A carbanion is an anion in which carbon has an unshared pair of electrons and bears a negative charge usually with three substituents for a total of eight valence electrons ^[1]. The carbanion exists in a trigonal pyramidal geometry. Formally a carbanion is the conjugate base of a carbon acid. An anion is an ion with negative charge. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Standard atomic weight 12. ... e- redirects here. ... In chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base. ... In the field of chemistry, in the Brønsted-Lowry (protonic) theory of acids and bases, a conjugate base is the basic member, X-, of a pair of compounds that differ only by the presence or absence of a proton at a certain position. ...

R₃C-H + B⁻ → R₃C⁻ + H-B

where B stands for the base. A carbanion is one of several reactive intermediates in organic chemistry. In chemistry a reactive intermediate is a short-lived high energy highly reactive molecule. ... Organic chemistry is a specific discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of chemical compounds consisting of primarily carbon and hydrogen, which may contain any number of other elements, including nitrogen, oxygen, halogens as well...

Theory

A carbanion is a nucleophile. The stability and reactivity of a carbanion is determined by several factors. These include In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ...

1. The inductive effect. Electronegative atoms adjacent to the charge will stabilize the charge;
2. Hybridisation of the charge-bearing atom. The greater the s-character of the charge-bearing atom, the more stable the anion;
3. The extent of conjugation of the anion. Resonance effects can stabilise the anion. This is especially true when the anion is stabilized as a result of aromaticity.

A carbanion is a reactive intermediate and is encountered in organic chemistry for instance in the E1cB elimination reaction and in organometallic chemistry in for instance a Grignard reaction or in alkyl lithium chemistry. Stable carbanions do however exist. In 1984 Olmstead presented the lithium crown ether salt of the diphenylmethyl carbanion from diphenylmethane, butyl lithium and 12-crown-4 at low temperatures^[2]: The inductive effect is associated with the dipole moment of the compound R-X. If X is at the negative end of a dipole moment, it will draw electrons from the ring and produce -I effect. ... In genetics, hybridisation is the process of mixing different species or varieties of organisms. ... A chemically conjugated system, is a system of atoms covalently bonded with alternating single and double bonds (e. ... Resonance in chemistry is a tool used to represent and model certain types of non-classical molecular structures. ... Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. ... In chemistry a reactive intermediate is a short-lived high energy highly reactive molecule. ... Organic chemistry is a specific discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of chemical compounds consisting of primarily carbon and hydrogen, which may contain any number of other elements, including nitrogen, oxygen, halogens as well... The E1cB reaction mechanism The E1cB elimination reaction is a special type of elimination reaction in organic chemistry. ... n-butyllithium, an organometallic compound. ... The Grignard reaction is an organometallic chemical reaction involving alkyl- or aryl-magnesium halides, also called Grignard reagents, with electrophiles. ... Crown ethers are heterocyclic chemical compounds that, in their simplest form, are cyclic oligomers of ethylene oxide. ... For other uses, see Salt (disambiguation). ... Crown ethers are heterocyclic chemical compounds that, in their simplest form, are cyclic oligomers of ethylene oxide. ...

Adding n-butyllithium to triphenylmethane in THF at low temperatures followed by 12-crown-4 results in a red solution and the salt complex precipitates at -20°C. The central C-C bond lengths are 145 ppm with the phenyl ring propelled at an average angle of 31.2°. An organolithium reagent is a carbon nucleophile similar to a Grignard reagent. ... french: triphényl méthane english: triphenyl methane other: methane triphenyl Boiling point: 78,2 C (from CRC Handbook) Categories: Chemistry stubs ... Tetrahydrofuran, also known as THF, hydrofuran, oxolane, oxacyclopentane, or furanidine, is a heterocyclic organic compound. ... Crown ethers are heterocyclic chemical compounds that, in their simplest form, are cyclic oligomers of ethylene oxide. ... In molecular geometry, bond length or bond distance is the distance between two bonded atoms in a molecule. ...

One tool for the detection of carbanions in solution is proton NMR ^[3]. A spectrum of cyclopentadiene in DMSO shows four vinylic protons at 6.5 ppm and 2 methylene proton at 3 ppm whereas the cyclopentadienyl anion has a single absorption at 5.50 ppm. Pacific Northwest National Laboratorys high magnetic field (800 MHz, 18. ... Cyclopentadiene, with molecular formula C5H6, is a clear, colorless, liquid organic chemical, with an odor reminiscent of turpentine or camphor. ... In chemistry, methylene is a divalent functional group CH2 derived formally from methane. ... --141. ...

