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Strontium oxalate is a compound with the chemical formula . Strontium oxalate can exist either in a hydrated form () or as the acidic salt of strontium oxalate (). | 1 | Inorganic Reactions + Inorganic Compounds |
Using the appropriate reagent and conditions, alkyl, alkenyl, allylic, and α-keto sulfones may be reduced in good yield and high stereoselectivity (where applicable). Appropriate conditions for the reduction of these classes of sulfones are discussed below.
Alkyl sulfones may be reduced with sodium or lithium in liquid ammonia; however, the strongly basic conditions of these dissolving metal reductions represent a significant disadvantage. In alcoholic solvents, magnesium metal and a catalytic amount of mercury(II) chloride may be used. A wide variety of functional groups are unaffected by these conditions, including many that are transformed by dissolving metal reductions. Reductive desulfonylation with these reagents does not occur in reactions of β-hydroxy sulfones, due to the poor leaving group ability of the hydroxyl group.
A significant issue associated with the reduction of allylic sulfones is transposition of the allylic double bond, which occurs in varying amounts during reductions by metal amalgams. and tin hydrides Palladium-catalyzed reductive desulfonylations of allylic sulfones do not have this issue, and afford allylic sulfones with high site and stereoselectivity.
Aluminum amalgam (Al/Hg) may be used for the chemoselective reduction of α-sulfonylated carbonyl groups. Carboxylic acid derivatives, acetals, thioacetals, amines, alcohols, and isolated double bonds are all inert to Al/Hg. Selective desulfonylation may be carried out on β-hydroxy sulfones without reductive elimination.
Transition metal catalysis is also useful for the stereospecific reduction of alkenyl sulfones. In the presence of an excess of a Grignard reagent, a palladium(II) or nickel(II) catalyst, and a phosphorus or nitrogen ligand, alkenyl sulfones are converted to the corresponding alkenes stereospecifically in good yield. On the other hand, dissolving metal and metal amalgam reductions are not stereoselective in general. Palladium catalysis is generally superior to nickel catalysis, giving higher yields and stereoselectivities.
Alkyl and alkenyl sulfones with good leaving groups in the β position undergo elimination under reductive conditions to afford alkenes or alkynes. The Julia olefination exploits this process for the synthesis of alkenes from alkyl sulfones and carbonyl compounds. Addition of an α-sulfonyl anion to a carbonyl compound, followed by quenching with an acyl or sulfonyl chloride, leads to a β-acyloxy or -sulfonyloxy sulfone, which undergoes elimination under reductive conditions. Sodium amalgam may be used to accomplish the elimination step; however, the combination of samarium(II) iodide and HMPA is milder than strongly basic sodium amalgam and leads to higher yields in reductive elimination processes. | 0 | Organic Reactions |
It is disputed that Wöhlers synthesis sparked the downfall of the theory of vitalism, which states that organic matter possessed a certain vital force' common to all living things. Prior to the Wöhler synthesis, the work of John Dalton and Jöns Jacob Berzelius had already convinced chemists that organic and inorganic matter obey the same chemical laws. It took until 1845 when Kolbe reported another inorganic – organic conversion (of carbon disulfide to acetic acid) before vitalism started to lose support. Wöhler also did not, as some textbooks have claimed, act as a "crusader" against vitalism. A 2000 survey by historian Peter Ramberg found that 90% of chemical textbooks repeat some version of the Wöhler myth. | 0 | Organic Reactions |
In free-radical chain-growth polymerization, chain termination can occur by a disproportionation step in which a hydrogen atom is transferred from one growing chain molecule to another one, which produces two dead (non-growing) chains.
:: Chain—CH–CHX + Chain—CH–CHX → Chain—CH=CHX + Chain—CH–CHX
in which, Chain— represents the already formed polymer chain, and indicates a reactive free radical. | 0 | Organic Reactions |
Elaidinization of oleic acid, a common component of vegetable oils, yields its trans-isomer elaidic acid. | 0 | Organic Reactions |
Lanthanum acetate is used in specialty glass manufacturing and in water treatment.
Also, it is used to produce porous lanthanum oxyfluoride (LaOF) films.
It is also used as a component in the production of ceramic products and as a catalyst in the pharmaceutical industry. | 1 | Inorganic Reactions + Inorganic Compounds |
In organic chemistry, ketonic decarboxylation (also known as decarboxylative ketonization) is a type of organic reaction and a decarboxylation converting two equivalents of a carboxylic acid () to a symmetric ketone () by the application of heat. It can be thought of as a decarboxylative Claisen condensation of two identical molecules. Water and carbon dioxide are byproducts:
Bases promote this reaction. The reaction mechanism likely involves nucleophilic attack of the alpha-carbon of one acid group on the other acid groups carbonyl (), possibly as a concerted reaction with the decarboxylation. The initial formation of an intermediate carbanion via decarboxylation of one of the acid groups prior to the nucleophilic attack has been proposed, but is unlikely since the byproduct resulting from the carbanions protonation by the acid has never been reported. This reaction is different from oxidative decarboxylation, which proceeds through a radical mechanism and is characterised by a different product distribution in isotopic labeling experiments with two different carboxylic acids. With two different carboxylic acids, the reaction behaves poorly because of poor selectivity except when one of the acids (for example, a small, volatile one) is used in large excess. | 0 | Organic Reactions |
A wide variety of divinylcyclopropanes undergo the titular reaction. These precursors have been generated by a variety of methods, including the addition of cyclopropyl nucleophiles (salts of lithium, or copper) to activated double or triple bonds, elimination of bis(2-haloethyl)cyclopropanes and cyclopropanation.
In the example below, cuprate addition-elimination generates the transient enone 1, which rearranges to spirocycle 2.
Organolithiums can be employed in a similar role, but add in a direct fashion to carbonyls. Products with fused topology result.
Rearrangement after elimination of ditosylates has been observed; the chlorinated cycloheptadiene thus produced isomerizes to conjugated heptadiene 3 during the reaction.
Cyclopropanation with conjugated diazo compounds produces divinylcyclopropanes that then undergo rearrangement. When cyclic starting materials are used, bridged products result.
Substrates containing three-membered heterocyclic rings can also undergo the reaction. cis-Divinylepoxides give oxepines at elevated temperatures (100 °C). trans Isomers undergo an interesting competitive rearrangement to dihydrofurans through the intermediacy of a carbonyl ylide and the same ylide intermediate has been proposed as the direct precursor to the oxepine product 4. Conjugated dienyl epoxides form similar products, lending support to the existence of an ylide intermediate.
Divinyl aziridines undergo a similar suite of reactions providing azepines or vinyl pyrrolines depending on the relative configuration of the aziridine starting material. Divinyl thiiranes can provide thiepines or dihydrothiophenes, although these reactions are slower than those of the corresponding nitrogen- and oxygen-containing compounds. | 0 | Organic Reactions |
The valence electrons of this compound match those of nitric oxide. Sulfur mononitride can be described as some average of a set of resonance structures. The singly bonded structure (first resonance structure shown) has little contribution. The formal bond order is considered to be 2.5. | 1 | Inorganic Reactions + Inorganic Compounds |
Heating hexachlorophosphazene to ca. 250 °C induces polymerisation. The tetramer also polymerises in this manner, although more slowly. The conversion is a type of ring-opening polymerisation (ROP). The ROP mechanism is found to be catalysed by Lewis acids, but is overall not very well understood. Prolonged heating of the polymer at higher temperatures (ca. 350 °C) will cause depolymerisation.
