2-Methylbutanoic acid, Reactions
The compound and its enantiomers react as typical carboxylic acids: they can form amide, ester, anhydride, and chloride derivatives. The acid chloride is commonly used as the intermediate to obtain the others.


2-Methylbutanoic acid, Uses
Racemic 2-methylbutanoic acid is a slightly volatile, colorless liquid with a pungent cheesy odor. The smell differs significantly between the two enantiomeric forms. (S)-2-Methylbutyric acid has a pleasantly sweet, fruity odor while (R)-2-methylbutanoic acid has a pervasive, cheesy, sweaty odor. The main use of the materials, and their esters, is therefore as flavours and food additives. The compounds' safety in this application was reviewed by an FAO and WHO panel, who concluded that there were no concerns at the likely levels of intake.


2-Methylbutanoic acid, Biology
Since 2-methylbutanoic acid and its esters are natural components of many foods, they are present in mammals including humans.


2-Methylbutyryl-CoA dehydrogenase deficiency
2-Methylbutyryl-CoA dehydrogenase deficiency, is an autosomal recessive metabolic disorder. It causes the body to be unable to process the amino acid isoleucine properly. Initial case reports identified individuals with developmental delay and epilepsy, however most cases identified through newborn screening have been asymptomatic.


2-Methylbutyryl-CoA dehydrogenase deficiency, Signs and symptoms
SBCADD is included as a secondary target condition in most newborn screening programs, as the key analyte is the same as is used to identify isovaleric acidemia. Most cases have been Hmong individuals, who are asymptomatic. There are isolated case reports where individuals have been identified with SBCADD in addition to developmental delay and epilepsy. It is currently unclear what the complete clinical presentation of SBCADD looks like. There is some concern that these cases with additional symptoms may reflect an ascertainment bias rather than being a true representation of the clinical spectrum of the disease. Currently, there is no accepted treatment, as most affected individuals do not require any. Some recommend avoidance of valproic acid, as it can be a substrate for 2-methylbutyryl-CoA dehydrogenase.


2-Methylbutyryl-CoA dehydrogenase deficiency, Cause
The disorder is caused by a mutation in the ACADSB gene, located on the long arm of human chromosome 10 (10q25-q26). It is inherited in an autosomal recessive manner, which means an affected individual must inherit one copy of the mutation from each parent.


2-Methylbutyryl-CoA dehydrogenase deficiency, Diagnosis
Most individuals with SBCADD are identified through newborn screening, where they present with an elevation of a five carbon acylcarnitine species. Confirmatory testing includes plasma and urine analysis to identify the carnitine and glycine conjugates of 2-methylbutyryl-CoA.


2-Methyldodecane
2-Methyldodecane, an organic compound with a chemical formula C13H28, is an isomer of tridecane. It is produced by the reaction of 1-bromodecane and diisopropyl zinc. Reaction of decylmagnesium bromide and 2-bromopropane produce 2-methyldodecane too. Another method to produce 2-methyldodecane is react 1-dodecene and trimethylaluminium.


2-Methyleneglutaronitrile
2-Methylene glutaronitrile is a dimerization product of acrylonitrile and a starting material for di- and triamines, for the biocide 2-bromo-2-(bromomethyl)pentanedinitrile and for heterocycles, such as 3-cyanopyridine.


2-Methyleneglutaronitrile, Preparation
2-Methylene glutaronitrile is a side-product in the production of hexanedinitrile which is used (after hydrogenation to 1,6-diaminohexane) as a key component for engineering polymers such as the polyamides (PA 66) or polyurethanes. Hexanedinitrile can be industrially produced by electrochemical hydrodimerisation or by catalytic dimerization of acrylonitrile.


2-Methyleneglutaronitrile, Preparation
A catalytic tail-tail dimerization of two acrylonitrile molecules forms hexanedinitrile:


2-Methyleneglutaronitrile, Preparation
Also head-to-tail dimerization can occur in the process. In the presence of tricyclohexylphosphine (PCy3) a yield of up to 77% 2-methylene glutaronitrile can be obtained:


2-Methyleneglutaronitrile, Preparation
Metal halides (such as zinc chloride or aluminum chloride) are used with tertiary amines (such as triethylamine) as catalysts for the dimerization. Crude yields of up to 84% are achieved. Often, significant amounts of product are lost during the work-up (e. g. extraction and  distillation) because of the tendency to polymerization of 2-methylene glutaronitrile.


2-Methyleneglutaronitrile, Preparation
In addition to the linear dimerization products 1,4-dicyano-2-butene and 1,4-dicyano-3-butene (obtained as cis-trans isomer mixtures) usually also other oligomers (and polymers) of acrylonitrile are formed. During the electrochemical hydrooligomerization of acrylonitrile, these are trimers, such as 1,3,6- and 1,3,5-tricyanohexane or tetramers, such as 1,3,6,8- and 1,3,5,8-tetracyanooctane. The reaction of acrylonitrile with tributylphosphine affords 2-methyleneglutaronitrile in a modest yield of about 10% after fractional distillation. The DABCO-catalyzed acrylonitrile dimerization of 2,4-dicyano-1-butene after 10 days at room temperature is with 40% yield similarly inefficient.


2-Methyleneglutaronitrile, Use
The earlier patent literature describes processes for the isomerization of 2-methylene glutaronitrile to 1,4-dicyanobutenes as hexanedinitrile precursors, which became obsolete with the optimization of the electrochemical hydrodimerization of acrylonitrile to hexanedinitrile.


2-Methyleneglutaronitrile, Use
In the hydrogenation of 2-methylene glutaronitrile in the presence of palladium on carbon, hydrogen is attached to the double bond and 2-methylglutaronitrile is obtained in virtually quantitative yield.


2-Methyleneglutaronitrile, Use
The hydrogenation of the nitrile groups requires more severe conditions and the presence of ammonia or amines to suppress the formation of secondary amines. This second hydrogenation step is carried out with Raney-cobalt as the hydrogenation catalyst to give 2-methyl-1,5-pentanediamine in 80% yield.


2-Methyleneglutaronitrile, Use
Hydrogenation of 2-methylene glutaronitrile in the presence of ammonia with manganese-containing sodium oxide-doped cobalt catalyst (at 80 to 100 °C and pressures of 200 atm in a tubular reactor) leads to the addition of ammonia to the double bond and directly converts the compound to 2-aminomethyl-1,5-pentanediamine with yields of 66%.


2-Methyleneglutaronitrile, Use
The branched triamine can be used in epoxides and polyurethanes.


2-Methyleneglutaronitrile, Use
2-Methylenglutaronitrile reacts with methanamide upon catalysis with 4-(dimethylamino)-pyridine (DMAP) at 60 °C in 47% yield to give 1-(N-methanoylamino)-2,4-dicyanobutane, from which α- aminomethylglutaric acid is formed by subsequent hydrolysis.


2-Methyleneglutaronitrile, Use
Heating 2-methyleneglutaronitrile with an alkaline ion exchanger, pyridine and water to 150 °C in an autoclave yields the lactam 5-cyano-2-piperidone in 80% yield.


2-Methyleneglutaronitrile, Use
2-Methylene glutaronitrile can be polymerized to various homo- and copolymers via anionic polymerization with sodium cyanide, sodium in liquid ammonia or with butyllithium. However, the polymers are formed only in low yields and show unsatisfactory properties such as intrinsic viscosities and poor mechanical properties.


2-Methyleneglutaronitrile, Use
The main use of 2-methyleneglutaronitrile is as starting material for the broad-spectrum biocide 2-bromo-2-(bromomethyl)pentanedinitrile (methyldibromo-glutaronitrile), which is formed in virtually quantitative yield by the addition of bromine to the double bond.


2-Methyleneglutaronitrile, Use
From the chlorine-analogous 2-chloro-2-(chloromethyl)pentenenitrile, 3-cyanopyridine is obtained by heating to 150 °C with tin(IV)chloride.


2-Methylfuran
2-Methylfuran, also known with the older name of sylvane, is a flammable, water-insoluble liquid with a chocolate odor, found naturally in Myrtle and Dutch Lavenderused as a FEMA GRAS flavoring substance, with the potential for use in alternative fuels.


2-Methylfuran, Manufacture
2-Methylfuran is an article of commerce (chemical intermediate) and is normally manufactured by catalytic hydrogenolysis of furfural alcohol or via a hydrogenation-hydrogenolysis sequence from furfural in the vapor phase.


2-Methylglutaronitrile
2-Methylglutaronitrile is the organic compound with the formula NCCH2CH2CH(CH3)CN. This dinitrile is obtained in the large-scale synthesis of adiponitrile. It is a colorless liquid with an unpleasant odor. It is the starting compound for the vitamin nicotinamide and for the diester dimethyl-2-methylglutarate and the ester amide methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate, which are promoted as green solvents. 2-Methylglutaronitrile is chiral but is mainly encountered as the racemate.


2-Methylglutaronitrile, Occurrence and production
2-Methylglutaronitrile is a by-product of the production of adiponitrile, the precursor of hexamethylenediamine and adipic acid as building blocks for nylon 66.


2-Methylglutaronitrile, Occurrence and production
Starting from 1,3-butadiene or a butadiene-rich C4-section (> 40% by volume) from a naphtha steamcracker in the first stage a mixture of pentenenitriles is obtained through hydrocyanation (using as catalyst Ni0-phosphine [PR3] or phosphite or phosphonite [P(OR)2R]). The mixture contains mainly trans-3-pentenenitrile in addition to the isomers 2-methyl-2-butenenitrile, 4-pentenenitrile and 2-pentenenitrile.


2-Methylglutaronitrile, Occurrence and production
The mixture of monoolefinic C5 mononitriles is isomerized to 3- and 4-pentenenitrile with a hydrocyanation catalyst and a Lewis acid (such as ZnCl2). In the third step, the mixture is reacted with hydrogen cyanide to give a mixture of dinitriles which contains in addition to 2-methylglutaronitrile also adiponitrile and 2-ethylbutanedinitrile.


2-Methylglutaronitrile, Occurrence and production
The 2-methylglutaronitrile-rich fraction has hitherto been combusted as an undesired by-product of adiponitrile production, having the typical composition of about 86 wt% 2-methylglutaronitrile, 11 wt% 2-succinonitrile and 3 wt% adiponitrile.


2-Methylglutaronitrile, Applications
2-methylglutaronitrile can be converted to 3-methylpyridine (β-picoline) by partial hydrogenation.


2-Methylglutaronitrile, Applications
In addition to 3-methylpyridine, 3-methylpiperidine is obtained as a by-product from which further 3-methylpyridine can be obtained by dehydrogenation.


2-Methylglutaronitrile, Applications
Ammonoxidation of 3-methylpyridine on transition metal contacts yields 3-cyanopyridine (nicotinonitrile) in yields of 95%.


2-Methylglutaronitrile, Applications
Hydrogenation of a solution of 2-methylglutaronitrile in ethanol in the presence of Raney cobalt at 15 bar and 100 °C yields 2-methylpentane-1,5-diamine.


2-Methylglutaronitrile, Applications
2-Methylpentanediamine can be converted to 3-methylpiperidine at 300 to 400 °C on a zeolite contact and then dehydrated on a palladium contact to 3-methylpyridine, which can be converted via nicotinonitrile into nicotinamide.


2-Methylglutaronitrile, Applications
The racemic diamine can also be used for the preparation of specific polyamides and after reaction with phosgene to form 2-methylpentane diisocyanate as a reaction component in polyurethanes. Nitrilases regioselectively hydrolyze the ω-nitrile group in α, ω-dinitriles without detectable amide intermediate directly to the carboxyl group. 4-cyanopentanoic acid is formed in high yield.