Carbon acids

Any molecule containing a C-H can lose a proton forming the carbanion. Hence any hydrocarbon containing C-H bonds can be considered an acid with a corresponding pKa value. Methane is certainly not an acid in its classical meaning yet its estimated pKa is 56. Compare this to acetic acid with pKa 12. The same factors that determine the stability of the carbanion also determine the order in pKa in carbon acids. These values are determined for the compounds either in water in order to compare them to ordinary acids, in dimethyl sulfoxide in which the majority of carbon acid and their anions are soluble or in the gase phase. With DMSO the acidity window solutes is limited to its own pKa of 35.5. In chemistry and biochemistry, acid dissociation constant, the acidity constant, or the acid-ionization constant () is a specific type of equilibrium constant that indicates the extent of dissociation of hydrogen ions from an acid. ... Methane is a chemical compound with the molecular formula CH4. ... Acetic acid, also known as ethanoic acid, is an organic chemical compound best recognized for giving vinegar its sour taste and pungent smell. ... Dimethyl sulfoxide The United States DoDs Defense Modeling and Simulation Office This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...

Starting from methane in table 1, the acidity increases when the anion is stabilized by aromaticity such as in indene and cyclopentadiene, or when the negative charge on carbon can be delocalized in one of three phenyl rings in triphenylmethane. The stabilization can be purely inductive for instance in malononitrile. The α-protons of carbonyl groups are acidic because the negative charge in the enolate can be partially distributed in the oxygen atom. One compound called meldrum's acid, even more acidic than acetic acid and historically named an acid, in fact is a lactone but its acidic carbon protons make it acidic. The acidity of carbonyl compound is an important driving force in many organic reactions such as the Aldol reaction. Cyclopentane is a highly flammable alicyclic hydrocarbon with chemical formula C5H10 and CAS number 287-92-3, consisting of a ring of five carbon atoms each bonded with two hydrogen atoms above and below the plane. ... Methane is a chemical compound with the molecular formula CH4. ... Anisole, also known as methoxybenzene, is a clear, colorless liquid with a pleasant smell similar to that of anise seed. ... Propylene, also known as propene, is a colorless flammable gas with chemical formula C3H6 having a garlic odor. ... Toluene, also known as methylbenzene or phenylmethane is a clear, water-insoluble liquid with the typical smell of paint thinners, redolent of the sweet smell of the related compound benzene. ... Diphenylmethane is a compound consisting of two phenyl groups joined to a single carbon. ... Aniline, phenylamine or aminobenzene (C6H5NH2) is an organic chemical compound which is a primary aromatic amine consisting of a benzene ring and an amino group. ... french: triphényl méthane english: triphenyl methane other: methane triphenyl Boiling point: 78,2 C (from CRC Handbook) Categories: Chemistry stubs ... Xanthene (9H-xanthene, 10H-9-oxaanthracene) is a yellow organic heterocyclic compound. ... Grain alcohol redirects here. ... Phenylacetylene is an alkyne hydrocarbon containing a phenyl group. ... Xanthene Flupenthixol Thioxanthene is a molecule in which the oxygen in a xanthene molecule is replaced with a sulfur. ... The chemical compound acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and β-ketopropane) is the simplest representative of the ketones. ... Benzoxazole is an aromatic organic compound with a molecular formula C7H5NO, a benzene-fused oxazole ring structure, and an odor similar to pyridine. ... Fluorene Fluorene, or 9H-fluorene, is a polycyclic aromatic hydrocarbon. ... Indene is a flammable polycyclic hydrocarbon with chemical formula C9H8 and CAS number 95-13-6. ... Phenylacetylene is an alkyne hydrocarbon containing a phenyl group. ... Cyclopentadiene, with molecular formula C5H6, is a clear, colorless, liquid organic chemical, with an odor reminiscent of turpentine or camphor. ... R-phrases , S-phrases , , , Flash point 34 °C Autoignition temperature 340 °C Explosive limits 2. ... Acetic acid, also known as ethanoic acid, is an organic chemical compound best recognized for giving vinegar its sour taste and pungent smell. ... Malononitrile, also propanedinitrile, is a nitrile, with formula CH2(CN)2. ... Meldrums acid or 2,2-dimethyl-1,3-dioxane-4,6-dione is an organic compound. ... In chemistry and biochemistry, acid dissociation constant, the acidity constant, or the acid-ionization constant () is a specific type of equilibrium constant that indicates the extent of dissociation of hydrogen ions from an acid. ... Dimethyl sulfoxide The United States DoDs Defense Modeling and Simulation Office This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. ... Indene is a flammable polycyclic hydrocarbon with chemical formula C9H8 and CAS number 95-13-6. ... Cyclopentadiene, with molecular formula C5H6, is a clear, colorless, liquid organic chemical, with an odor reminiscent of turpentine or camphor. ... french: triphényl méthane english: triphenyl methane other: methane triphenyl Boiling point: 78,2 C (from CRC Handbook) Categories: Chemistry stubs ... Malononitrile, also propanedinitrile, is a nitrile, with formula CH2(CN)2. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom : C=O. The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e. ... Enol (or, more officially, but less commonly: alkenol) is an alkene with hydroxyl group on one of the carbon atoms of the double bond. ... Meldrums acid or 2,2-dimethyl-1,3-dioxane-4,6-dione is an organic compound. ... Acetic acid, also known as ethanoic acid, is an organic chemical compound best recognized for giving vinegar its sour taste and pungent smell. ... Structure of a carboxylic acid The 3D structure of the carboxyl group A space-filling model of the carboxyl group Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -C(=O)OH, usually written -COOH or -CO2H. [1] Carboxylic acids are Bronsted... A lactone is a cyclic ester in organic chemistry. ... Organic reactions are chemical reactions between organic compounds. ... A typical experimental setup for an aldol reaction. ...