The structure of the inorganic chloropolymer product (polydichlorophosphazene) comprises a linear – chain, where n ~ 15000. It was first observed in the late 19th century and its form after chain cross-linking has been called "inorganic rubber" due to its elastomeric behaviour.
This polydichlorophosphazene product is the starting material for a wide class of polymeric compounds, collectively known as polyphosphazenes. Substitution of the chloride groups by other nucleophilic groups, especially alkoxides as laid out above, yields numerous characterised derivatives. | 1 | Inorganic Reactions + Inorganic Compounds |
Forgione, P., Bilodeau, F. et al. reported that heteroatoms containing a carboxylic acid also are tolerated by palladium monometallic systems and undergo decarboxylative cross coupling with aryl halides. In the proposed mechanism the initial step is oxidative addition of the aryl halide forming an aryl–palladium intermediate. Electrophilic palladation then occurs at carbon-3 of the heteroatom. From this intermediate there are two possible pathways for the cycle to continue on. The first is palladium migration from carbon-3 to carbon-2 along with the expulsion of carbon dioxide. This forms the aryl–palladium–heteroatom intermediate, which undergoes reductive elimination to form the final heteroaromatic compound. The second pathway only occurs when R is a proton. If this is the case, deprotonation occurs to regain aromaticity of the heteroatom. This intermediate then undergoes reductive elimination, coupling the aryl to the carbon-3 position of the heteroatom. As this compound still contains the carboxylic acid it is then free to re enter the catalytic cycle where it undergoes coupling at the carbon 2 position, along with the expulsion of carbon dioxide to form a biaryl heteroatom. As this pathway competes with the decarboxylation step, two products are formed making this reaction less selective. As a result, heteroatoms, which are substituted at the carbon 3 position and are more favored due to the higher level of control they provide. | 0 | Organic Reactions |
The first disproportionation reaction to be studied in detail was:
This was examined using tartrates by Johan Gadolin in 1788. In the Swedish version of his paper he called it . | 0 | Organic Reactions |
Reductive desulfonylation reactions lead to the replacement of a carbon-sulfur bond in the sulfonyl group with a carbon-hydrogen bond. Because the sulfonyl group is by definition attached to two carbons, however, reduction to two sets of products is possible. Mechanistic studies of reductions employing metal amalgams as the reducing agent suggest that upon electron transfer to the sulfone, fragmentation to a sulfinate anion and the more stable organic radical occurs. Immediate reduction of the radical and protonation then occur to afford the sulfur-free product derived from the more stable radical. Thus, S-alkyl bonds are cleaved in preference to S-aryl or S-alkenyl bonds.
Samarium(II) iodide may be used to reductively cleave α-keto sulfones; in the presence of hexamethylphosphoramide (HMPA), SmI is able to effect reductive elimination of α-functionalized sulfones (see equation () below).
Tin hydrides reduce α-keto and allylic sulfones. The mechanisms of these processes involve the addition of a tin-centered radical to the substrate followed by elimination of a sulfinyl radical, which abstracts a hydrogen from a molecule of tin hydride to propagate the radical chain. Protonation of the organotin intermediates thus formed (by sulfinic acid generated in situ) leads to reduced products. Addition of a stoichiometric amount of proton source allows the use of tin hydride in catalytic amounts. Although desulfonylations of allylic sulfones are site selective (providing only products of allylic transposition), they are not stereoselective and afford mixtures of double bond isomers. The mechanism of desulfonylation of α-keto sulfones is similar.
Transition-metal-mediated reductive desulfonylations rely on the generation of an intermediate π-allyl complex, which undergoes nucleophilic attack by hydride or another nucleophile to afford reduced products. Nucleophilic attack generally occurs at the less substituted position of the π-allyl moiety, although site selectivity depends strongly on the substrate and reaction conditions. Palladium(0) complexes are the most commonly used precatalysts. | 0 | Organic Reactions |
The halogens can all react with metals to form metal halides according to the following equation:
:2M + nX → 2MX
where M is the metal, X is the halogen, and MX is the metal halide.
In practice, this type of reaction may be very exothermic, hence impractical as a preparative technique. Additionally, many transition metals can adopt multiple oxidation states, which complicates matters. As the halogens are strong oxidizers, direct combination of the elements usually leads to a highly oxidized metal halide. For example, ferric chloride can be prepared thus, but ferrous chloride cannot. Heating the higher halides may produce the lower halides; this occurs by thermal decomposition or by disproportionation. For example, gold(III) chloride to gold(I) chloride:
:AuCl → AuCl + Cl at 160°C
Metal halides are also prepared by the neutralization of a metal oxide, hydroxide, or carbonate with the appropriate halogen acid. For example, with sodium hydroxide:
:NaOH + HCl → NaCl + HO
Water can sometimes be removed by heat, vacuum, or the presence of anhydrous hydrohalic acid. Anhydrous metal chlorides suitable for preparing other coordination compounds may be dehydrated by treatment with thionyl chloride:
:MCl·xHO + x SOCl → MCl + x SO + 2x HCl
The silver and thallium(I) cations have a great affinity for halide anions in solution, and the metal halide quantitatively precipitates from aqueous solution. This reaction is so reliable that silver nitrate is used to test for the presence and quantity of halide anions. The reaction of silver cations with bromide anions:
:Ag (aq) + Br (aq) → AgBr (s)
Some metal halides may be prepared by reacting oxides with halogens in the presence of carbon (carbothermal reduction): | 1 | Inorganic Reactions + Inorganic Compounds |
The thermite () reaction was discovered in 1893 and patented in 1895 by German chemist Hans Goldschmidt. Consequently, the reaction is sometimes called the "Goldschmidt reaction" or "Goldschmidt process". Goldschmidt was originally interested in producing very pure metals by avoiding the use of carbon in smelting, but he soon discovered the value of thermite in welding.
The first commercial application of thermite was the welding of tram tracks in Essen in 1899. | 1 | Inorganic Reactions + Inorganic Compounds |
*Pyrohydrolysis
**Spray roaster pyrohydrolysis
**Fluidised bed pyrohydrolysis
*Hydrothermal regeneration
*Electrolytic Fe precipitation | 1 | Inorganic Reactions + Inorganic Compounds |
Alcohols alkylate to give ethers:
When the alkylating agent is an alkyl halide, the conversion is called the Williamson ether synthesis.
Alcohols are also good alkylating agents in the presence of suitable acid catalysts. For example, most methyl amines are prepared by alkylation of ammonia with methanol. The alkylation of phenols is particularly straightforward since it is subject to fewer competing reactions.
