich
Paul Ehrlich (; 14 March 1854 – 20 August 1915) was a Nobel Prize-winning German physician and scientist who worked in the fields of hematology, immunology, and antimicrobial chemotherapy. Among his foremost achievements were finding a cure ...
and his laboratory group began developing arsenic-based
arsphenamine
Arsphenamine, also known as Salvarsan or compound 606, is a drug that was introduced at the beginning of the 1910s as the first effective treatment for syphilis, relapsing fever, and African trypanosomiasis.
This organoarsenic compound was the f ...
, (Salvarsan), as the first effective medicinal treatment of
syphilis, and thereby initiated the medical practice of
chemotherapy
Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...
. 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 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
Total synthesis is the complete chemical synthesis of a complex molecule, often a natural product, from simple, commercially-available precursors. It usually refers to a process not involving the aid of biological processes, which distinguishes i ...
of complex natural compounds increased in complexity to
glucose and
terpineol. For example,
cholesterol-related compounds have opened ways to synthesize complex
human hormones
The following is a list of hormones found in ''Homo sapiens''. Spelling is not uniform for many hormones. For example, current North American and international usage uses estrogen
Estrogen or oestrogen is a category of sex hormone responsibl ...
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,
synthetic rubber, organic
adhesives
Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation.
The use of adhesives offers certain advant ...
, and various property-modifying petroleum additives and
catalysts
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
.
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
mixtures, a variety of techniques have also been developed to assess purity;
chromatography
In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system ( ...
techniques are especially important for this application, and include
HPLC and
gas chromatography. Traditional methods of separation include
distillation,
crystallization,
evaporation,
magnetic separation
Magnetic separation is the process of separating components of mixtures by using a magnet to attract magnetic substances. The process that is used for magnetic separation separates non-magnetic substances from those which are magnetic. This techniq ...
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
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fie ...
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 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 can be useful for determining
molecular geometry
Molecular geometry is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that dete ...
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, 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. A well-known example of a sublimable organic compound is
para-dichlorobenzene, 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 chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution.
The extent of the solubi ...
in water than in organic solvents. Exceptions include organic compounds that contain
ionizable groups as well as low
molecular weight alcohols,
amine
In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen
Hydrogen is the chemical element wi ...
s, and
carboxylic acids where
hydrogen bonding
In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a l ...
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 systems are of interest depending on applications, e.g. thermo-mechanical and electro-mechanical such as
piezoelectricity, electrical conductivity (see
conductive polymer
Conductive polymers or, more precisely, intrinsically conducting polymers (ICPs) are organic polymers that conduct electricity. Such compounds may have metallic conductivity or can be semiconductors. The biggest advantage of conductive polymers ...
s and
organic semiconductor
Organic semiconductors are solids whose building blocks are pi-bonded molecules or polymers made up by carbon and hydrogen atoms and – at times – heteroatoms such as nitrogen, sulfur and oxygen. They exist in the form of molecular crystals or ...
s), and electro-optical (e.g.
non-linear optics
Nonlinear optics (NLO) is the branch of optics that describes the behaviour of light in ''nonlinear media'', that is, media in which the polarization density P responds non-linearly to the electric field E of the light. The non-linearity is typica ...
) properties. For historical reasons, such properties are mainly the subjects of the areas of
polymer science
Polymer science or macromolecular science is a subfield of materials science concerned with polymers, primarily synthetic polymers such as plastics and elastomers. The field of polymer science includes researchers in multiple disciplines includ ...
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
In chemistry, a parent structure is the structure of an unadorned ion or molecule from which derivatives can be visualized. Parent structures underpin systematic nomenclature and facilitate classification. Fundamental parent structures have one ...
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
Lysergic acid diethylamide (LSD), also known colloquially as acid, is a potent psychedelic drug. Effects typically include intensified thoughts, emotions, and sensory perception. At sufficiently high dosages LSD manifests primarily mental, vi ...
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 formulas, 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
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with other atoms when it forms chemical compounds or molecules.
Description
The combining capacity, or affinity of an ...
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
A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press.
In contrast, hydrophobes are ...
, usually form
esters, and usually can be converted to the corresponding
halides. 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
In physics, a dipole () is an electromagnetic phenomenon which occurs in two ways:
*An electric dipole deals with the separation of the positive and negative electric charges found in any electromagnetic system. A simple example of this system ...
, 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
The angstromEntry "angstrom" in the Oxford online dictionary. Retrieved on 2019-03-02 from https://en.oxforddictionaries.com/definition/angstrom.Entry "angstrom" in the Merriam-Webster online dictionary. Retrieved on 2019-03-02 from https://www.m ...
) and
steric hindrance
Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivity of ions ...
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 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 according to their state of
saturation
Saturation, saturated, unsaturation or unsaturated may refer to:
Chemistry
* Saturation, a property of organic compounds referring to carbon-carbon bonds
**Saturated and unsaturated compounds
** Degree of unsaturation
**Saturated fat or fatty aci ...
:
* 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 or
cetane number
Cetane number (cetane rating) is an indicator of the combustion speed of diesel fuel and compression needed for ignition. It plays a similar role for diesel as octane rating does for gasoline. The CN is an important factor in determining the quali ...
in petroleum chemistry.
Both saturated (
alicyclic) 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 ((CH
2)
3). Saturated cyclic compounds contain single bonds only, whereas aromatic rings have an alternating (or conjugated) double bond.
Cycloalkanes 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
In chemistry, delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond.IUPAC Gold Boo''delocalization''/ref>
The term delocalization is general and can have slightly dif ...
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
Antiaromaticity is a chemical property of a cyclic molecule with a π electron system that has higher energy, i.e., it is less stable due to the presence of 4n delocalised (π or lone pair) electrons in it, as opposed to aromaticity. Unlike aroma ...