2-Methylglutaronitrile, Applications
The ammonium salt of 4-cyanopentanoic acid can be converted by catalytic hydrogenation in the presence of methylamine in 1,5-dimethyl-2-piperidone, an environmentally compatible solvent.


2-Methylglutaronitrile, Applications
The hydrolysis of both nitrile groups of 2-methylglutaronitrile with e.g. 20% sodium hydroxide solution at 50 °C and subsequent acidification produces 2-methylglutaric acid.


2-Methylglutaronitrile, Applications
Starting from 2-methylglutaronitrile the hydrolysis to 2-methylglutaric acid can also be accomplished via the 2-methylglutarimide obtained by heating a 2-methylglutaronitrile/water mixture to 275 °C in the presence of a titanium dioxide catalyst in yields of 94%.


2-Methylglutaronitrile, Applications
The reaction of 2-methylglutarimide with e.g. methanol (methanolysis) produces the diester dimethyl-2-methylglutarate in the presence of titanium dioxide or lanthanum oxide. It was commercialized as an environmentally friendly aprotic dipolar solvent under the name Rhodiasolv IRIS with the typical composition 87-89% dimethyl-2-methylglutarate, 9-11% dimethyl 2-ethylbutanedioate and 1-2% dimethyl hexanedioate as a substitute for acetone, dichloromethane, N-methylpyrrolidone and the like.


2-Methylglutaronitrile, Applications
The ester mixture is very similar to so-called dibasic esters, which are commercially available as FlexiSolv DBE esters.


2-Methylglutaronitrile, Applications
The diester can be selectively converted into a mixture of 1- or 5-substituted methyl ester amides with dimethylamine in methanol/sodium methoxide, which is used under the name Rhodiasolv Polarclean as formulation auxiliaries for crop protection preparations. The resulting ester amides are readily biodegradable and good solvents for a variety of different plant protection agents (such as insecticides or fungicides), also compared to the frequently used N-methylpyrrolidone, cyclohexanone or isophorone.


2-Methylglutaronitrile, Applications
Other esteramides are derived, e. g. from 2-methylglutaronitrile which, after alkaline hydrolysis, is converted into 2-methylglutaric acid, cyclized with acetic anhydride to give 2-methylglutaric anhydride, reacted with dimethylamine to form the monoamide, reacted to an acid chloride with thionyl chloride and formed to an ester with more hydrophobic alcohols (like butanols or cyclohexanol).


2-Methylheptane
2-Methylheptane is a branched alkane isomeric to octane. Its structural formula is (CH3)2CH(CH2)4CH3.


2-Methylhexane
2-Methylhexane (C7H16, also known as isoheptane, ethylisobutylmethane) is an isomer of heptane. It is structurally a hexane molecule with a methyl group attached to its second carbon atom. It exists in most commercially available heptane merchandises as an impurity but is usually not considered as impurity in terms of reactions since it has very similar physical and chemical properties when compared to n-heptane (straight-chained heptane).


2-Methylhexane
Being an alkane, 2-methylhexane is insoluble in water, but is soluble in many organic solvents, such as alcohols and ether. However, 2-methylhexane is more commonly considered as a solvent itself. Therefore, even though it is present in many commercially available heptane products, it is not considered as a destructive impurity, as heptane is usually used as a solvent. Nevertheless, by concise processes of distillation and refining, it is possible to separate 2-methylhexane from n-heptane.


2-Methylhexane
Within a group of isomers, those with more branches tend to ignite more easily and combust more completely. Therefore, 2-methylhexane has a lower Autoignition temperature and flash point when compared to heptane. Theoretically 2-methylhexane also burns with a less sooty flame, emitting higher-frequency radiation; however, as heptane and 2-methylhexane differ by only one carbon atom, in terms of branching, both burn with a bright yellow flame when ignited.


2-Methylhexane
Compared to n-heptane, 2-methylhexane also has lower melting and boiling points. A lower density of liquid is found in 2-Methylhexane than heptane.


2-Methylhexane
On the NFPA 704 scale, 2-methylhexane is listed as a reactivity level-0 chemical, along with various other alkanes. In fact, most alkanes are unreactive except in extreme conditions, such as combustion or strong sunlight. At the presence of oxygen and flame, 2-methylhexane, like heptane, combusts mostly completely into water and carbon dioxide. With UV-light and mixed with halogens in solvents, usually bromine in 1,1,1-trichloroethane, a substitution reaction occurs.


2-Methylimidazole
2-Methylimidazole is an organic compound that is structurally related to imidazole with the chemical formula CH3C3H2N2H. It is a white or colorless solid that is highly soluble in polar organic solvents and water. It is a precursor to a range of drugs and is a ligand in coordination chemistry.


2-Methylimidazole, Synthesis and reactions
It is prepared by condensation of glyoxal, ammonia and acetaldehyde, a Radziszewski reaction. Nitration gives 5-nitro derivative.


2-Methylimidazole, Synthesis and reactions
2-Methylimidazole is a sterically hindered imidazole that is used to simulate the coordination of histidine to heme complexes. It can be deprotonated to make imidazolate-based coordination polymers.


2-Methylimidazole, Applications
2-Methylimidazole is a precursor to the several members of the nitroimidazole antibiotics that are used to combat anaerobic bacterial and parasitic infections.


2-Methylimidazole, Safety
It has low toxicity with an LD50 (rat, oral) of 1300 mg/kg, but it is strongly irritating to the skin and eyes.


2-Methylindole
Methylketol or 2-methylindole is a mildly toxic and slightly flammable organic compound which occurs as a white solid which turns brown over time. It has chemical formulaC9H9N.


2-Methylindole
Methylketol is used as an intermediate for synthesizing dyes, pigments, optical brighteners, and pharmaceuticals.


2-Methylisoborneol
2-Methylisoborneol (MIB) is an irregular monoterpene derived from the universal monoterpene precursor geranyl pyrophosphate. MIB and the irregular sesquiterpene geosmin together account for the majority of biologically-caused taste and odor outbreaks in drinking water worldwide. MIB has a distinct earthy or musty odor, which most people can easily smell. The odor detection threshold of MIB is very low, ranging from 0.002 to 0.02 micrograms per liter in water. MIB is also a factor in cork taint in winemaking.


2-Methylisoborneol
MIB is produced by various blue-green algae (cyanobacteria) and filamentous bacteria in the class Actinomyces, and also some other prokaryotes and eukaryotes. The main genera in the cyanobacteria that have been shown to produce MIB include Oscillatoria, Phormidium, and Planktothrix, while the main genus in the Actinomyces that produces MIB is Streptomyces. They give a musty or earthy odor that can be quite strong if an algal bloom is present. Subsequent death of the microorganisms will  release MIB that is trapped in the cells. Along with geosmin, the off flavors caused are issues in the seafood industry. This chemical is the major cause of "muddy" or "dirt" flavors in catfish and crawfish. Cyanobacteria can also produce chemical toxins that have been a problem in drinking water in some cases.


2-Methylmethcathinone
2-Methylmethcathinone (2-MMC) is a recreational designer drug with stimulant effects. It is a substituted cathinone derivative, closely related to better known drugs such as 3-methylmethcathinone and 4-methylmethcathinone (mephedrone). It was first identified in Sweden in 2014, and has subsequently been reported in other European countries such as Poland and Spain.


2-Methylnaphthalene
On February 22, 2014, NASA announced a greatly upgraded database for detecting and monitoring PAHs, including 2-methylnaphthalene, in the universe. According to NASA scientists, over 20% of the carbon in the universe may be associated with PAHs, possible starting materials for the formation of life. PAHs seem to have been formed shortly after the Big Bang, are abundant in the universe, and are associated with new stars and exoplanets.


2-Methylnaphthalene-1,4-diamine
2-Methylnaphthalene-1,4-diamine is a synthetic menadione analog with vitamin K activity.


2-Methylnaphthalene-1,4-diamine
2-Methylnaphthalene-1,4-diamine was first synthetized in 1925. In 1942 two different research groups noted the vitamin K activity of the compound. It forms a dihydrochloride salt (C11H14Cl2N2) with hydrochloric acid and one of the aforementioned research groups suggested the name vitamin K6 for the salt.


2-Methylnaphthalene-1,4-diamine
2-Methylnaphthalene-1,4-diamine and its dihydrochloride can be made from 2-methylnaphthalene or its close analogs. Dihydrochloride blackens without melting at about 300 °C.


2-Methylnaphthalene-1,4-diamine
4-Amino-3-methyl-1-naphthol or its dihydrochloride have not been used as commercial medicinal forms of vitamin K unlike phylloquinone and menadione for example.


2-Methylnaphthalene-1,4-diamine
Oral toxicity of dihydrochloride for rats is approximately the same as for 4-amino-2-methyl-1-naphthol hydrochloride.


2-Methyloctane
2-Methyloctane is a branched alkane hydrocarbon with the chemical formula C9H20. It is a colorless, flammable liquid


2-Methyloctane, Combustion reactions
2-Methyloctane burns in the same way as other alkanes. Where there is enough oxygen, nonane burns to form water and carbon dioxide, so 2-methyloctane would do the same.


2-Methyloctane, Combustion reactions
When insufficient oxygen is present for complete combustion, carbon monoxide is produced.


2-Methylpentamethylenediamine
2-Methylpentamethylenediamine is an organic compound part of the amine family with the formula H2NCH2CH2CH2CH(CH3)CCH2NCH2. A colorless liquid, this diamine is obtained by the hydrogenation of 2-methylglutaronitrile.


2-Methylpentamethylenediamine, Uses
2-Methylpentamethylenediamine serves as a curing agent. It gives good adhesion for metals and resistance against corrosion and other chemicals. It provides toughness, low blush, uniform finish, high gloss, and improves UV stability. It reduces gel time and is compatible with epoxy resins. It is suitable for marine, industrial, and decorative coatings.


2-Methylpentamethylenediamine, Uses
2-Methylpentamethylenediamine can also be used as a chain extender for polyurethane applications. Its derivatives like aspartic esters, secondary amines,  aldimines and ketoimines serve as curatives in systems of polyurea. In polyamides, 2-Methylpentamethylenediamine acts as a crystallinity disruptor. This makes polymers amorphous in structure and slows down crystallization. It lowers melting point, improves surface appearance, increases abrasion resistance, and dye uptake. It also reduces water absorption,  gelling, melt and quench temperatures.


2-Methylpentamethylenediamine, Hazards
Even though 2-Methylpentamethylenediamine has many uses, it also has many hazards. It can cause burns, is corrosive to skin, harmful when swallowed, and it can cause pulmonary edema and acute pneumonitis when inhaled in high concentrations.


2-Methylpentane
2-Methylpentane, trivially known as isohexane, is a branched-chain alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the second carbon atom in a pentane chain.


2-Methylphenethylamine
2-Methylphenethylamine (2MPEA) is an organic compound with the chemical formula of C9H13N. 2MPEA is a human trace amine associated receptor 1 (TAAR1) agonist, a property which it shares with its monomethylated phenethylamine isomers, such as amphetamine (α-methylphenethylamine), β-methylphenethylamine, and N-methylphenethylamine (a trace amine).


2-Methylphenethylamine
Very little data, even on toxicity, is available about its effects on humans other than that it activates the human TAAR1 receptor.


2-Methylpyridine
2-Methylpyridine, or 2-picoline, is the compound described with formula C6H7N. 2-Picoline is a colorless liquid that has an unpleasant odor similar to pyridine. It is mainly used to make vinylpyridine and the agrichemical nitrapyrin.