:(with as a spectator ion)
More complex alkylation of a alcohols and phenols involve ethoxylation. Ethylene oxide is the alkylating group in this reaction. | 0 | Organic Reactions |
Burnt bones have been recovered from numerous Ancient Greek sanctuaries dating from the Late Bronze Age up to the Hellenistic period. The burnt bones are often calcined with a white or blueish color, allowing archaeologists to identify them as sacrificial remains. At the sanctuary to Artemis in Eretria a round altar of fieldstones filled with soil was found, dating to the 8th century BC. The upper surface was covered with clay and animal bones were burned on top, then apparently swept off the surface with terracotta, metal objects, and pottery and trampled until the altar was eventually subsumed by the ritual debris. Some scholars have attributed these altars to chthonian rituals, but this is disputed. Xenocrates of Aphrodisias reported its use as a medicinal ingredient, although cannibalism was, according to Galen, prohibited under the laws of the Roman Empire. | 1 | Inorganic Reactions + Inorganic Compounds |
Prior to the introduction of diethylaminosulfur trifluoride (DAST) in 1970 for the replacement of hydroxyl groups with fluoride, sulfur tetrafluoride was the reagent most commonly used to accomplish this transformation. However, sulfur tetrafluoride only reacts with the most acidic hydroxyl groups (its substrate scope is limited), and is difficult to handle, toxic, and capable of generating hydrogen fluoride upon hydrolysis. Thus, aminosulfurane reagents such as diethylaminosulfur trifluoride have largely replaced SF as the reagents of choice for replacement of hydroxyl groups with fluoride.
Aminosulfuranes are usually prepared by reaction of the corresponding dialkylamino(trialkyl)silanes with SF. When the aminosulfurane is exposed to a second equivalent of aminosilane, bis(dialkylamino)sulfur difluorides result. Tris(dialkylamino)sulfonium difluorotrimethylsilicates such as tris(diethylamino)sulfonium difluorotrimethylsilicate (TASF) have achieved synthetic utility as reagents for the fluorination of halides. These form when three equivalents of aminosilane are exposed to sulfur tetrafluoride. | 0 | Organic Reactions |
Boric acid can be used as an antiseptic for minor burns or cuts and is sometimes used in salves and dressings, such as boracic lint. Boric acid is applied in a very dilute solution as an eye wash. Boric acid vaginal suppositories can be used for recurrent candidiasis due to non-albicans candida as a second line treatment when conventional treatment has failed. It is less effective than conventional treatment overall. Boric acid largely spares lactobacilli within the vagina. As TOL-463, it is under development as an intravaginal medication for the treatment for vulvovaginal candidiasis.
As an antibacterial compound, boric acid can also be used as an acne treatment. It is also used as prevention of athlete's foot, by inserting powder in the socks or stockings. Various preparations can be used to treat some kinds of (ear infection) in both humans and animals. The preservative in urine sample bottles in the UK is boric acid.
Boric acid solutions used as an eye wash or on abraded skin are known to be toxic, particularly to infants, especially after repeated use; this is because of its slow elimination rate.
Boric acid is one of the most commonly used substances that can counteract the harmful effects of reactive hydrofluoric acid (HF) after an accidental contact with the skin. It works by forcing the free anions into the inert tetrafluoroborate anion. This process defeats the extreme toxicity of hydrofluoric acid, particularly its ability to sequester ionic calcium from blood serum which can lead to cardiac arrest and bone decomposition; such an event can occur from just minor skin contact with HF. | 1 | Inorganic Reactions + Inorganic Compounds |
Diimide is most effective at reducing unpolarized carbon-carbon double or triple bonds. In reactions with other unsaturated systems, disproportionation of diimide to nitrogen gas and hydrazine is a competing process that significantly degrades the reducing agent. Many groups that are ordinarily sensitive to reductive conditions, including peroxides, are not affected by the conditions of diimide reductions.
Diimide will selectively reduce less substituted double bonds under some conditions. Discrimination between terminal and disubstituted double bonds is often low, however.
Allenes are reduced to the more highly substituted alkene in the presence of diimide, although yields are low.
Iodoalkynes represent an exception to the rule that alkenes cannot be obtained from alkynes. After diimide reduction of iodoalkynes, cis-iodoalkenes may be isolated in good yield.
Recently, diimide has been generated catalytically through the oxidation of hydrazine by a flavin-based organocatalyst. This system selectively reduces terminal double bonds.
In general, diimide does not efficiently reduce polarized double bonds; however, a limited number of examples do exist in the literature. Aromatic aldehydes are reduced by diimide generated through the decarboxylation of potassium azodicarboxylate. | 0 | Organic Reactions |
General Control Non-Derepressible 5 (Gcn5) –related N-Acetyltransferases (GNATs) is one of the many studied families with acetylation abilities. This superfamily includes the factors Gcn5 which is included in the SAGA, SLIK, STAGA, ADA, and A2 complexes, Gcn5L, p300/CREB-binding protein associated factor (PCAF), Elp3, HPA2 and HAT1. Major features of the GNAT family include HAT domains approximately 160 residues in length and a conserved bromodomain that has been found to be an acetyl-lysine targeting motif. Gcn5 has been shown to acetylate substrates when it is part of a complex. Recombinant Gcn5 has been found to be involved in the acetylation of the H3 histones of the nucleosome. To a lesser extent, it has been found to also acetylate H2B and H4 histones when involved with other complexes. PCAF has the ability to act as a HAT protein and acetylate histones, it can acetylate non-histone proteins related to transcription, as well as act as a coactivator in many processes including myogenesis, nuclear-receptor-mediated activation and growth-factor-signaled activation. Elp3 has the ability to acetylate all histone subunits and also shows involvement in the RNA polymerase II holoenzyme. | 0 | Organic Reactions |
Simple, unhindered dialkylboranes are reactive at room temperature towards most alkenes and terminal alkynes but are difficult to prepare in high purity, since they exist in equilibrium with mono- and trialkylboranes. One common way of preparing them is the reduction of dialkylhalogenoboranes with metal hydrides. An important synthetic application using such dialkylboranes, such as diethylborane, is the transmetallation of the organoboron compounds to form organozinc compounds. | 0 | Organic Reactions |
An annulation is defined as a transformation of one or more acyclic precursors resulting in the fusion of a new ring via two newly generated bonds. These strategies can be used to create aromatic systems from acyclic precursors in a single step, with many substituents already in place. A common synthetic annulation reaction is the Robinson annulation. It is a useful reactions for forming six-membered rings and generating polycyclic compounds. It is the combination of the Michael Addition and the Aldol Condensation reaction. | 0 | Organic Reactions |
Factors governing organic reactions are essentially the same as that of any chemical reaction. Factors specific to organic reactions are those that determine the stability of reactants and products such as conjugation, hyperconjugation and aromaticity and the presence and stability of reactive intermediates such as free radicals, carbocations and carbanions.
An organic compound may consist of many isomers. Selectivity in terms of regioselectivity, diastereoselectivity and enantioselectivity is therefore an important criterion for many organic reactions. The stereochemistry of pericyclic reactions is governed by the Woodward–Hoffmann rules and that of many elimination reactions by Zaitsev's rule.