) 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
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...
.
Pyridine and
furan are examples of aromatic heterocycles while
piperidine
Piperidine is an organic compound with the molecular formula (CH2)5NH. This heterocyclic amine consists of a six-membered ring containing five methylene bridges (–CH2–) and one amine bridge (–NH–). It is a colorless liquid with an odor de ...
and
tetrahydrofuran are the corresponding
alicyclic 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, vitamins, steroids, and nucleic acids (e.g. DNA, RNA).
Rings can fuse with other rings on an edge to give
polycyclic compound
In the field of organic chemistry, a polycyclic compound is an organic compound featuring several closed rings of atoms, primarily carbon. These ring substructures include cycloalkanes, aromatics, and other ring types. They come in sizes of ...
s. 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 products.
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 and
biopolymers. 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
Biochemists are scientists who are trained in biochemistry. They study chemical processes and chemical transformations in living organisms. Biochemists study DNA, proteins and Cell (biology), cell parts. The word "biochemist" is a portmanteau of ...
. Many complex multi-functional group molecules are important in living organisms. Some are long-chain
biopolymers, and these include
peptides,
DNA,
RNA and the
polysaccharides such as
starches in animals and
cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...
s in plants. The other main classes are
amino acids (monomer building blocks of peptides and proteins),
carbohydrates (which includes the polysaccharides), the
nucleic acids (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
The citric acid cycle (CAC)—also known as the Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and protein ...
, and produces
isoprene, the most common hydrocarbon in animals. Isoprenes in animals form the important
steroid structural (
cholesterol) and steroid hormone compounds; and in plants form
terpenes,
terpenoid
The terpenoids, also known as isoprenoids, are a class of naturally occurring organic chemicals derived from the 5-carbon compound isoprene and its derivatives called terpenes, diterpenes, etc. While sometimes used interchangeably with "terpenes" ...
s, 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
In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl ...
,
oligonucleotide synthesis and
carbohydrate synthesis.
Small molecules
In pharmacology, an important group of organic compounds is
small molecule
Within the fields of molecular biology and pharmacology, a small molecule or micromolecule is a low molecular weight (≤ 1000 daltons) organic compound that may regulate a biological process, with a size on the order of 1 nm. Many drugs ...
s, 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
In chemistry, the molar mass of a chemical compound is defined as the mass of a sample of that compound divided by the amount of substance which is the number of moles in that sample, measured in moles. The molar mass is a bulk, not molecular, ...
less than approximately 1000 g/mol.
Fullerenes
Fullerene
A fullerene is an allotrope of carbon whose molecule consists of carbon atoms connected by single and double bonds so as to form a closed or partially closed mesh, with fused rings of five to seven atoms. The molecule may be a hollow sphere, ...
s and
carbon nanotubes, 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
Buckminsterfullerene is a type of fullerene with the formula C60. It has a cage-like fused-ring structure (truncated icosahedron) made of twenty hexagons and twelve pentagons, and resembles a soccer ball. Each of its 60 carbon atoms is bonded ...
(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
Organosulfur compounds are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature abounds with organosulfur compounds—sulfur ...
,
organometallic chemistry,
organophosphorus chemistry
Organophosphorus compounds are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective in ...
and
organosilicon chemistry
Organosilicon compounds are organometallic compounds containing carbon–silicon bonds. Organosilicon chemistry is the corresponding science of their preparation and properties. Most organosilicon compounds are similar to the ordinary organic c ...
.
Organic reactions
Organic reactions 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 strength
In chemistry, bond energy (''BE''), also called the mean bond enthalpy or average bond enthalpy is the measure of bond strength in a chemical bond. IUPAC defines bond energy as the average value of the gas-phase bond-dissociation energy (usually at ...
s and
steric hindrance
Steric effects arise from the spatial arrangement of atoms. When atoms come close together there is a rise in the energy of the molecule. Steric effects are nonbonding interactions that influence the shape ( conformation) and reactivity of ions ...
. These factors can determine the relative stability of short-lived
reactive intermediates, which usually directly determine the path of the reaction.
The basic reaction types are:
addition reactions
Addition (usually signified by the plus symbol ) is one of the four basic operations of arithmetic, the other three being subtraction, multiplication and division. The addition of two whole numbers results in the total amount or '' sum'' of ...
,
elimination reactions,
substitution reactions,
pericyclic reactions, rearrangement reactions and
redox reactions. An example of a common reaction is a
substitution reaction
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 ...
written as:
:
Nu- + C-X -> C-Nu + X-
where X is some
functional group and Nu is a
nucleophile.
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 Arrow pushing or electron pushing is a technique used to describe the progression of organic chemistry reaction mechanisms. It was first developed by Sir Robert Robinson. In using arrow pushing, "curved arrows" or "curly arrows" are drawn on the ...
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 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
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containi ...
compound can be used as a
nucleophile by converting it into an
enolate
In organic chemistry, enolates are organic anions derived from the deprotonation of carbonyl () compounds. Rarely isolated, they are widely used as reagents in the synthesis of organic compounds.
Bonding and structure
Enolate anions are electr ...
, or as an
electrophile
In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carrie ...
; 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
Total synthesis is the complete chemical synthesis of a complex molecule, often a natural product, from simple, commercially-available precursors. It usually refers to a process not involving the aid of biological processes, which distinguishes i ...
.
Strategies to design a synthesis include
retrosynthesis, popularized by
E.J. Corey, 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
Molecular modelling encompasses all methods, theoretical and computational, used to model or mimic the behaviour of molecules. The methods are used in the fields of computational chemistry, drug design, computational biology and materials sci ...
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