2-Methylpyridine, Synthesis
2-Picoline was the first pyridine compound reported to be isolated in pure form. It was isolated from coal tar in 1846 by T. Anderson. This chemistry was practiced by Reilly Industries in Indianapolis. It is now mainly produced by two principal routes, the condensation of acetaldehyde, formaldehyde, and ammonia and the cyclization of nitriles and acetylene. One example of such reaction is the combination of acetaldehyde and ammonia:


2-Methylpyridine, Reactions
Most of the reactions of picoline are centered on the methyl group. For example, the principal use of 2-picoline is as a precursor of 2-vinylpyridine. The conversion is achieved by condensation with formaldehyde:


2-Methylpyridine, Reactions
The copolymer of 2-vinylpyridine, butadiene and styrene is used as an adhesive for textile tire cord. 2-Picoline is also a precursor to the agrichemical, nitrapyrin, which prevents loss of ammonia from fertilizers. Oxidation by potassium permanganate affords picolinic acid:


2-Methylpyridine, Reactions, Biodegradation
Like other pyridine derivatives, 2-methylpyridine is often reported as an environmental contaminant associated with facilities processing oil shale or coal, and has also been found at legacy wood treatment sites. The compound is readily degradable by certain microorganisms, such as Arthrobacter sp. strain R1 (ATTC strain number 49987), which was isolated from an aquifer contaminated with a complex mixture of pyridine derivatives. Arthrobacter and closely related Actinobacteria are often found associated with degradation of pyridine derivatives and other nitrogen heterocyclic compounds. 2-methypyridine and 4-methypyridine are more readily degraded and exhibit less volatilization loss from environmental samples than does 3-methypyridine.


2-Methylpyridine, Uses
2-Methylpyridine is an intermediate used in the production of some pharmaceutical drugs including amprolium, picoplatin, dimethindene, and encainide.


2-Methylpyridine, Toxicity
Like most alkylpyridines, the LD50 of 2-methylpyridine is modest, being 790 mg/kg (oral, rat).


2-Methylsuccinic acid
2-Methylsuccinic acid is an organic compound with the formula HO2CCH(CH3)CH2CO2H. A white solid, it is the simplest chiral dicarboxylic acid. It is a recurring component of urban aerosols. Salts and esters of 2-methylsuccinic acid are called 2-methylsuccinates.


2-Methylsuccinic acid, Preparation
It can be prepared by partial hydrogenation of itaconic acid over Raney nickel. Alternatively, hydrocyanation of ethyl crotonate affords an intermediate, which converts to 2-methylsuccinic acid after hydrolysis of the ester and nitrile substituents.


2-Methyltetrahydrofuran
2-Methyltetrahydrofuran (2-MeTHF) is an organic compound with the molecular formula C5H10O. It is a highly flammable, mobile liquid. It is mainly used as a replacement for Tetrahydrofuran (THF) in specialized applications for its better performance, such as to obtain higher reaction temperatures, or easier separations (as, unlike THF, it is not miscible with water). It is derived from sugars via furfural and is occasionally touted as a biofuel.


2-Methyltetrahydrofuran, Structures and  properties
2-Methyltetrahydrofuran is "inversely soluble" in water. That is, its solubility decreases with increasing temperature, which is a rare property. Much like tetrahydrofuran, 2-methyltetrahydrofuran can act as a Lewis base in organometallic reactions. 2-Methyltetrahydrofuran is usually produced as a racemic mixture.


2-Methyltetrahydrofuran, Preparation
Furfural is produced by the acid-catalyzed digestion of pentosan sugars, C5 polysaccharides, in biomass. Thus, the raw materials of 2-methyltetrahydrofuran are renewable biomass rich with cellulose, hemicelluloses, and lignin, such as corncobs or bagasse and other plant and agricultural waste.


2-Methyltetrahydrofuran, Preparation
2-Methyltetrahydrofuran can also be produced starting from levulinic acid. Cyclization and reduction gives γ-valerolactone:


2-Methyltetrahydrofuran, Preparation
γ-Valerolactone can be hydrogenated to 1,4-pentanediol, which can then be dehydrated to give 2-methyltetrahydrofuran:


2-Methyltetrahydrofuran, Applications
2-Methyltetrahydrofuran is mainly used as a higher boiling substitute for tetrahydrofuran as a specialty solvent. It also is used in the electrolyte formulation for secondary lithium electrodes and as a component in alternative fuels. It is a valued solvent for low-temperature reactions. 2-Methyltetrahydrofuran forms a glass, which does not crystallize, and is frequently used as a solvent for spectroscopic studies at −196 °C.


2-Methyltetrahydrofuran, Applications
Other common uses of 2-methyltetrahydrofuran is as a solvent for Grignard reagents used in organometallic and biphasic chemical processes, because of the oxygen atom's ability to coordinate to the magnesium ion component of the Grignard reagent, or to azeotropically dry products. The use of 2-methyltetrahydrofuran provides very clean organic water phase separations. It is a popular, but costlier substitute for tetrahydrofuran.


2-Methyltetrahydrofuran, Applications
2-Methyltetrahydrofuran  is approved by the United States Department of Energy as an additive to gasoline. Furfural and other furyl compounds (furfuryl alcohol, methylfuran, tetrahydrofufuryl alcohol) have a tendency to polymerize and are quite volatile. 2-Methyltetrahydrofuran itself, however, is more stable and less volatile, and thus is suitable for use as a motor fuel.


2-Methyltetrahydrofuran, Applications
2-Methyltetrahydrofuran has been promoted as an ecologically-friendly alternative to THF. Whereas 2-MeTHF is more expensive, it may provide for greater overall process economy. 2 -MeTHF has solvating properties that are intermediate between diethyl ether and THF, has limited water miscibility, and forms an azeotrope with water on distillation. Its lower melting point makes it useful for lower temperature reactions, and its higher boiling point allows procedures under reflux at higher temperatures (relative to THF).


2-Methyltetrahydroquinoline
2-Methyltetrahydroquinoline is one of the methyl-substituted derivatives of tetrahydroquinoline. A colorless oil, it is a chiral compound owing to the presence of the methyl substituent. It is produced by the hydrogenation of quinaldine. It is of interest in medicinal chemistry.


2-Methylthioethylamine
2-Methylthioethylamine is the organosulfur compound with the formula CH3SCH2CH2NH2. It is a colorless liquid. It can be viewed as the product of S-methylation of cysteamine or decarboxylation of S-methylcysteine. The compound is a ligand and, via Schiff base condensations, a ligand precursor.


2-Methylthiophene
2-Methylthiophene is an organosulfur compound with the formula CH3C4H3S. It is a colorless, flammable liquid. It can be produced by Wolff-Kishner reduction of thiophene-2-carboxaldehyde.


2-Methyltridecane
2-Methyltridecane is an organic compound with chemical formula C14H30. It is an isomer of tetradecane. It can be produced by reducing 2,2-dimethyl-3-decylthiirane. Metallic lanthanum in tetrahydrofuran can reduce 2-iodo-2-methyltridecane into 2-methyltridecane. In this reaction, the byproducts include 12,12,13,13-tetramethyltetracosane and some alkenes. Adding hydrogen to 13-bromo-2-methyldecan-2-ol  can produce some 2-methyltridecane. This reaction is catalyzed by Raney nickel.


2-Methylundecanal
2-Methylundecanal is an organic compound that is found naturally in kumquat peel oil. This compound smells herbaceous, orange, and ambergris-like. At high dilution it has a flavor similar to honey and nuts. It is a colorless or pale yellow liquid that is soluble in organic solvents such as ether and ethanol. It is used as a fragrance component in soaps, detergents, and perfumes.


2-Methylundecanal, Preparation
The first synthesis of 2-methylundecanal was recorded by Georges Darzens in 1904 from methyl nonyl ketone and ethyl chloroacetate. This method of synthesis can be used to produce a variety of aldehydes and became known as the Darzens reaction and is still used today. 2-Methylundecanal is synthesized in industry by two main routes. The first route, like Darzens, involves converting methyl nonyl ketone to its glycidate by allowing it to react with alkyl chloroacetate. The glycidate then undergoes saponification followed by decarboxylation.


2-Methylundecanal, Preparation
The second method for the synthesis of 2-methylundecanal begins with the conversion of undecanal to 2-methyleneundecanal by allowing it to react with formaldehyde in the presence of base. The 2-methyleneundecanal is then hydrogenated to give 2-methylundecanal. The required undecanal is generated from 1-decene by hydroformylation. The resulting solution is over 50% 2-methyleneundecanal. The double bond of this compound is hydrogenated and the resulting 2-methylundecanal is separated from the by-products using fractional distillation.


2-Methylundecanal, Chirality
The enantiomers can be synthesized with high enantiomeric purity using the SAMP/ RAMP hydrazone method. This process involves starting with simple achiral aldehydes and converting them to their SAMP hydrazones then obtaining the corresponding chiral hydrazones using RAMP as a chiral auxiliary. The chiral hydrazones are then metalated with lithium diisopropylamide (LDA) and alkylated with a slight excess of dimethyl sulfate. Testing of the enantiomers by a professional perfumer indicated only a slight difference in odor quality and intensity.


2-Methylundecanal, Applications
2-Methylundecanal is used widely as a fragrance element in soaps and detergents as well as in the perfume industry to give conifer notes, fir in particular, but is also used in fantasy compositions. This aldehyde was one of the first synthetics to be used in a prestigious perfume, namely Chanel No. 5.


2-NBDG
2-NBDG is a fluorescent tracer used for monitoring glucose uptake into living cells; it consists of a glucosamine molecule substituted with a 7-nitrobenzofurazan fluorophore at its amine group. It is widely referred to a fluorescent derivative of glucose, and it is used in cell biology to visualize uptake of glucose by cells. Cells that have taken up the compound fluoresce green.


2-NBDG
2-NBDG is similar to radiolabeled glucose in that both can be used to detect glucose transport. Unlike radiolabeled glucose, 2-NBDG is compatible with fluorescence techniques such as a fluorescent microscopy, flow cytometry, and fluorimetry


2-NBDG
The compound is taken up by a variety of mammalian, plant, and microbial cells   In mammalian cells, one transporter for 2-NBDG is GLUT2. In bacterial cells, the predominant transporter is the mannose phosphotransferase system. Cells that lack these or other compatible transporters do not take up 2-NBDG.


2-NBDG
Like glucose, 2-NBDG is transported according to Michaelis–Menten kinetics. However, transport of 2-NBDG has a lower Vmax  (maximum rate), and thus the rate of transport is generally slower than glucose.


2-NBDG
Once taken up, the compound is metabolized to a non-fluorescent derivative, as shown in Escherichia coli. The identity and further metabolism of this non-fluorescent derivative has not been established.


2-Naphthalenethiol
2-Naphthalenethiol is an organosulfur compound with the formula C10H7SH. It is a white solid. It is one of two monothiols of naphthalene, the other being 1-naphthalenethiol.


2-Naphthalenethiol, Synthesis and reactions
2-Naphthalenethiol is prepared from 2-naphthol by the Newman–Kwart rearrangement using the thiocarbamate. It undergoes lithiation at the 1 and 3-position.


2-Naphthoic acid
2-Naphthoic acid is an organic compound of the formula C10H7CO2H. It is one of two isomeric carboxylic acid derivatives of naphthalene, the other one being 1-naphthoic acid. It can be prepared by carboxylation of 1-chloronaphthalene. Its pKa is 4.2.


2-Naphthol
2-Naphthol, or β-naphthol, is a fluorescent colorless (or occasionally yellow) crystalline solid with the formula C10H7OH. It is an isomer of 1-naphthol, differing by the location of the hydroxyl group on the naphthalene ring. The naphthols are naphthalene homologues of phenol, but more reactive. Both isomers are soluble in simple alcohols, ethers, and chloroform. 2-Naphthol is a widely used intermediate for the production of dyes and other compounds.


2-Naphthol, Production
Traditionally, 2-naphthol is produced by a two-step process that begins with the sulfonation of naphthalene in sulfuric acid:


2-Naphthol, Production
The sulfonic acid group is then cleaved in molten sodium hydroxide:


2-Naphthol, Production
2-Naphthol can also be produced by a method analogous to the cumene process.