Organic reactions are important in the production of pharmaceuticals. In a 2006 review, it was estimated that 20% of chemical conversions involved alkylations on nitrogen and oxygen atoms, another 20% involved placement and removal of protective groups, 11% involved formation of new carbon–carbon bond and 10% involved functional group interconversions. | 0 | Organic Reactions |
The metal chloride solution (in the most common case waste pickle liquor from a carbon steel pickling line) is fed to the venturi evaporator (III), where direct mass and heat exchange with the hot roast gas from the roaster (reactor/cyclone) takes place. The separator (IV) separates the gas and liquid phase of the venturi evaporator product. The liquid phase is re-circulated back to the venturi evaporator to increase mass and heat exchange performance.
* approx. 25 to 30% of the waste acid (HO, HCl) are evaporated
* roast gas is cooled down to approx. 92 to 96 °C
* dust particles are removed from the roast gas | 1 | Inorganic Reactions + Inorganic Compounds |
Cadmium sulfide has, like zinc sulfide, two crystal forms. The more stable hexagonal wurtzite structure (found in the mineral Greenockite) and the cubic zinc blende structure (found in the mineral Hawleyite). In both of these forms the cadmium and sulfur atoms are four coordinate. There is also a high pressure form with the NaCl rock salt structure.
Cadmium sulfide is a direct band gap semiconductor (gap 2.42 eV). The proximity of its band gap to visible light wavelengths gives it a coloured appearance.<br /> As well as this obvious property other properties result:
* the conductivity increases when irradiated, (leading to uses as a photoresistor)
* when combined with a p-type semiconductor it forms the core component of a photovoltaic (solar) cell and a CdS/CuS solar cell was one of the first efficient cells to be reported (1954)
* when doped with for example Cu ("activator") and Al ("coactivator") CdS luminesces under electron beam excitation (cathodoluminescence) and is used as phosphor
* both polymorphs are piezoelectric and the hexagonal is also pyroelectric
* electroluminescence
* CdS crystals can act as a gain medium in solid state laser
* In thin-film form, CdS can be combined with other layers for use in certain types of solar cells. CdS was also one of the first semiconductor materials to be used for thin-film transistors (TFTs). However interest in compound semiconductors for TFTs largely waned after the emergence of amorphous silicon technology in the late 1970s.
* Thin films of CdS can be piezoelectric and have been used as transducers which can operate at frequencies in the GHz region.
* Nanoribbons of CdS show a net cooling due annihilation of phonons, during anti-Stokes luminescence at ~510 nm. As a result, a maximum temperature drop of 40 and 15 K has been demonstrated when the nanoribbons are pumped with a 514 or 532 nm laser. | 1 | Inorganic Reactions + Inorganic Compounds |
Asymmetric hydrogenations operate by conventional mechanisms invoked for other hydrogenations. This includes inner sphere mechanisms, outer sphere mechanisms and the σ-bond metathesis mechanisms. The type of mechanism employed by a catalyst is largely dependent on the ligands used in a system, which in turn leads to certain catalyst-substrate affinities. | 0 | Organic Reactions |
The technique is applied to conversions that proceed via unimolecular pathways. 2-Acetoxydioxane, when heated at 425 °C converts to the highly reactive dioxene, via loss of acetic acid.
2-Furonitrile has been prepared by flash-dehydration of 2-furoic acid amide or oxime over molecular sieves. The strained ring benzocyclobutenone has been prepared by FVP from a simple benzoyl chloride precursor. | 0 | Organic Reactions |
Borate ions occur, alone or with other anions, in many borate and borosilicate minerals such as borax, boracite, ulexite (boronatrocalcite) and colemanite. Borates also occur in seawater, where they make an important contribution to the absorption of low frequency sound in seawater.
Borates also occur in plants, including almost all fruits. | 1 | Inorganic Reactions + Inorganic Compounds |
The first to investigate trifluoromethyl groups in relationship to biological activity was F. Lehmann in 1927. An early review appeared in 1958. An early synthetic method was developed by Frédéric Swarts in 1892, based on antimony fluoride. In this reaction benzotrichloride was reacted with SbF to form PhCFCl and
PhCF. In the 1930s Kinetic Chemicals and IG Farben replaced SbF with HF.
The McLoughlin-Thrower reaction (1968) is an early coupling reaction using iodofluoroalkanes, iodoaromatic compounds and copper. In 1969 Kobayashi & Kumadaki adapted their protocol for trifluoromethylations. | 0 | Organic Reactions |
Ortho lithiation can be used to generate many of the same structures as lateral lithiation; however, reactivity differences between aryl- and benzyllithium species may suggest the use of one method over the other. A useful alternative method for stereoselective functionalization of the benzylic position involves the use of chromium arene complexes. Substitution at the benzylic position is much better tolerated in methods that employ benzylic lithiation of chromium arene complexes than lateral lithiations; however, the chromium byproducts of these reactions pose waste disposal difficulties. The use of mixed zinc/copper organometallic reagents generated from benzyl bromides represents a second alternative to lateral lithiation. The functional group compatibility of this method is greater than lateral lithiation, but more steps are required to generate the reactive organometallic species from an unfunctionalized benzylic position. | 0 | Organic Reactions |
Alkoxyaluminium hydrides are typically prepared by treatment of lithium aluminium hydride with the corresponding alcohol. Hydrogen evolution indicates the formation of alkoxyaluminium hydride products. Hindered hydrides such as lithium tri-(tert-butoxy)aluminium hydride (LTBA) are stable for long periods of time under inert atmosphere, but lithium trimethoxyaluminium hydride (LTMA) undergoes disproportionation and should be used immediately after preparation. Pure, solid Red-Al is stable for several hours under inert atmosphere and is available commercially as a 70%-solution in toluene under the trade name Vitride or Synhydrid. | 0 | Organic Reactions |
When water is added to cement, each of the compounds undergoes hydration and contributes to the final state of the concrete. Only calcium silicates contribute to the strength. Tricalcium silicate is responsible for most of the early strength (first 7 days). Dicalcium silicate, which reacts more slowly, only contributes to late strength.
Calcium silicate hydrate (also shown as C-S-H) is a result of the reaction between the silicate phases of Portland cement and water. This reaction typically is expressed as:
also written in cement chemist notation, (CCN) as:
: 2 + 7 H → + 3 CH + heat
or, tricalcium silicate + water → calcium silicate hydrate + calcium hydroxide + heat
The stoichiometry of C-S-H in cement paste is variable and the state of chemically and physically bound water in its structure is not transparent, which is why "-" is used between C, S, and H.