The champion carbon acid is carborane superacid with an acidity one million times stronger than that of sulfuric acid. 3D model of carborane acid, colors: Hydrogen - white, Chlorine - yellow, Boron - green, Carbon - black A carborane is a cluster composed of boron and carbon atoms. ... Sulfuric (or sulphuric) acid, H2SO4, is a strong mineral acid. ...

Chiral carbanions

With the molecular geometry for an carbanion described as a trigonal pyramid the question is whether or not carbanions can display chirality. After all when the activation barrier for inversion of this geometry is too low any attempt at introducing chirality will end in racemization. However, solid evidence exists that carbanions can indeed be chiral for example in research carried out with certain organolithium compounds. Geometry of the water molecule Molecular geometry or molecular structure is the three dimensional arrangement of the atoms that constitute a molecule, inferred from the spectroscopic studies of the compound. ... In chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base. ... The term chiral (pronounced ) is used to describe an object which is non-superimposable on its mirror image. ... In chemistry racemization refers to partial conversion of one enantiomer into another. ... An organolithium reagent is an organometallic compound with a direct bond between a carbon and a lithium atom. ...

The first ever evidence for the existence of chiral organolithium compounds was obtained in 1950. Reaction of chiral 2-iodooctane with sec-butyllithium in petroleum-ether at -70°C followed by reaction with dry ice yielded mostly recemic 2-methylbutyric acid but also an amount of optically active 2-methyloctanoic acid which could only have formed from likewise optical active 2-methylheptyllithium with the carbon atom linked to lithium the carbanion ^[5]: Dry ice is a genericized trademark for solid (frozen) carbon dioxide. ... Butyric acid, (from Greek βουτυρος = butter) IUPAC name n-Butanoic acid, or normal butyric acid, is a carboxylic acid with structural formula CH3CH2CH2-COOH. It is notably found in rancid butter, parmesan cheese, and vomit, and has an unpleasant odor and acrid taste, with a sweetish aftertaste (similar to ether). ... When polarized light is passed through a substance containing chiral molecules (or nonchiral molecules arranged asymmetrically), the direction of polarization can be changed. ...

On heating the reaction to 0°C the optical activity is lost. More evidence followed in the 1960s. A reaction of the cis isomer of 2-methylcyclopropyl bromide with sec-butyllithium again followed by carboxylation with dry ice yielded cis-2-methylcyclopropylcarboxylic acid. The formation of the trans isomer would have indicated that the intermediate carbanion was unstable ^[6]. In chemistry, geometric isomerism is a form of stereoisomerism and describes the orientation of functional groups at the ends of a bond around which no rotation is possible. ... A carboxyl or carboxylic group is a functional group consisting of a carbon atom doubly bonded to an oxygen atom and single-bonded to a hydroxyl (-OH) group. ...

In the same manner the reaction of (+)-(S)-l-bromo-l-methyl-2,2-diphenylcyclopropane with n-butyllithium followed by quench with methanol resulted in product with retention of configuration ^[7]: Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naptha or wood spirits, is a chemical compound with chemical formula CH3OH. It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid with a distinctive odor that is somewhat milder and sweeter than ethanol (ethyl alcohol). ...

Of recent date are chiral methyllithium compounds ^[8]:

The phosphate 1 contains a chiral group with a hydrogen and a deuterium substituent. The stannyl group is replaced by lithium to intermediate 2 which undergoes a phosphate-phosphorane rearrangement to phosphorane 3 which on reaction with acetic acid gives alcohol 4. Once again in the range of -78°C to 0°C the chirality is preserved in this reaction sequence ^[9]. Organophosphorus compounds are chemical compounds containing carbon phosphorus bonds. ... Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen (~154 PPM). ... A phosphorane is a functional group in chemistry with pentavalent phosphorus. ... Functional group of an alcohol molecule. ...

External links

• Large database of Bordwell pKa values at www.chem.wisc.edu Link
• Large database of Bordwell pKa values at daecr1.harvard.edu Link

See also

• Carbocation

A carbocation (IPA pronunciation: ) is an ion with a positively-charged carbon atom. ...

References