2-Naphthol, 2-Naphthol-derived dyes
The Sudan dyes are popular dyes noted for being soluble in organic solvents. Several of the Sudan dyes are derived from 2-naphthol by coupling with diazonium salts. Sudan dyes I -IV and Sudan Red G consist of arylazo-substituted naphthols.


2-Naphthol, Reactions
2-Naphthol reacts to form BINOL, a C2-symmetric ligand popularized for use in asymmetric catalysis.


2-Naphthol, Reactions
2-Naphthol converts to 2-naphthalenethiol via reaction with dimethylthiocarbamoyl chloride via the Newman-Kwart rearrangement.


2-Naphthol, Safety
Naphthols (both 1 and 2 isomers) are used as biomarkers for livestock and humans exposed to polycyclic aromatic hydrocarbons.


2-Naphthylamine
2-Naphthylamine is one of two isomeric aminonaphthalenes, compounds with the formula C10H7NH2. It is a colorless solid, but samples take on a reddish color in air because of oxidation. It was formerly used to make azo dyes, but it is a known carcinogen and has largely been replaced by less toxic compounds.


2-Naphthylamine, Preparation
2-Naphthylamine is prepared by heating 2-naphthol with ammonium zinc chloride to 200-210 °C, the Bucherer reaction. Its acetyl derivative can be obtained by heating 2-naphthol with ammonium acetate to 270-280 °C.


2-Naphthylamine, Reactions
It gives no color with iron(III) chloride. When reduced by sodium in boiling amyl alcohol solution, it forms tetrahydro-3-naphthylamine, which exhibits the properties of the aliphatic amines in that it is strongly alkaline in reaction, has an ammoniacal odor and cannot be diazotized.


2-Naphthylamine, Reactions
Numerous sulfonic acid derivatives of 2-naphthylamine are used in commerce, such as precursors to dyes. Owing to the carcinogenicity of the amine, these derivatives are mainly prepared by amination of the corresponding naphthols. Of them, the δ-acid and Bronner's acid are of more value technically, since they combine with ortho-tetrazoditolyl to produce fine red dye-stuffs.


2-Naphthylamine, Reactions
2-Naphthylamine was previously used as a dye precursor and rubber antioxidant in the 1930s, 40s and 50s. Dupont stopped using it in the 1970s.


2-Naphthylamine, Role in disease
2-Naphthylamine is found in cigarette smoke and suspected to contribute to the development of bladder cancer.


2-Naphthylamine, Role in disease
It is activated in the liver but quickly deactivated by conjugation to glucuronic acid. In the bladder, glucuronidase re-activates it by deconjugation, which leads to the development of bladder cancer.


2-Nitroaniline
2-Nitroaniline is an organic compound with the formula H2NC6H4NO2. It is a derivative of aniline, carrying a nitro functional group in position 2. It is mainly used as a precursor to o-phenylenediamine.


2-Nitroaniline, Synthesis
2-Nitroaniline is prepared commercially by the reaction of 2-nitrochlorobenzene with ammonia:


2-Nitroaniline, Synthesis
Many other methods exist for the synthesis of this compound. Direct nitration of aniline is inefficient since anilinium is produced instead. Nitration of acetanilide gives only traces of 2-nitro isomer is obtained due to the great steric effect of the amide. Sulfonation is usually used to block the 4 position and increases the effectiveness to 56%.


2-Nitroaniline, Uses and reactions
2-Nitroaniline is the main precursor to phenylenediamines, which are converted to benzimidazoles, a family of heterocycles that are key components in pharmaceuticals.


2-Nitroaniline, Uses and reactions
Aside from its reduction to phenylenediamine, 2-nitroaniline undergoes other reactions anticipated for aromatic amines. It is protonated to give the anilinium salts. Owing to the influence of the nitro substituent, the amine exhibits a basicity nearly 100,000x lower than aniline itself. Diazotization gives diazonium derivative, which is a precursor to some diazo dyes. Acetylation affords 2-nitroacetanilide.


2-Nitrobenzaldehyde
2-Nitrobenzaldehyde is an organic aromatic compound containing a nitro group ortho to formyl. 2 -Nitrobenzaldehyde once was produced as an intermediate in the synthesis of the popular dye Indigo.


2-Nitrobenzaldehyde, Synthesis
The main routes to nitrobenzaldehyde begin with the nitration of styrene and cinnamic acid followed by the conversions of the resulting  2-nitrostyrene and 2-nitrocinnamic acids. Cinnamaldehyde can also be nitrated, e.g., in a solution of acetic anhydride in acetic acid, in high-yield to 2-nitrocinnamaldehyde. This compound is then oxidized to 2-nitrocinnamic acid, which is decarboxylated to the 2-nitrostyrene. The vinyl group can be oxidized in a number of different ways to yield 2-nitrobenzaldehyde.


2-Nitrobenzaldehyde, Synthesis
In one synthetic process, toluene is mono-nitrated at cold temperatures to 2-nitrotoluene, with about 58% being converted to the ortho- isomer, the remaining forming meta- and para- isomers. The 2-nitrotoluene can then be oxidized to yield 2-nitrobenzaldehyde.


2-Nitrobenzaldehyde, Synthesis
Alternatively, 2-nitrotoluene as formed above can be halogenated to a 2-nitrobenzyl halide followed by oxidation with DMSO and sodium bicarbonate to yield 2-nitrobenzaldehyde, which is subsequently purified with the creation of a bisulfite adduct.


2-Nitrobenzaldehyde, Synthesis
The nitration of benzaldehyde produces mostly 3-nitrobenzaldehyde, with yields being about 19% for the ortho-, 72% for the meta- and 9% for the para isomer. For this reason, the nitration of benzaldehyde to yield 2-nitrobenzaldehyde is not cost-effective.


2-Nitrobenzaldehyde, Uses
2-Nitrobenzaldehyde is an intermediate in an early route to indigo, a water-insoluble dye commonly used to dye jeans and other fabrics. In the Baeyer-Drewson indigo synthesis, 2-nitrobenzaldehyde condenses with acetone in basic aqueous solution to yield indigo in a one-pot synthesis. The method was abandoned in the early part of the 20th century, being replaced by routes from aniline.


2-Nitrobenzaldehyde, Uses
Given its two relatively reactive groups, 2-nitrobenzaldehyde is a potential starting material for other compounds. Substituted 2-nitrobenzaldehydes can also be used to yield other important compounds based on indigo, such as indigo carmine.


2-Nitrobenzaldehyde, Uses
2-Nitrobenzaldehyde has been shown to be a useful photoremovable protecting group for various functions.


2-Nitrobenzoic acid
2-Nitrobenzoic acid is an organic compound with the formula C6H4(NO2)CO2H. It is prepared by oxidation of 2-nitrotoluene with nitric acid.


2-Nitrochlorobenzene
2-Nitrochlorobenzene is an organic compound with the formula ClC6H4NO2. It is one of three isomeric nitrochlorobenzenes. It is a yellow crystalline solid that is important as a precursor to other compounds due to its two functional groups.


2-Nitrochlorobenzene, Synthesis
Nitrochlorobenzene is typically synthesized by nitration of chlorobenzene in the presence of sulfuric acid:


2-Nitrochlorobenzene, Synthesis
This reaction affords a mixture of isomers. Using an acid ratio of 30/56/14, the product mix is typically 34-36% 2-nitrochlorobenzene and 63-65% 4-nitrochlorobenzene, with only about 1% 3-nitrochlorobenzene.


2-Nitrochlorobenzene, Reactions
Alkylation and electrophilic aromatic substitution can occur at the chlorinated carbon center, and a diverse array of reactions can be carried out using the nitro group. 2 -Nitrochlorobenzene can be reduced to the 2-chloroaniline with Fe/HCl mixture, the Bechamp reduction. Treatment of 2-nitrochlorobenzene with sodium methoxide gives 2-nitroanisole.


2-Nitrochlorobenzene, Applications
2-Nitrochlorobenzene is not valuable in itself but is a precursor to other useful compounds. The compound is particularly useful because both of its reactive sites can be utilized to create further compounds that are mutually ortho. Its derivative 2-chloroaniline is a precursor to 3,3’-dichlorobenzidine, itself a precursor to many dyes and pesticides.


2-Nitrocinnamaldehyde
2-Nitrocinnamaldehyde, ortho-nitrocinnamaldehyde or o-nitrocinnamaldehyde is an organic aromatic compound containing a nitro group ortho- to the 1-position of cinnamaldehyde.


2-Nitrocinnamaldehyde, Synthesis
2-Nitrocinnamaldehyde can be synthesized by dissolving cinnamaldehyde to a solution of acetic anhydride in acetic acid, and adding a stoichiometric amount of concentrated nitric acid at 0–5 °C. Yields are around 36-46% of theoretical.


2-Nitrocinnamaldehyde, Synthesis
Nitration of cinnamaldehyde via acidification of a nitrate salt with H2SO4 also yields the ortho-nitro compound, however it also yields some of the para-nitro compound, which is generally undesired.


2-Nitrocinnamaldehyde, Synthesis
2-Nitrocinnamaldehyde can also be prepared by reacting 2-nitrobenzaldehyde with acetaldehyde in a condensation reaction.


2-Nitrocinnamaldehyde, Uses
2-Nitrocinnamaldehyde can be oxidized to 2-nitrocinnamic acid which can be used in the Baeyer-Emmerling indole synthesis to produce indole and substituted indoles.


2-Nitrodiphenylamine
2-Nitrodiphenylamine, also called NDPA, 2-NDPA, 2NO2DPA, Sudan Yellow 1339, C.I. 10335, CI 10335, phenyl 2-nitrophenylamine, 2-nitro-N-phenylaniline, or N-phenyl-o-nitroaniline, is an organic chemical, a nitrated aromatic amine, a derivate of diphenylamine. Its chemical formula is C12H10N2O2, or C6H5NHC6H4NO2. It is a red crystalline solid, usually in form of flakes or powder, with melting point of 74-76 °C and boiling point of 346 °C. It is polar but hydrophobic.


2-Nitrodiphenylamine
2-Nitrodiphenylamine is used as a stabilizer for synthetic rubbers, explosives, propellants (e.g. in Otto fuel II, smokeless powders, in some US Army double-base propellants in solid rockets, and in other applications involving nitric acid esters), plastics, and lubricants. It is also an intermediate for organic synthesis, and a civilian solvent dye.


2-Nitrodiphenylamine
In some explosives, it is used to control the explosion. One of its major uses is to control the explosion rate of propylene glycol dinitrate.


2-Nitrodiphenylamine
As a stabilizer, its major role is to eliminate the acidic nitrates and nitrogen oxides produced by gradual decomposition of nitric acid esters, which would otherwise autocatalyze further decomposition. Its amount is usually 1-2% of the mixture; higher amounts than 2% degrade the propellant's ballistic properties. The amount of the stabilizer depletes with time; remaining content of less than 0.5% (with initial 2% content) requires increased surveillance of the munition, with less than 0.2% warranting immediate disposal, as the depletion of the stabilizer may lead to autoignition of the propellant.


2-Nitrodiphenylamine
Other stabilizers of a similar nature are 4-nitrodiphenylamine, N-nitrosodiphenylamine. While N-methyl-p-nitroaniline(MNA also used in IMX-101), and diphenylamine(DPA) are more commonly employed.


2-Nitrofluorene
2-Nitrofluorene is a by-product of combustion and is a nitrated polycyclic aromatic hydrocarbon (fluorene). 2 -Nitrofluorene is listed as an IARC Group 2B carcinogen, indicating it is possibly carcinogenic to humans.


2-Nitropropane
2-Nitropropane (2-NP) is a solvent. It is a colorless liquid and is classified as a nitro compound.