Synthetic C-S-H can be prepared from the reaction of CaO and SiO in water or through the double precipitation method using various salts. These methods provide the flexibility of producing C-S-H at specific C/S (Ca/Si, or CaO/SiO) ratios. The C-S-H from cement phases can also be treated with an ammonium nitrate solution in order to induce calcium leaching, and so to achieve a given C/S ratio. | 1 | Inorganic Reactions + Inorganic Compounds |
Potassium sulfide is an inorganic compound with the formula KS. The colourless solid is rarely encountered, because it reacts readily with water, a reaction that affords potassium hydrosulfide (KSH) and potassium hydroxide (KOH). Most commonly, the term potassium sulfide refers loosely to this mixture, not the anhydrous solid. | 1 | Inorganic Reactions + Inorganic Compounds |
In comparison to cationic cyclizations, radical cyclizations avoid issues associated with Wagner-Meerwein rearrangements, do not require strongly acidic conditions, and can be kinetically controlled. Cationic cyclizations are usually thermodynamically controlled. Radical cyclizations are much faster than analogous anionic cyclizations, and avoid β-elimination side reactions. Anionic Michael-type cyclization is an alternative to radical cyclization of activated olefins. Metal-catalyzed cyclization reactions usually require mildly basic conditions, and substrates must be chosen to avoid β-hydride elimination. The primary limitation of radical cyclizations with respect to these other methods is the potential for radical side reactions. | 0 | Organic Reactions |
In asymmetric addition of dialkylzinc compounds to aldehydes dialkyl zinc compounds can be used to perform asymmetric additions to aldehydes, generating substituted alcohols as products (See Barbier reaction). Chiral alcohols are prevalent in many natural products, drugs, and other important organic molecules. Dimethyl zinc is often used with an asymmetric amino alcohol, amino thiol, or other ligand to affect enantioselective additions to aldehydes and ketones. One of the first examples of this process, reported by Noyori and colleagues, features the use of the amino alcohol ligand (−)-3-exo-dimethylaminoisobornenol along with dimethylzinc to add a methyl group asymmetrically to benzaldehyde (see figure). Many ligands have been developed for binding zinc during addition reactions. TADDOLs (tetraaryl-1,3-dioxolane-4,5-dimethanols), which are derived from chiral tartaric acid, are a class of diol ligands often used to bind titanium, but have been adopted for zinc addition chemistry. These ligands require relatively low catalyst loadings, and can achieve up to 99% ee in dialkylzinc additions to aromatic and aliphatic aldehydes. Martens and colleagues have used azetidine alcohols as ligands for asymmetric zinc additions. The researchers found that when paired with catalytic n-butyllithium, diethylzinc can add to aromatic aldehydes with ee in the range of 94-100%.
Many studies have shown that in zinc addition reactions, the enantioselectivity is not linearly correlated with catalyst enantiomeric purity. Researchers propose that this is because the kinetics of the reaction are controlled by the relative concentrations of hetero and homodimeric catalytic complexes; that is, the system displays autocatalysis because the product alcohol itself acts as an asymmetric ligand on zinc. | 0 | Organic Reactions |
A solution of the amide (0.365 g, 0.809 mmol), Pd(PPh) (0.187 g, 0.162 mmol), and triethylamine (1.12 mL, 8.08 mmol) in MeCN (8 mL) in a sealed tube was heated slowly to 120°. After stirring for 4 hours, the reaction mixture was cooled to room temperature, and the solvent was evaporated. The residue was chromatographed (loaded with CHCl) to give the title product 316 (0.270 g, 90%) as a colorless oil; R 0.42 (EtOAc/petroleum ether 10:1); [α] +14.9 (c, 1.0, CHCl); IR 3027, 2930, 1712, 1673, 1608, 1492, 1343, 1248 cm; H NMR (400 MHz) δ 7.33–7.21 (m, 6 H), 7.07 (dd, J = 7.3, 16.4 Hz, 1 H), 7.00 (t, J = 7.5 Hz, 1 H), 6.77 (d, J = 7.7 Hz, 1 H), 6.30 (dd, J = 8.7, 11.4 Hz, 1 H), 5.32 (d, J = 15.7 Hz, 1 H), 5.04 (s, 1 H), 4.95 (s, 1 H), 4.93 (d, J = 11.1 Hz, 1 H), 4.17 (s, 1 H), 3.98 (d, J = 15.7 Hz, 1 H), 3.62 (d, J = 8.7 Hz, 1 H), 3.17 (s, 3 H), 2.56 (dd, J = 3.5, 15.5 Hz, 1 H), 2.06 (dd, J = 2.8, 15.5 Hz, 1 H); C NMR (100 MHz) δ 177.4, 172.9, 147.8, 142.2, 136.5, 132.2, 131.6, 128.8, 128.4, 128.2, 127.7, 127.1, 123.7, 122.9, 107.9, 105.9, 61.0, 54.7, 49.9, 44.4, 38.2, 26.4; HRMS Calcd. for CHNO: 370.1681. Found: 370.1692. | 0 | Organic Reactions |
Sodium borohydride and lithium aluminium hydride are commonly used for the reduction of organic compounds. These two reagents are on the extremes of reactivity—whereas lithium aluminium hydride reacts with nearly all reducible functional groups, sodium borohydride reacts with a much more limited range of functional groups. Diminished or enhanced reactivity may be realized by the replacement of one or more of the hydrogens in these reagents with alkoxy groups.
Additionally, substitution of hydrogen for chiral alkoxy groups in these reagents enables asymmetric reductions. Although methods involving stoichiometric amounts of chiral metal hydrides have been supplanted in modern times by enantioselective catalytic reductions, they are of historical interest as early examples of stereoselective reactions.
The table below summarizes the reductions that may be carried out with a variety of metal aluminium hydrides and borohydrides. The symbol "+" indicates that reduction does occur, "-" indicates that reduction does not occur, "±" indicates that reduction depends on the structure of the substrate, and "0" indicates a lack of literature information. | 0 | Organic Reactions |
Histone acetylation and deacetylation are the processes by which the lysine residues within the N-terminal tail protruding from the histone core of the nucleosome are acetylated and deacetylated as part of gene regulation.
Histone acetylation and deacetylation are essential parts of gene regulation. These reactions are typically catalysed by enzymes with "histone acetyltransferase" (HAT) or "histone deacetylase" (HDAC) activity. Acetylation is the process where an acetyl functional group is transferred from one molecule (in this case, acetyl coenzyme A) to another. Deacetylation is simply the reverse reaction where an acetyl group is removed from a molecule.
Acetylated histones, octameric proteins that organize chromatin into nucleosomes, the basic structural unit of the chromosomes and ultimately higher order structures, represent a type of epigenetic marker within chromatin. Acetylation removes the positive charge on the histones, thereby decreasing the interaction of the N termini of histones with the negatively charged phosphate groups of DNA. As a consequence, the condensed chromatin is transformed into a more relaxed structure that is associated with greater levels of gene transcription. This relaxation can be reversed by deacetylation catalyzed by HDAC activity. Relaxed, transcriptionally active DNA is referred to as euchromatin. More condensed (tightly packed) DNA is referred to as heterochromatin. Condensation can be brought about by processes including deacetylation and methylation. | 0 | Organic Reactions |
Metal–inorganic frameworks (MIFs) are a class of compounds consisting of metal ions or clusters coordinated to inorganic ligands to form one-, two-, or three-dimensional structures. They are a subclass of coordination polymers, with the special feature that they are often porous. They are inorganic counterpart of Metal–organic frameworks.
__TOC__ | 1 | Inorganic Reactions + Inorganic Compounds |
The WGS reaction is used in combination with the solid adsorption of CO in the sorption enhanced water gas shift (SEWGS) in order to produce a high pressure hydrogen stream from syngas. | 1 | Inorganic Reactions + Inorganic Compounds |
It has been reported that mammalian glycosylation can improve the therapeutic efficacy of biotherapeutics. For example, therapeutic efficacy of recombinant human interferon gamma, expressed in HEK 293 platform, was improved against drug-resistant ovarian cancer cell lines. | 0 | Organic Reactions |
The reaction mechanism involves the formation of a positively charged halonium ion in a molecule that also contains a carboxylic acid (or other functional group that is a precursor to it). The oxygen of the carboxyl acts as a nucleophile, attacking to open the halonium ring and instead form a lactone ring. The reaction is usually performed under mildly basic conditions to increase the nucleophilicity of the carboxyl group. | 0 | Organic Reactions |
The chelation of lithium cation with the methoxy group is one of the most important features of the transition state for Enders hydrazone alkylation reaction. It is necessary to have this chelation effect to achieve high stereoselectivity. The development and modification of Enders hydrazone alkylation reaction mainly focus on the addition of more steric hindrance on the pyrrolidine rings of both SAMP and RAMP, while preserving the methoxy group for lithium chelation.
The most famous four variants of SAMP and RAMP are SADP, SAEP, SAPP and RAMBO, whose structures are shown below.
In 2011, several N-amino cyclic carbamates were synthesized and studied for asymmetric hydrazone alkylation reactions. Both the stereochemistry and regioselectivity of the reactions turned out to be very promising. These new compounds consist of a new class of chiral auxiliary based on the carbamate structure and, therefore, no longer belong to the family of SAMP and RAMP. But they do provide very powerful alternatives to the traditional pyrrolidine systems. | 0 | Organic Reactions |
;Aldehydes and ketones
Polymeric hydrosilanes, such as polymethylhydrosiloxane (PHMS), may be employed to facilitate separation of the reduced products from silicon-containing byproducts.
Enantioselective reductions of ketones may be accomplished through the use of catalytic amounts of chiral transition metal complexes. In some cases, the transition metal simply serves as a Lewis acid that coordinates to the ketone oxygen; however, some metals (most notably copper) react with hydrosilanes to afford metal hydride intermediates, which act as the active reducing agent.
In the presence of rhodium catalyst 1 and rhodium trichloride, 2-phenylcyclohexanone is reduced with no diastereoselectivity but high enantioselectivity.
;Esters
Esters may be reduced to alcohols under conditions of nucleophilic activation with caesium or potassium fluoride.
Aldehydes undergo hydrosilylation in the presence of hydrosilanes and fluoride. The resulting silyl ethers can be hydrolyzed with 1 M hydrochloric acid. Optimal yields of the hydrosilylation are obtained when the reaction is carried out in very polar solvents. | 0 | Organic Reactions |
Examples of photochemical reactions are those between certain arenes and alkenes forming [2+2] and [2+4] cycloaddition adducts. | 0 | Organic Reactions |
Biofuels that are produced through hydrothermal liquefaction are carbon neutral, meaning that there are no net carbon emissions produced when burning the biofuel. The plant materials used to produce bio-oils use photosynthesis to grow, and as such consume carbon dioxide from the atmosphere. The burning of the biofuels produced releases carbon dioxide into the atmosphere, but is nearly completely offset by the carbon dioxide consumed from growing the plants, resulting in a release of only 15-18 g of CO per kWh of energy produced. This is substantially lower than the releases rate of fossil fuel technologies, which can range from releases of 955 g/kWh (coal), 813 g/kWh (oil), and 446 g/kWh (natural gas). Recently, Steeper Energy announced that the carbon intensity (CI) of its Hydrofaction™ oil is 15 COeq/MJ according to [http://www.ghgenius.ca/ GHGenius model] (version 4.03a), while diesel fuel is 93.55 COeq/MJ.
Hydrothermal liquefaction is a clean process that doesn't produce harmful compounds, such as ammonia, NO, or SO. Instead the heteroatoms, including nitrogen, sulfur, and chlorine, are converted into harmless byproducts such as N and inorganic acids that can be neutralized with bases. | 0 | Organic Reactions |
Complementing alkylation reactions are the reverse, dealkylations. Prevalent are demethylations, which are prevalent in biology, organic synthesis, and other areas, especially for methyl ethers and methyl amines. | 0 | Organic Reactions |
The Barton decarboxylation is a radical reaction in which a carboxylic acid is converted to a thiohydroxamate ester (commonly referred to as a Barton ester). The product is then heated in the presence of a radical initiator and a suitable hydrogen donor to afford the decarboxylated product. This is an example of a reductive decarboxylation. Using this reaction it is possible to remove carboxylic acid moieties from alkyl groups and replace them with other functional groups. (See Scheme 1) This reaction is named after its developer, the British chemist and Nobel laureate Sir Derek Barton (1918–1998). | 0 | Organic Reactions |
Sodium hydroxide is industrially produced as a 50% solution by variations of the electrolytic chloralkali process. Chlorine gas is also produced in this process. Solid sodium hydroxide is obtained from this solution by the evaporation of water. Solid sodium hydroxide is most commonly sold as flakes, prills, and cast blocks.
In 2004, world production was estimated at 60 million dry tonnes of sodium hydroxide, and demand was estimated at 51 million tonnes. In 1998, total world production was around 45 million tonnes. North America and Asia each contributed around 14 million tonnes, while Europe produced around 10 million tonnes. In the United States, the major producer of sodium hydroxide is Olin, which has annual production around 5.7 million tonnes from sites at Freeport, Texas; Plaquemine, Louisiana; St. Gabriel, Louisiana; McIntosh, Alabama; Charleston, Tennessee; Niagara Falls, New York; and Bécancour, Canada. Other major US producers include Oxychem, Westlake, Shintek, and Formosa. All of these companies use the chloralkali process.
Historically, sodium hydroxide was produced by treating sodium carbonate with calcium hydroxide in a metathesis reaction which takes advantage of the fact that sodium hydroxide is soluble, while calcium carbonate is not. This process was called causticizing.
This process was superseded by the Solvay process in the late 19th century, which was in turn supplanted by the Leblanc process and then chloralkali process which is in use today.
Sodium hydroxide is also produced by combining pure sodium metal with water. The byproducts are hydrogen gas and heat, often resulting in a flame.
This reaction is commonly used for demonstrating the reactivity of alkali metals in academic environments; however, it is not commercially viable, as the isolation of sodium metal is typically performed by reduction or electrolysis of sodium compounds including sodium hydroxide. | 1 | Inorganic Reactions + Inorganic Compounds |
This is the fourth member of the polyoxidanes. The first three are water [(mon)oxidane], hydrogen peroxide (dioxidane), and trioxidane. Tetroxidane is more unstable than the previous compounds. The term "tetraoxidane" extends beyond the parent compound to several daughter compounds of the general formula , where R can be hydrogen, halogen atoms, or various inorganic and organic monovalent radicals. The two Rs together can be replaced by a divalent radical, so heterocyclic tetroxidanes also exist. | 1 | Inorganic Reactions + Inorganic Compounds |
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly corrosive base and alkali that decomposes lipids and proteins at ambient temperatures and may cause severe chemical burns. It is highly soluble in water, and readily absorbs moisture and carbon dioxide from the air. It forms a series of hydrates . The monohydrate crystallizes from water solutions between 12.3 and 61.8 °C. The commercially available "sodium hydroxide" is often this monohydrate, and published data may refer to it instead of the anhydrous compound.