2-Nitropropane, Preparation
2-Nitropropane is produced by the high-temperature vapor-phase nitration of propane, usually with impurities of 1-nitropropane. 2-Nitropropane is also produced as a volatile by-product that can be captured during Leonard's ring-closure hydantoin preparation.


2-Nitropropane, Uses
2-Nitropropane is used as a solvent or additive in inks, paints, adhesives, varnishes, polymers, resins, fuel, and coatings. It is also used as a feedstock for other industrial chemicals, and also in the synthesis of pharmaceuticals such as phentermine, chlorphentermine, and teclozan. It serves as an oxidant in the Hass–Bender oxidation process.


2-Nitropropane, Safety
2-Nitropropane  is a constituent of tobacco smoke. Based on studies in animals, it is reasonably anticipated to be a human carcinogen and it is listed as an IARC Group 2B carcinogen.


2-Nitrotoluene
2-Nitrotoluene or ortho-nitrotoluene is an organic compound with the formula CH3C6H4NO2. It is pale yellow liquid that crystallizes in two forms, called α (−9.27 °C) and β (−3.17 °C). It is mainly a precursor to o-toluidine, which is an intermediate in the production of various dyes.


2-Nitrotoluene, Synthesis and reactions
It is made by nitrating toluene at above -10 °C. This reaction affords a 2:1 mixture of 2-nitro and 4-nitro isomers.


2-Nitrotoluene, Synthesis and reactions
Chlorination of 2-nitrotoluene gives two isomers of the chloronitrotoluenes. Similarly nitration gives two isomers of dinitrotoluene.


2-Nitrotoluene, Synthesis and reactions
2-Nitrotolune is mainly consumed in the production of o-toluidine, a precursor to dyes.


2-Nonanol
2-Nonanol is a simple alcohol. It has the odor of cucumber, and has been identified in oysters. It is used by several insects as pheromones. It is commercially available.


2-Nonenal
2-Nonenal is an unsaturated aldehyde. The colorless liquid is an important aroma component of aged beer and buckwheat.


2-Nonenal, Odor characteristics
The odor of this substance is perceived as orris, fat and cucumber. Its odor has been associated with human body odor alterations during aging.


2-Norbornyl cation
In organic chemistry, the term 2-norbornyl cation (or 2-bicyclo[2.2.1]heptyl cation) describes one of the three carbocations formed from derivatives of norbornane. Though 1-norbornyl and 7-norbornyl cations have been studied, the most extensive studies and vigorous debates have been centered on the exact structure of the 2-norbornyl cation.


2-Norbornyl cation
The 2-norbornyl cation has been formed from a variety of norbornane derivatives and reagents. First reports of its formation and reactivity published by Saul Winstein sparked controversy over the nature of its bonding, as he invoked a three-center two-electron bond to explain the stereoselectivity of the resulting product. Herbert C. Brown challenged this assertion on the grounds that classical resonance structures could explain the stereospecificity without needing to adapt a new perspective of bonding. Both researchers' views had its supporters, and dozens of scientists contributed ingeniously designed experiments to provide evidence for one viewpoint or the other. Over time, the dispute became increasingly bitter and acrimonious, and the debate took on a personal or ad hominem character.


2-Norbornyl cation
Evidence of the non-classical nature of the 2-norbornyl cation grew over the course of several decades, mainly through spectroscopic data gathered using methods such as nuclear magnetic resonance (NMR). Crystallographic confirmation of its non-classical nature did not come until 2013. Although most chemists now agree that 2-norbornyl cation itself is non-classical, it is also widely recognized that the energetic landscape for carbocations tends to be "flat", with many potential structures differing only minutely in energy. Certainly, not all bicyclic carbocations are non-classical; the energy difference between classical and non-classical structures is often delicately balanced. Thus, certain alkyl-substituted 2-bicyclo[2.2.1]heptyl cations are now known to adopt classical structures.


2-Norbornyl cation
The nature of bonding in the 2-norbornyl cation incorporated many new ideas into the field’s understanding of chemical bonds. Similarities can be seen between this cation and others, such as boranes.


2-Norbornyl cation, Theory
The nature of bonding in the 2-norbornyl cation was the center of a vigorous, well-known debate in the chemistry community through the middle of the twentieth century. While the majority of chemists believed that a three-center two-electron bond best depicted its ground state electronic structure, others argued that all data concerning the 2-norbornyl cation could be explained by depicting it as a rapidly equilibrating pair of cations.


2-Norbornyl cation, Theory
At the height of the debate, all chemists agreed that the delocalized picture of electron bonding could be applied to the 2-norbornyl cation. But this did not answer the fundamental question on which the debate hinged. Researchers continued to search for novel ways to determine whether the three-centered delocalized picture described a low-energy transition state (saddle point on the multidimensional potential energy surface) or a potential energy minimum in its own right. Proponents of the "classical" picture believed that the system was best described by a double-well potential with a very low barrier, while those in the "non-classical" camp envisioned the delocalized electronic state to describe a single potential energy well.


2-Norbornyl cation, Theory, Hypovalency: the non-classical picture
Advocates of the non-classical nature of the stable 2-norbornyl cation typically depict the species using either resonance structures or a single structure with partial bonds (see Figure 2).


2-Norbornyl cation, Theory, Hypovalency: the non-classical picture
This hypovalent interaction can be imagined as the net effect of i) a partial sigma bond between carbons 1 and 6, ii) a partial sigma bond between carbons 2 and 6, and iii) a partial pi bond between carbons 1 and 2. Each partial bond is represented as a full bond in one of the three resonance structures or as a dashed partial bond if the cation is depicted through a single structure.


2-Norbornyl cation, Theory, Hypovalency: the non-classical picture
There has been some debate over how much the pi-bonded resonance structure actually contributes to the delocalized electronic structure. Through 1H and 13C NMR spectroscopy, it has been confirmed that little positive charge lies on methylene carbon 6. This is unsurprising as primary carbocations are much less stable than secondary carbocations. However, the 2-norbornyl cation can be formed from derivatives of β-(Δ3-cyclopentenyl)-ethane, indicating that the pi-bonded resonance structure is significant.


2-Norbornyl cation, Theory, Hypovalency: the non-classical picture
The 2-norbornyl cation was one of the first examples of a non-classical ion. Non -classical ions can be defined as organic cations in which electron density of a filled bonding orbital is shared over three or more centers and contains some sigma-bond character. The 2-norbornyl cation is seen as the prototype for non-classical ions. Other simple cations such as protonated acetylene (ethynium, C2H+3), protonated ethylene (ethenium, C2H+5), and protonated ethane (ethanium, C2H+7) have been shown to be best described as non-classical through infrared spectroscopy.


2-Norbornyl cation, Theory, Hypovalency: the non-classical picture
The most frequently proposed molecular orbital depiction of the 2-norbornyl cation is shown in Figure 3. Two p-type orbitals, one on each of carbons 1 and 2, interact with a sp3-hybridized orbital on carbon 6 to form the hypovalent bond. Extended Hückel Theory calculations for the 2-norbornyl cation suggest that the orbital on carbon 6 could instead be sp2-hybridized, though this only affects the geometry of the geminal hydrogens.


2-Norbornyl cation, Theory, Rapid equilibrium: the classical picture
According to proponents of a classical double-well potential, the 2-norbornyl cation exists in dynamic equilibrium between two enantiomeric asymmetric structures. The delocalized species central to the non-classical picture is merely a transition state between the two structures. Wagner-Meerwein rearrangements are invoked as the mechanism that converts between the two enantiomers (see Figure 4).


2-Norbornyl cation, Theory, Rapid equilibrium: the classical picture
Efforts to isolate the asymmetric species spectroscopically are typically unsuccessful. The major reason for this failure is reported to be extremely rapid forward and reverse reaction rates, which indicate a very low potential barrier for interconversion between the two enantiomers.


2-Norbornyl cation, Theory, Nortricyclonium: another non-classical structure
Some chemists have also considered the 2-norbornyl cation to be best represented by the nortricylconium ion, a C3-symmetric protonated nortricyclene. This depiction was first invoked to partially explain results of a 14C isotope scrambling experiment. The molecular orbital representation of this structure involves an in-phase interaction between sp2-hybridized orbitals from carbons 1, 2 and 6 and the 1s atomic orbital on a shared hydrogen atom (see Figure 5).


2-Norbornyl cation, History, Non-classical ions
Non -classical ions differ from traditional cations in their electronic structure: though chemical bonds are typically depicted as the sharing of electrons between two atoms, stable non-classical ions can contain three or more atoms that share a single pair of electrons. In 1939, Thomas Nevell and others attempted to elucidate the mechanism for transforming camphene hydrochloride into isobornyl chloride. In one of the proposed reaction mechanisms depicted in the paper, the positive charge of an intermediate cation was not assigned to a single atom but rather to the structure as a whole.


2-Norbornyl cation, History, Non-classical ions
This was later cited by opponents of the non-classical description as the first time that a non-classical ion was invoked. However, the term "non-classical ion" did not explicitly appear in the chemistry literature until over a decade later, when it was used to label delocalized bonding in a pyramidal, butyl cation.


2-Norbornyl cation, History, Non-classical ions
The term synartetic ion was also invoked to describe delocalized bonding in stable carbocations before the term non-classical ion was in widespread use. The first users of this term commented on the striking similarity between bonding in these types of cations and bonding in borohydrides.


2-Norbornyl cation, History, First non-classical proposals
In 1949, Saul Winstein observed that 2-exo-norbornyl brosylate (p-bromobenzenesulfonate) and 2-endo-norbornyl tosylate (p-toluenesulfonate) gave a racemic mixture of the same product, 2-exo-norbornyl acetate, upon acetolysis (see Figure 6). Since tosylates and brosylates work equally well as leaving groups, he concluded that both the 2-endo and 2-exo substituted norbornane must be going through a common cationic intermediate with a dominant exo reactivity. He reported that this intermediate was most likely a symmetric, delocalized 2-norbornyl cation. It was later shown via vapor phase chromatography that the amount of the endo epimer of product produced was less than 0.02%, proving the high stereoselectivity of the reaction.


2-Norbornyl cation, History, First non-classical proposals
When a single enantiomer of 2-exo-norbornyl brosylate undergoes acetolysis, no optical activity is seen in the resulting 2-exo-norbornyl acetate (see Figure 7). Under the non-classical description of the 2-norbornyl cation, the plane of symmetry present (running through carbons 4, 5, and 6) allow equal access to both enantiomers of the product, resulting in the observed racemic mixture.


2-Norbornyl cation, History, First non-classical proposals
It was also observed that the 2-exo-substituted norbornanes reacted 350 times faster than the corresponding endo isomers. Anchimeric assistance of the sigma bond between carbons 1 and 6 was rationalized as the explanation for this kinetic effect. Importantly, the invoked anchimeric assistance led many chemists to postulate that the energetic stability of the 2-norbornyl cation was directly due to the symmetric, bridged structure invoked in the non-classical explanation. However, some other authors offered alternative explanations for the high stability without invoking a non-classical structure.


2-Norbornyl cation, History, First non-classical proposals
In 1951, it was first suggested that the 2-norbornyl cation could actually be better described when viewed as a nortricyclonium ion. It has been shown that the major product formed from an elimination reaction of the 2-norbornyl cation is nortricyclene (not norbornene), but this has been claimed to support both non-classical ion postulates.


2-Norbornyl cation, History, Herbert C. Brown: a dissenting view
Herbert C. Brown did not believe that it was necessary to invoke a new type of bonding in stable intermediates to explain the interesting reactivity of the 2-norbornyl cation. Criticizing many chemists for disregarding past explanations of reactivity, Brown argued that all of the aforementioned information about the 2-norbornyl cation could be explained using simple steric effects present in the norbornyl system. Given that an alternative explanation using a rapidly equilibrating pair of ions for describing the 2-norbornyl cation was valid, he saw no need to invoke a stable, non-classical depiction of bonding.


2-Norbornyl cation, History, Herbert C. Brown: a dissenting view
Invoking stable non-classical ions was becoming commonplace; Brown felt that this was not only unwarranted but also counterproductive for the field of chemistry as a whole. Indeed, many papers reporting stable non-classical ions were later retracted for being unrealistic or incorrect. After publishing this controversial view in 1962, Brown began a quest to find experimental evidence incompatible with the delocalized picture of bonding in the 2-norbornyl cation.


2-Norbornyl cation, History, Herbert C. Brown: a dissenting view
Brown also worked to prove the instability of a delocalized electronic structure for the 2-norbornyl cation. If the non-classical ion could be proven to be higher in energy than the corresponding classical ion pair, the non-classical ion would only be seen as a transition state between the two asymmetric cations. Though he did not rule out the possibility of a delocalized transition state Brown continued to reject the proposed reflectional symmetry of the 2-norbornyl cation, even late in his career.


2-Norbornyl cation, History, Impact
The introduction of the three-centered two-electron delocalized bond invoked in the non-classical picture of the 2-norbornyl cation allowed chemists to explore a whole new realm of chemical bonds. Chemists were eager to apply the characteristics of hypovalent electronic states to new and old systems alike (though several got too carried away). One of the most fundamentally important concepts that emerged from the intense research focused around non-classical ions was the idea that electrons already involved in sigma bonds could be involved with reactivity.


2-Norbornyl cation, History, Impact
Though filled pi orbitals were known to be electron donors, chemists had doubted that sigma orbitals could function in the same capacity. The non-classical description of the 2-norbornyl cation can be seen as the donation of an electron pair from a carbon-carbon sigma bond into an empty p-orbital of carbon 2. Thus this carbocation showed that sigma-bond electron donation is as plausible as pi-bond electron donation.


2-Norbornyl cation, History, Impact
The intense debate that followed Brown’s challenge to non-classical ion proponents also had a large impact on the field of chemistry. In order to prove or disprove the non-classical nature of the 2-norbornyl cation, chemists on both sides of the debate zealously sought out new techniques for chemical characterization and more innovative interpretations of existing data. One spectroscopic technique that was further developed to investigate the 2-norbornyl cation was nuclear magnetic resonance spectroscopy of compounds in highly acidic media.


2-Norbornyl cation, History, Impact
Comparisons of the 2-norbornyl cation to unstable transition states with delocalized electronic states were often made when trying to elucidate whether the norbornyl system was stable or not. These efforts motivated closer investigations of transition states and vastly increased the scientific community’s understanding of their electronic structure. In short, vigorous competition between scientific groups led to an extensive research and a better understanding of the underlying chemical concepts.


2-Norbornyl cation, Formation
The 2-norbornyl cation can be made by a multitude of synthetic routes. These routes can be grouped into three different classes: σ Formation, π Formation, and Formation by Rearrangement. Each of these is discussed separately below.


2-Norbornyl cation, Formation, σ formation
The starting material for this route is a norbornane derivative with a good leaving group in position 2. If the leaving group is on the exo- face, electron density from the σ bond between carbons 1 and 6 is donated into the σ* antibond between carbon 2 and the leaving group (see Figure 8b).


2-Norbornyl cation, Formation, σ formation
If the leaving group is on the endo- face, the leaving group first leaves on its own. Then electron density from the σ bond between carbons 1 and 6 is donated into the resulting empty atomic orbital on carbon 2. However, this formation route is much slower than that of the exo- isomer because the σ bond cannot provide anchimeric assistance for the first step, making the activation energy to the first transition state much higher. Additionally, if there is a high concentration of reactive electrophiles in the reaction mixture, formation of a newly substituted norbornane derivative may preclude non-classical ion formation.


2-Norbornyl cation, Formation, σ formation
An example of this formation route is the reaction that led Winstein and Trifan to propose the delocalized structure of the 2-norbornyl cation. 2-norbornyl tosylates and brosylates form the 2-norbornyl cation through this route as an intermediate towards solvolysis.


2-Norbornyl cation, Formation, π formation
The starting material for this route is a β-(Δ3-cyclopentenyl)-ethane derivative with a good leaving group on the terminal carbon of the ethane group. Electron density from the π bond of the alkene moiety is donated into the σ* anti-bond between the terminal carbon and the leaving group (see Figure 8c).


2-Norbornyl cation, Formation, π formation
For example, the major product of the acetolysis of β-(Δ3-cyclopentenyl)-ethyl nosylate (p-nitrobenzenesulfonate) is 2-exo-norbornyl acetate. The dearth of β-(Δ3-cyclopentenyl)-ethyl acetate present after the reaction is explained by the greater stability of the norbornyl system over the decorated cyclopentenyl system.


2-Norbornyl cation, Formation, π formation
This route is only effective if the cyclopentenyl olefin is isolated from any larger π-bonded system. The reaction rate significantly decreases if the involved double bond forms a six-membered aromatic ring as it does in 2-indanylethyl nosylate. Alkyl substitutions on the olefins have been seen to increase the reaction rate by stabilizing the resulting carbocation.


2-Norbornyl cation, Formation, Formation from rearrangement of 1-norbornyl and 7-norbornyl cations
The 2-norbornyl cation can also be formed via rearrangements of similar ions, such as the 1-norbornyl and 7-norbornyl cations, though these are generally not as well understood. Carbon-14 radioactive isotope labeling experiments have shown that complex scrambling in norbornyl cation systems allow 14C to be present at all seven positions of the norbornyl system. By cycling between low and high temperatures during the hydrolyses of 1- and 7-choloronorbornanes, a large amount of 2-norbornanol was observed in addition to the expected 1- and 7-norbornanols, respectively. Thus the 1- and 7-norbornyl cations have some mechanism by which they can rearrange to the more stable 2-norbornyl cation on the timescale of solvolysis reactions.


2-Norbornyl cation, Geometry, Spectroscopic evidence
One probe for testing whether or not the 2-norbornyl cation is non-classical is investigating the inherent symmetry of the cation. Many spectroscopic tools, such as nuclear magnetic resonance spectroscopy (NMR spectroscopy) and Raman spectroscopy, give hints about the reflectional and rotational symmetry present in a molecule or ion. Each of the three proposed structures of the 2-norbornyl cation illustrates a different molecular symmetry. The non-classical form contains a reflection plane through carbons 4, 5, 6, and the midpoint of carbons 1 and 2. The classical form contains neither reflectional nor rotational symmetry. The protonated nortricyclene structure contains a C3-symmetric rotation axis through carbon 4.


2-Norbornyl cation, Geometry, Spectroscopic evidence
Each peak in an NMR spectrum corresponds to a set of a particular element's atoms that are in similar chemical environments. The NMR spectrum of the antimony chloropentafluoride salt of the 2-norbornyl cation is not helpful at room temperature because hydride shifts occur faster than the timescale of an NMR experiment; most of the hydrogens are thus seen as equivalent and are accounted for in the same absorption peak. By lowering the temperature of the NMR experiment to −60 °C, hydride shifts are "frozen out" and more structural information can be gleaned from the spectrum. Researchers found that at these low temperatures, the 1H NMR spectrum matched what would be expected for the non-classical structure of the ion.


2-Norbornyl cation, Geometry, Spectroscopic evidence
1H and 13C NMR studies were able to confirm that any proposed Wagner-Meerwein rearrangements occurred faster than the timescale of the NMR experiment, even at low temperatures. For molecules in static equilibrium with respect to rearrangements, NMR reveals how many sets of symmetry-related nuclei are in the molecule and how many nuclei each of these sets accounts for via spectrum integration. For molecules in dynamic equilibrium such as the 2-norbornyl cation, nuclei within each set can also be transformed to one another through rearrangements with fast reaction rates.


2-Norbornyl cation, Geometry, Spectroscopic evidence
Since the proposed dynamic equilibrium of the classical ion proponents had very fast rates of rearrangement, the first NMR studies did not favor nor invalidate any of the three proposed structures. But by using solid-state NMR analysis, one can lower the temperature of the NMR experiment to 5 kelvins (−268 °C) and thus significantly slow down any rearrangement phenomena. Solid-state 13C NMR spectra of the 2-norbornyl cation shows that carbons 1 and 2 are in identical chemical environments, which is consistent only with the non-classical picture of the 2-norbornyl cation.


2-Norbornyl cation, Geometry, Spectroscopic evidence
Raman spectra of the 2-norbornyl cation show a more symmetric species than would be expected for a pair of rapidly equilibrating classical ions. Since the proposed reaction rates for the classical ion rearrangements are slower than the Raman timescale, one would expect the Raman spectra to indicate a less symmetric species if the classical picture were correct.


2-Norbornyl cation, Geometry, Spectroscopic evidence
Some studies of the 13C NMR in particular favored interpretation via the protonated nortricyclene structure. In addition, Raman spectra of the 2-norbornyl cation in some acidic solvents show an absorption band at 3110 cm-1 indicative of an electron-depleted cyclopropane ring. Since that absorption band would be expected in the C3-symmetric protonated nortricyclene, some scientists claimed this as convincing evidence for this interpretation. Other chemists have postulated that the properties of the 2-norbornyl cation are very dependent on the solvent environment. Though the high acidity and low nucleophilicity of the solvents used in aforementioned experiments may cause the protonated nortricylconium geometry to be the most stable, this geometry need not be the most energetically favorable in other solvents.


2-Norbornyl cation, Geometry, Calculations
Many calculational studies have been used to compare the feasibility of different proposed geometries. Using the quantum semi-empirical method of MINDO/3, researchers were not able to conclude which geometry of the 2-norbornyl cation was most energetically favorable. However, the classical structure was found to be the only potential minimum for the alkyl-substituted 2-methyl-2-norbornyl cation. Additional calculations using Extended Hückel Theory for Molecular Orbitals were found to favor the non-classical geometry of the cation with reflectional symmetry.


2-Norbornyl cation, Thermodynamics
Some studies have used interesting comparisons in order to probe the energetic stability of the 2-norbornyl cation provided by its delocalized nature. Comparing the rearrangement between the 3-methyl-2-norbornyl cation and the 2-methyl-2-norbornyl cation to that between the tertiary and secondary isopentane carbocations, one finds that the change in enthalpy is about 6 kcal/mol less for the norbornyl system. Since the major difference between these two reversible rearrangements is the amount of delocalization possible in the electronic ground state, one can attribute the stabilization of the 3-methyl-2-norbornyl cation to its non-classical nature. However, some experimental studies failed to observe this stabilization in solvolysis reactions.


2-Norbornyl cation, Thermodynamics
Other studies on the stability of the 2-norbornyl cation have shown that the alkyl substitutions at carbon 1 or 2 force the system to be decidedly classical. Tertiary carbocations are much more stable than their secondary counterparts and therefore do not need to adopt delocalized bonding in order to reach the lowest possible potential energy.


2-Norbornyl cation, Kinetics
To back up their suggestion of the non-classical nature of the 2-norbornyl cation, Winstein and Trifan first used kinetic evidence of the increased reaction rate for formation of the 2-exo-norbornyl cation over the 2-endo-norbornyl cation. Other researchers investigated the reaction rate of compounds that could feature anchimeric assistance but could not undergo rearrangements as the norbornyl system could show similar trends in rate enhancement. This has been claimed by some to be definitive evidence for the non-classical picture. But not all agree. Other researchers found that cyclopentane derivatives that were structurally similar to the norbornyl system still featured enhanced reaction rates, leading them to claim that the classical norbornyl cation describes the system much better.