As one of the simplest hydroxides, sodium hydroxide is frequently used alongside neutral water and acidic hydrochloric acid to demonstrate the pH scale to chemistry students.
Sodium hydroxide is used in many industries: in the making of wood pulp and paper, textiles, drinking water, soaps and detergents, and as a drain cleaner. Worldwide production in 2004 was approximately 60 million tons, while demand was 51 million tons. | 1 | Inorganic Reactions + Inorganic Compounds |
The Heck reaction is the palladium-catalyzed coupling of an aryl or alkenyl halide with an alkene to form a substituted alkene. Intramolecular variants of the reaction may be used to generate cyclic products containing endo or exo double bonds. Ring sizes produced by the intramolecular Heck reaction range from four to twenty-seven atoms. Additionally, in the presence of a chiral palladium catalyst, the intramolecular Heck reaction may be used to establish tertiary or quaternary stereocenters with high enantioselectivity. A number of tandem reactions, in which the intermediate alkylpalladium complex is intercepted either intra- or intermolecularly before β-hydride elimination, have also been developed. | 0 | Organic Reactions |
Oxocarbenium ions have been utilized in total synthesis on several occasions. A major subunit of (+)-clavosolide was synthesized with a reduction of a six-membered oxocarbenium ring. All the large substituents were found in an equatorial position, and the transformation went through the chair transition state, as predicted.
A second example is seen in the key step of the synthesis of (−)-neopeltolide, which uses another six-membered oxocarbenium ring reduction for a diastereoselective hydride addition. | 0 | Organic Reactions |
The persistent radical effect (PRE) in chemistry describes and explains the selective product formation found in certain free-radical cross-reactions. In these type of reactions, different radicals compete in secondary reactions. The so-called persistent (long-lived) radicals do not self-terminate and only react in cross-couplings. In this way, the cross-coupling products in the product distribution are more prominent.
The effect was first described in 1936 by Bachmann & Wiselogle. They heated pentaphenylethane and observed that the main reaction product was the starting product (87%) with only 2% of tetraphenylethane formed. They concluded that the dissociation of pentaphenylethane into triphenylmethyl and diphenylmethyl radicals was reversible and that persistent triphenylmethyl did not self terminate and transient diphenylmethyl did to a certain extent. In 1964, Perkins performed a similar reaction with phenylazotriphenylmethane in benzene. Again, the dimerization product of the persistent radical (phenylcyclohexydienyl) was absent as reaction product. In 1981, Geiger and Huber found that the photolysis of dimethylnitrosamine into dimethylaminyl radical and nitrous oxide was also completely reversible. A similar effect was observed by Kräutler in 1984 for methylcobalamin. The term persistent radical effect was coined in 1992 by Daikh and Finke in their work related to the thermolysis of a cyanocobalamin model compound.
The PRE is a kinetic feature which provides a self-regulating effect in certain controlled/living radical polymerization systems such as atom transfer radical polymerization and nitroxide mediated polymerization. Propagating radicals P* are rapidly trapped in the deactivation process (with a rate constant of deactivation, k) by species X, which is typically a stable radical such as a nitroxide. The dormant species are activated (with a rate constant k) either spontaneously/thermally, in the presence of light, or with an appropriate catalyst (as in ATRP) to reform the growing centers. Radicals can propagate (k) but also terminate (k). However, persistent radicals (X), as stated above, cannot terminate with each other but only (reversibly) cross-couple with the growing species (k). Thus, every act of radical–radical termination is accompanied by the irreversible accumulation of X. Consequently, the concentration of radicals as well as the probability of termination decreases with time. The growing radicals (established through the activation–deactivation process) then predominantly react with X rather than with themselves. | 0 | Organic Reactions |
is shock-sensitive. Purer samples are more shock-sensitive than those contaminated with elemental sulfur. | 1 | Inorganic Reactions + Inorganic Compounds |
The C-B bonds generated by hydroboration are reactive with various reagents, the most common one being hydrogen peroxide. Because the addition of H-B to olefins is stereospecific, this oxidation reaction will be diastereoselective when the alkene is trisubstituted. Hydroboration-oxidation is thus an excellent way of producing alcohols in a stereospecific and anti-Markovnikov fashion.
Hydroboration can also lead to amines by treating the intermediate organoboranes with monochloramine or O-hydroxylaminesulfonic acid (HSA).
Terminal olefins are converted to the corresponding alkyl bromides and alkyl iodides by treating the organoborane intermediates with bromine or iodine. Such reactions have not however proven very popular, because succinimide based reagents such as NIS and NBS are more versatile and do not require rigorous conditions as do organoboranes.
etc. | 0 | Organic Reactions |
As powerful nucleophiles, enolates react readily with a variety of electrophiles. These reactions generate new C-C bonds and often new stereocenters. The stereoselectivity and regioselectivity is influenced by additives, solvent, counterions, etc. One important class of electrophiles are alkyl halides, and in this case a classic problem arises: O-alkylation vs C-alkylation. Controlling this selectivity has drawn much attention. The negative charge in enolates is concentrated on the oxygen, but that center is also highly solvated, which leads to C-alkylation.
Other important electrophiles are aldehydes/ketones and Michael acceptors. | 0 | Organic Reactions |
Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting alkylation. Alkyl groups can also be removed in a process known as dealkylation. Alkylating agents are often classified according to their nucleophilic or electrophilic character. In oil refining contexts, alkylation refers to a particular alkylation of isobutane with olefins. For upgrading of petroleum, alkylation produces a premium blending stock for gasoline. In medicine, alkylation of DNA is used in chemotherapy to damage the DNA of cancer cells. Alkylation is accomplished with the class of drugs called alkylating antineoplastic agents. | 0 | Organic Reactions |
The A coupling (also known as A coupling reaction or the aldehyde-alkyne-amine reaction), coined by Prof. Chao-Jun Li of McGill University, is a type of multicomponent reaction involving an aldehyde, an alkyne and an amine which react to give a propargylamine.
The reaction proceeds via direct dehydrative condensation and requires a metal catalyst, typically based on ruthenium/copper, gold or silver. Chiral catalyst can be used to give an enantioselective reaction, yielding a chiral amine. The solvent can be water. In the catalytic cycle the metal activates the alkyne to a metal acetylide, the amine and aldehyde combine to form an imine which then reacts with the acetylide in a nucleophilic addition. The reaction type was independently reported by three research groups in 2001 -2002; one report on a similar reaction dates back to 1953.