2-Norbornyl cation, Isotope labeling experiments
Radioactive isotope labeling experiments provide a powerful tool for determining the structure of organic molecules. By systematically decomposing the 2-norbornyl cation and analyzing the amount of radioactive isotope in each decomposition product, researchers were able to show further evidence for the non-classical picture of delocalized bonding (see Figure 9). Proponents of the nonclassical picture would expect 50% of the generated CO2 in the decomposition in Figure 9 to contain 14C, while proponents of the classical picture would expect more of the generated CO2 to be radioactive due to the short-lived nature of the cation. 40% of the carbon dioxide produced via decomposition has been observed to be radioactive, suggesting that the non-classical picture is more correct.


2-Norbornyl cation, Isotope labeling experiments
Further distinction between non-classical and classical structures of the 2-norbornyl cation is possible by combining NMR experiments with isotope-labeling experiments. Isotopic substitution of one of two deuterium atoms for a hydrogen atom causes the environment of nearby NMR-active atoms to change dramatically.


2-Norbornyl cation, Isotope labeling experiments
Asymmetric deuterium isotope labeling (substitution) will cause a set of carbons that were all equivalent in the all-hydrogen species to be split into two or more sets of equivalent carbons in the deutero-labeled species; this will be manifested in the NMR spectrum as one peak in the all-hydrogen species' spectrum becoming at least two "split" peaks in the deutero-labeled species. If a system is undergoing a rapid equilibrium at a rate faster than the timescale of a 13C NMR experiment, the relevant peak will be split dramatically (on the order of 10-100 ppm).


2-Norbornyl cation, Isotope labeling experiments
If the system is instead static, the peak will be split very little. The 13C NMR spectrum of the 2-norbornyl cation at -150 °C shows that the peaks corresponding to carbons 1 and 2 are split by less than 10 ppm (parts per million) when this experiment is carried out, indicating that the system is not undergoing a rapid equilibrium as in the classical picture.


2-Norbornyl cation, X-ray crystallography
Though characterization of 2-norbornyl cation crystals may have significantly precluded further debates about its electronic structure, it does not crystallize under any standard conditions. Recently, the crystal structure has been obtained and reported through a creative means: addition of aluminum tribromide to 2-norbornyl bromide in dibromomethane at low temperatures afforded crystals of [C7H11]+[Al2Br7]−·CH2Br2. By examining the resulting crystal structure, researchers were able to confirm that the crystalline geometry best supports the case for delocalized bonding in the stable 2-norbornyl cation.


2-Norbornyl cation, X-ray crystallography
Bond lengths between the "bridging" carbon 6 and each of carbons 1 and 2 were found to be slightly longer than typical alkane bonds. According to the nonclassical picture, one would expect a bond order between 0 and 1 for these bonds, signifying that this explains the crystal structure well. The bond length between carbons 1 and 2 was reported as being between typical single and double carbon-carbon bond lengths, which agrees with nonclassical predictions of a bond order slightly above 1. According to the non-classical picture, one would expect a bond order between 0 and 1 for the first two bonds. Investigators who crystallized the 2-norbornyl cation commented that the cation proved impossible to crystallize unless provided a chemical environment that locked it into one definite orientation.


2-OH-NPA
2-OH-NPA is a drug used in scientific research which acts as a potent and selective agonist for the dopamine D2 receptor.


2-Octanol
2-Octanol (octan-2-ol, 2-OH) is a fatty alcohol. It is a secondary eight-carbon chiral compound. 2-Octanol is a colorless liquid that is poorly soluble in water but soluble in most organic solvents. 2-Octanol can be a biobased alternative of 2-ethylhexanol and its derivates in numerous applications.


2-Octanol, Manufacturing
Cleavage of ricinoleic acid produces a mixture of 2-octanol and sebacic acid ((CH2)8(CO2H)2).


2-Octanol, Uses
It can also be used as a chemical intermediate for production of various other chemicals:


2-Octyl cyanoacrylate
2-Octyl cyanoacrylate is a cyanoacrylate ester typically used as a wound closure adhesive (under the brand name Dermabond). It is closely related to octyl cyanoacrylate.


2-Octyne
2-Octyne, also known as methylpentylethin and oct-2-yne, is a type of alkyne with a triple bond at its second carbon (the '2-' indicates the location of the triple bond in the chain). Its formula is C8H14. Its density at 25 °C and otherwise stable conditions is 0.759 g/ml. The boiling point is 137 °C. The average molar mass is 110.20 g/mol.


2-Oleoylglycerol
2-Oleoylglycerol (2OG) is a monoacylglycerol that is found in biologic tissues. Its synthesis is derived from diacylglycerol precursors. It is metabolized to oleic acid and glycerol primarily by the enzyme monoacylglycerol lipase (MAGL). In 2011, 2OG was found to be an endogenous ligand to GPR119. 2OG has been shown to increase glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) levels following administration to the small intestine.


2-Oxazolidone
2-Oxazolidone is a heterocyclic organic compound containing both nitrogen and oxygen in a 5-membered ring.


2-Oxazolidone, Oxazolidinones, Evans auxiliaries
Oxazolidinones are a class of compounds containing 2-oxazolidone in the structure. In chemistry, they are useful as Evans auxiliaries, which are used for chiral synthesis. Usually, the acid chloride substrate reacts with the oxazolidinone to form an imide. Substituents at the 4 and 5 position of the oxazolidinone direct any aldol reaction to the alpha position of the carbonyl of the substrate.


2-Oxazolidone, Oxazolidinones, Pharmaceuticals
Oxazolidinones are mainly used as antimicrobials. The antibacterial effect of oxazolidinones is by working as protein synthesis inhibitors, targeting an early step involving the binding of N-formylmethionyl-tRNA to the ribosome. (See Linezolid#Mechanism of action)


2-Oxazolidone, Oxazolidinones, Pharmaceuticals, History
The first ever used oxazolidinone was cycloserine (4-amino-1,2-oxazolidin-3-one), a second line drug against tuberculosis since 1956.


2-Oxazolidone, Oxazolidinones, Pharmaceuticals, History
Developed during the nineties when several bacterial strains were becoming resistant against such antibiotics as vancomycin. Linezolid (Zyvox) is the first approved agent in the class (FDA approval April 2000).


2-Oxazolidone, Oxazolidinones, Pharmaceuticals, History
The first commercially available 1,3-oxazolidinone antibiotic was linezolid, discovered and developed by Pharmacia & Upjohn.


2-Oxazolidone, Oxazolidinones, Pharmaceuticals, History
In 2002 AstraZeneca began investigating posizolid, which is in clinical trials for use in humans.


2-Oxo-PCE
2-Oxo-PCE (also known as N-ethyldeschloroketamine, eticyclidone and O-PCE) is a dissociative anesthetic of the arylcyclohexylamine class that is closely related to deschloroketamine and eticyclidine, and has been sold online as a designer drug.


2-Oxohistidine
2-Oxohistidine is a form of histidine damaged by reactive oxygen species. It can serve as a biological marker for assessing protein modifications from oxidative stress.


2-Oxopent-4-enoic acid
2-Oxopent-4-enoic acid (2-oxopent-4-enoate) is formed by the dehydration of 4-hydroxy-2-oxopentanoate by 2-oxopent-4-enoate hydratase or by the hydrolysis of 2-hydroxymuconate semialdehyde by 2-hydroxymuconate-semialdehyde hydrolase.


2-Oxoquazepam
2-Oxoquazepam (Sch 15725) is a benzodiazepine derivative and one of the major active metabolites of quazepam (Doral).


2-Pentanol
2-Pentanol (IUPAC name: pentan-2-ol; also called sec-amyl alcohol) is an organic chemical compound. It is used as a solvent and an intermediate in the manufacturing of other chemicals. 2-Pentanol is a component of many mixtures of amyl alcohols sold industrially. 2-Pentanol is chiral and thus can be obtained as either of two stereoisomers designated as (R)-(−)-2-pentanol and (S)-(+)-2-pentanol.


2-Pentanol
2-Pentanol has been detected in fresh bananas by gas chromatography–mass spectrometry, at an abundance of 14.26±2.63 ppm.


2-Pentanone
2-Pentanone or methyl propyl ketone (MPK) is a ketone and solvent of minor importance. It is comparable to methyl ethyl ketone, but has a lower solvency and is more expensive. It occurs naturally in Nicotiana tabacum (Tobacco) and blue cheese as a metabolic product of Penicillium mold growth.


2-Pentyne
2-Pentyne, an organic compound, is an internal alkyne. It is an isomer of 1-pentyne, a terminal alkyne.


2-Pentyne, Synthesis
2-Pentyne can be synthesized by the rearrangement 1-pentyne in a solution of ethanolic potassium hydroxide or NaNH2/NH3.


2-Phenethyl propionate
2-Phenethyl propionate, also known as phenethyl propanoate or phenylethyl propionate, is the ester of phenethyl alcohol and propionic acid. It can be found in peanuts.


2-Phenethyl propionate
It has shown antifungal activity and was tested as a pesticide. It is used in some preparations used in the management of bed bugs and in other pesticide products. In the U.S it is considered a "minimal risk pesticide" and can be used as a pesticide without any registration.


2-Phenyl-3,6-dimethylmorpholine
2-Phenyl-3,6-dimethylmorpholine is a drug with stimulant and anorectic effects, related to phenmetrazine. Based on what is known from other phenylmorpholines with similar structure, it likely acts as a serotonin reuptake inhibitor and may produce antidepressant-like effects. Anecdotal reports suggest, however, that the compound is inactive aside from anorectic effects.


2-Phenyl-3-aminobutane
2-Phenyl-3-aminobutane (also known as β-methylamphetamine) is a stimulant of the phenethylamine class that is closely related to its α-methyl analog Pentorex. It was first synthesized by the German scientists Felix Haffner and Fritz Sommer in 1939 as a stimulant with milder effects, shorter duration, lower toxicity and fewer side effects compared to previously known drugs such as amphetamine.


2-Phenyl-3-aminobutane
2-Phenyl-3-aminobutane is banned in some countries as a structural isomer of methamphetamine.


2-Phenylethyl bromide
2-Phenylethyl bromide is an organobromide with the formula C6H5CH2CH2Br. It is a colorless liquid, although older samples appear yellow. Analogous to the preparation of most 1-bromoalkanes, it is prepared by free-radical addition of hydrogen bromide to styrene. These conditions lead to anti-Markovnikov addition, giving the 1-bromo derivatives.


2-Phenylhexane
2-Phenylhexane is an aromatic hydrocarbon. It can be produced by a Friedel-Crafts alkylation between 1-chlorohexane and benzene., or by the reaction of benzene and 1-hexene with various acid catalysts such as antimony pentafluoride, scandium(III) triflate, and phosphoric acid.


2-Phenylindole
2-Phenylindole is an organic compound. It is the parent structure of a group of nonsteroidal selective estrogen receptor modulators (SERMs) that includes zindoxifene, bazedoxifene, and pipendoxifene, as well as the nonsteroidal estrogen D-15414 (the major metabolite of zindoxifene).


2-Phenylphenol
2-Phenylphenol, or o-phenylphenol, is an organic compound. In terms of structure, it is one of the monohydroxylated isomers of biphenyl. It is a white solid. It is a biocide used as a preservative with E number E231 and under the trade names Dowicide, Torsite, Fungal, Preventol, Nipacide and many others.


2-Phenylphenol, Uses
The primary use of 2-phenylphenol is as an agricultural fungicide. It is generally applied post-harvest. It is a fungicide used for waxing citrus fruits. It is no longer a permitted food additive in the European Union, but is still allowed as a post-harvest treatment in 4 EU countries.


2-Phenylphenol, Uses
It is also used for disinfection of seed boxes. It is a general surface disinfectant, used in households, hospitals, nursing homes, farms, laundries, barber shops, and food processing plants. It can be used on fibers and other materials. It is used to disinfect hospital and veterinary equipment. Other uses are in rubber industry and as a laboratory reagent. It is also used in the manufacture of other fungicides, dye stuffs, resins and rubber chemicals.


2-Phenylphenol, Uses
2-Phenylphenol is found in low concentrations in some household products such as spray disinfectants and aerosol or spray underarm deodorants.


2-Phenylphenol, Uses
The sodium salt of orthophenyl phenol, sodium orthophenyl phenol, is a preservative, used to treat the surface of citrus fruits.


2-Phenylphenol, Uses
Orthophenyl phenol is also used as a fungicide in food packaging and may migrate into the contents.


2-Phenylphenol, Preparation
It is prepared by condensation of cyclohexanone to give cyclohexenylcyclohexanone. The latter undergoes dehydrogenation to give 2-phenylphenol.


2-Phenylpyridine
2-Phenylpyridine is an organic compound with the formula C6H5C5H4N (or C11H9N). It is a colourless viscous liquid. The compound and related derivatives have attracted interest as precursors to highly fluorescent metal complexes of possible value as organic light emitting diodes (OLEDs).


2-Phenylpyridine
The compound is prepared by the reaction of phenyl lithium with pyridine:


2-Phenylpyridine
The reaction of iridium trichloride with 2-phenylpyridine proceeds via cyclometallation to give the chloride-bridged complex:


2-Phenylpyridine
This complex can be converted to the pictured tris(cyclometallated) derivative tris(2-phenylpyridine)iridium.


2-Phospho-L-lactate guanylyltransferase
2-Phospho-L-lactate guanylyltransferase (EC , CofC, MJ0887) is an enzyme with systematic name GTP:2-phospho-L-lactate guanylyltransferase. This enzyme catalyses the following chemical reaction


2-Phospho-L-lactate guanylyltransferase
This enzyme is involved in the biosynthesis of coenzyme F420.


2-Phosphoglyceric acid
2-Phosphoglyceric acid (2PG), or 2-phosphoglycerate, is a glyceric acid which serves as the substrate in the ninth step of glycolysis. It is catalyzed by enolase into phosphoenolpyruvate (PEP), the penultimate step in the conversion of glucose to pyruvate.


2-Phosphoglyceric acid, In glycolysis
Compound  at KEGG Pathway Database. Enzyme  at KEGG Pathway Database. Compound  at KEGG Pathway Database. Enzyme  at KEGG Pathway Database. Compound  at KEGG Pathway Database.


2-Phosphoglyceric acid, In glycolysis
Click on genes, proteins and metabolites below to link to respective articles.


2-Phosphoglycolate
2-Phosphoglycolate (chemical formula C2H2O6P3-; also known as phosphoglycolate, 2-PG, or PG) is a natural metabolic product of the photorespiration process mediated by the enzyme ribulose 1,5-bisphosphate carboxylase (RuBisCo).


2-Phosphoglycolate, Synthesis
RuBisCo catalyzes the fixation of atmospheric carbon dioxide in the chloroplasts of plants. It uses ribulose 1,5-bisphosphate (RuBP) as substrate and facilitates carboxylation at the C2 carbon via an endiolate intermediate. The two three-carbon products (3-phosphoglycerate) are subsequently fed into the Calvin cycle. Atmospheric oxygen competes with this reaction. In a process called photorespiration RuBisCo can also catalyze addition of atmospheric oxygen to the C2 carbon of RuBP forming a high energy hydroperoxide intermediate that decomposes into 2-phosphoglycolate and 3-phosphoglycerate. Despite a higher energy barrier for the oxygenation reaction compared to carboxylation, photorespiration accounts for up to 25% of RuBisCo turnover in C3 plants.


2-Phosphoglycolate, Biological role
In plants, 2-phosphoglycolate has a potentially toxic effect as it inhibits a number of metabolic pathways. The activities of important enzymes in the central carbon metabolism of the chloroplast such as triose-phosphate isomerase, phosphofructokinase, or sedoheptulose 1,7-bisphosphate phosphatase show a significant decrease in the presence of 2-PG. Therefore, degradation of 2-PG during photorespiration is important for cellular homeostasis.


2-Phosphoglycolate, Biological role
Although mainly produced in plants, 2-PG also plays a role in mammalian metabolism, though the source of 2-PG in mammals remains incompletely understood. It is thought that the processing of breaks in the DNA-strand produces small amounts of 2-PG, but other processes may yield 2-PG as well. The phosphatase subunit of bisphosphoglycerate mutase, an enzyme found in red blood cells, shows an increase in activity by up three orders of magnitude in the presence of 2-PG, resulting in an increase of the oxygen affinity of hemoglobin.


2-Phosphoglycolate, Biological role
Photorespiration is the main way of chloroplasts to rid themselves of 2-PG. However, this pathway comes at a decreased return on investment ratio as 2-PG is transformed to 3-phosphoglycerate in an elaborate salvage pathway at the cost of one equivalent of NADH and ATP, respectively. In addition, this salvage pathway loses ½ equivalent of previously fixed carbon dioxide and releases ½ equivalent of toxic ammonia per molecule of 2-PG. This leads to a net loss of carbon in photorespiration, making it much less efficient than the Calvin cycle.


2-Phosphoglycolate, Biological role
However, this salvage pathway can also act as a cellular energy sink, preventing the chloroplastidal electron transport chain from over reduction. It is believed that this pathway also plays a role in improving the abiotic stress response of plants.


2-Phosphoglycolate, Agricultural significance
RuBisCo has been a potential target for bioengineers for agricultural purposes. A decrease in the oxygenation of RuBP may result in a boost in the efficiency of carbon assimilation in crops such as rice or wheat and therefore increase their net biomass production. Attempts have been made to artificially alter the protein structure of RuBisCo to enhance its catalytic turnover rate. Mutations in the L-subunit of the enzyme, for example, have been shown to increase both the catalytic turnover rate and RuBisCos affinity for carbon dioxide


2-Picolylamine
2-Picolylamine is an organic compound with the formula H2NCH2C5H4N. A colorless liquid, it is a common bidentate ligand and a precursor to more complex multidentate ligands such as tris(2-pyridylmethyl)amine. It is usually prepared by hydrogenation of 2-cyanopyridine. One such complex is Baratta's catalyst RuCl2(PPh3)2(ampy) (ampy = 2-picolylamine) for transfer hydrogenation. Salts of the complex [Fe(pyCH2NH2)3]2+ exhibit spin crossover behavior, whereby the complex switches from high to low spin configurations, depending on the temperature.


2-Picolylamine, Safety
The oral LD50 in quail is low, being 750 mg/kg.


2-Piece handicap
The 2-Piece (二枚落ち nimai-ochi) handicap in shogi has both of White's major pieces (the rook and the bishop) removed. Thus, White is left with pawns, golds, silvers, knights, and lances.


2-Piece handicap
The 2-Piece handicap is an official handicap of the Japan Shogi Association.


2-Piperidinone
2-Piperidinone (2-piperidone or δ-valerolactam) is a chemical compound classified as a lactam. It is used as an intermediate in the preparation of other chemicals.


2-Polyprenyl-6-hydroxyphenol methylase
2-polyprenyl-6-hydroxyphenol methylase (EC , ubiG (gene), ubiG methyltransferase, 2-octaprenyl-6-hydroxyphenol methylase) is an enzyme with systematic name S-adenosyl-L-methionine:3-(all-trans-polyprenyl)benzene-1,2-diol 2-O-methyltransferase. This enzyme catalyses the following chemical reaction


2-Polyprenyl-6-hydroxyphenol methylase
UbiG catalyses both methylation steps in ubiquinone biosynthesis in Escherichia coli.


2-Propanoyl-3-(4-isopropylphenyl)-tropane
2-Propanoyl-3-(4-isopropylphenyl)-tropane (WF-31, PIT) is a cocaine analogue which acts as a serotonin-norepinephrine-dopamine reuptake inhibitor (SNDRI). Research shows WF-31 to be approximately ten times more potent than cocaine at binding to the serotonin transporter and at inhibiting its reuptake.


2-Propylheptanol, Production
2-Propylheptanol is an oxo alcohol, meaning that it is produced from the hydroformylation ("oxo synthesis") of C4 alkenes followed by hydrogenation of the resulting aldehyde. The production route is similar to that for 2-Ethylhexanol.


2-Propylheptanol, Applications
Such compounds enjoy many applications, including as raw materials for plasticizers, resins, processing solvents, and precursors to detergents. Heat stabilizers manufactured for PVC compounds use similar high boiling and high molecular weight oxo-alcohols, which enhance product performance. A further application area of this C10 alcohol is for the manufacture of oleate- and palmitate-based materials used by the cosmetics industry. Due to its very limited miscibility with water, 2PH can be used as a special solvent, with potential application in life sciences. A promising application of these alcohols would be as precursors to acrylate monomers, potentially conferring enhanced flexibility.


2-Pyridone
2-Pyridone is an organic compound with the formula C5H4NH(O). It is a colourless solid. It is well known to form hydrogen bonded dimers and it is also a classic case of a compound that exists as tautomers.


2-Pyridone, Tautomerism
The second tautomer is 2-hydroxypyridine. This lactam lactim tautomerism can also be exhibited in many related compounds.


2-Pyridone, Tautomerism, Tautomerism in the solid state
The amide group can be involved in hydrogen bonding to other nitrogen- and oxygen-containing species.


2-Pyridone, Tautomerism, Tautomerism in the solid state
The predominant solid state form is 2-pyridone. This has been confirmed by X-ray crystallography which shows that the hydrogen in solid state is closer to the nitrogen than to the oxygen (because of the low electron density at the hydrogen the exact positioning is difficult), and IR-spectroscopy, which shows that the C=O longitudinal frequency is present whilst the O-H frequencies are absent.


2-Pyridone, Tautomerism, Tautomerism in solution
The determination of which of the two tautomeric forms is present in solution has been the subject of many publications. The energy difference appears to be very small and is dependent on the polarity of the solvent. Non -polar solvents favour the formation of 2-hydroxypyridine whereas polar solvents such as alcohols and water favour the formation of 2-pyridone.


2-Pyridone, Tautomerism, Tautomerism in solution
The energy difference for the two tautomers in the gas phase was measured by IR-spectroscopy to be 2.43 to 3.3 kJ/mol for the solid state and 8.95 kJ/mol and 8.83 kJ/mol  for the liquid state.


2-Pyridone, Tautomerism, Tautomerisation mechanism A
The single molecular tautomerisation has a forbidden 1-3 suprafacial transition state and therefore has a high energy barrier for this tautomerisation, which was calculated with theoretical methods to be 125 or 210 kJ/mol. The direct tautomerisation is energetically not favoured. There are other possible mechanisms for this tautomerisation.


2-Pyridone, Dimerisation
2-Pyridone and 2-hydroxypyridine can form dimers with two hydrogen bonds.


2-Pyridone, Dimerisation, Aggregation in the solid state
In the solid state the dimeric form is not present; the 2-pyridones form a helical structure over hydrogen bonds. Some substituted 2-pyridones form the dimer in solid state, for example the 5-methyl-3-carbonitrile-2-pyridone. The determination of all these structures was done by X-ray crystallography. In the solid state the hydrogen is located closer to the oxygen so it could be considered to be right to call the colourless crystals in the flask 2-pyridone.


2-Pyridone, Dimerisation, Aggregation in solution
In solution the dimeric form is present; the ratio of dimerisation is strongly dependent on the polarity of the solvent. Polar and protic solvents interact with the hydrogen bonds and more monomer is formed. Hydrophobic effects in non-polar solvents lead to a predominance of the dimer. The ratio of the tautomeric forms is also dependent on the solvent. All possible tautomers and dimers can be present and form an equilibrium, and the exact measurement of all the equilibrium constants in the system is extremely difficult.