If the amine substituents have an alpha hydrogen present and provided a suitable zinc or copper catalyst is used, the A coupling product may undergo a further internal hydride transfer and fragmentation to give an allene in a Crabbé reaction. | 0 | Organic Reactions |
The molecule has a cyclic, unsaturated backbone consisting of alternating phosphorus and nitrogen centers, and can be viewed as a trimer of the hypothetical compound . Its classification as a phosphazene highlights its relationship to benzene. Hexafluorophosphazene has a hexagonal ring with six equivalent P–N bonds. Each phosphorus atom is additionally bonded to two fluorine atoms.
The molecule possesses D symmetry, and each phosphorus center is tetrahedral.
The ring in hexachlorophosphazene deviates from planarity and is slightly ruffled (see chair conformation). By contrast, the ring in hexafluorophosphazene is completely planar. | 1 | Inorganic Reactions + Inorganic Compounds |
Enolate activation is the simplest Conia-ene activation mode. In this mode, the carbonyl starting material is treated with a strong base, such as nBuLi, NaH, or tBuOK, to form a metal-stabilized enolate, which then attacks the tethered alkyne and transfers the metal cation. An early example of enolate activation was reported by Taguchi and coworkers in 1999. The authors found that in the presence of catalytic base, alkynyl-substituted malonate esters undergo facile cyclization to the corresponding cyclopentanes. High yields were also obtained with substituted cyanoacetate, sulfonylacetate, and phosphonoacetate analogs. | 0 | Organic Reactions |
Aqueous zinc chloride reacts with zinc oxide to form an amorphous cement that was first investigated in 1855 by Stanislas Sorel. Sorel later went on to investigate the related magnesium oxychloride cement, which bears his name. | 1 | Inorganic Reactions + Inorganic Compounds |
Glycosylation is the process by which a carbohydrate is covalently attached to a target macromolecule, typically proteins and lipids. This modification serves various functions. For instance, some proteins do not fold correctly unless they are glycosylated. In other cases, proteins are not stable unless they contain oligosaccharides linked at the amide nitrogen of certain asparagine residues. The influence of glycosylation on the folding and stability of glycoprotein is twofold. Firstly, the highly soluble glycans may have a direct physicochemical stabilisation effect. Secondly, N-linked glycans mediate a critical quality control check point in glycoprotein folding in the endoplasmic reticulum. Glycosylation also plays a role in cell-to-cell adhesion (a mechanism employed by cells of the immune system) via sugar-binding proteins called lectins, which recognize specific carbohydrate moieties. Glycosylation is an important parameter in the optimization of many glycoprotein-based drugs such as monoclonal antibodies. Glycosylation also underpins the ABO blood group system. It is the presence or absence of glycosyltransferases which dictates which blood group antigens are presented and hence what antibody specificities are exhibited. This immunological role may well have driven the diversification of glycan heterogeneity and creates a barrier to zoonotic transmission of viruses. In addition, glycosylation is often used by viruses to shield the underlying viral protein from immune recognition. A significant example is the dense glycan shield of the envelope spike of the human immunodeficiency virus.
Overall, glycosylation needs to be understood by the likely evolutionary selection pressures that have shaped it. In one model, diversification can be considered purely as a result of endogenous functionality (such as cell trafficking). However, it is more likely that diversification is driven by evasion of pathogen infection mechanism (e.g. Helicobacter attachment to terminal saccharide residues) and that diversity within the multicellular organism is then exploited endogenously.
Glycosylation can also module the thermodynamic and kinetic stability of the proteins. | 0 | Organic Reactions |
Of some interest in organic synthesis, electropositive metals react with many organic halides in a metal-halogen exchange:
The resulting organometallic compound is susceptible to hydrolysis:
Heavily studied examples are found in organolithium chemistry and organomagnesium chemistry. Some illustrative cases follow.
Lithium-halogen exchange is essentially irrelevant to remediation, but the method is useful for fine chemical synthesis. Sodium metal has been used for dehalogenation process.
Removal of halogen atom from arene-halides in the presence of Grignard agent and water for the formation of new compound is known as Grignard degradation. Dehalogenation using Grignard reagents is a two steps hydrodehalogenation process. The reaction begins with the formation of alkyl/arene-magnesium-halogen compound, followed by addition of proton source to form dehalogenated product. Egorov and his co-workers have reported dehalogenation of benzyl halides using atomic magnesium in 3P state at 600 °C. Toluene and bi-benzyls were produced as the product of the reaction. Morrison and his co-workers also reported dehalogenation of organic halides by flash vacuum pyrolysis using magnesium. | 0 | Organic Reactions |
The Marschalk reaction in chemistry is the sodium dithionite promoted reaction of a phenolic anthraquinone with an aldehyde to yield a substituted phenolic anthraquinone after the addition of acid.
The mechanism can be found in the book Named Reactions in Organic Chemistry, and its more intuitive version is provided below:
One of the first applications of this reaction was reported in 1985. | 0 | Organic Reactions |
Edman degradation, developed by Pehr Edman, is a method of sequencing amino acids in a peptide. In this method, the amino-terminal residue is labeled and cleaved from the peptide without disrupting the peptide bonds between other amino acid residues. | 0 | Organic Reactions |
Methionine synthase regenerates methionine (Met) from homocysteine (Hcy). The overall reaction transforms 5-methyltetrahydrofolate (N-MeTHF) into tetrahydrofolate (THF) while transferring a methyl group to Hcy to form Met. Methionine Syntheses can be cobalamin-dependent and cobalamin-independent: Plants have both, animals depend on the methylcobalamin-dependent form.
In methylcobalamin-dependent forms of the enzyme, the reaction proceeds by two steps in a ping-pong reaction. The enzyme is initially primed into a reactive state by the transfer of a methyl group from N-MeTHF to Co(I) in enzyme-bound cobalamin (Cob), forming methyl-cobalamin(Me-Cob) that now contains Me-Co(III) and activating the enzyme. Then, a Hcy that has coordinated to an enzyme-bound zinc to form a reactive thiolate reacts with the Me-Cob. The activated methyl group is transferred from Me-Cob to the Hcy thiolate, which regenerates Co(I) in Cob, and Met is released from the enzyme. | 0 | Organic Reactions |
A solution of 13.0 g (0.1 mol) of 1-octanol in 25 mL of dichloromethane was added dropwise to a solution of 16.1 g (0.1 mol) of diethylaminosulfur trifluoride in 60 mL of dichloromethane cooled to –70° to –65°. The reaction mixture was warmed to 25°, 50 mL of water was added, and the lower organic layer was separated and dried with anhydrous magnesium sulfate and distilled to give 12.0 g (90%) of 1-fluorooctane as a colorless liquid, bp 42–43° (20 mm). F NMR (CClF): -218.8 ppm (tt, J = 49 Hz, J = 25 Hz). | 0 | Organic Reactions |
Special methods are used to produce films of CdS as components in some photoresistors and solar cells. In the chemical bath deposition method, thin films of CdS have been prepared using thiourea as the source of sulfide anions and an ammonium buffer solution to control pH:
:Cd + HO + (NH)CS + 2 NH → CdS + (NH)CO + 2 NH
Cadmium sulfide can be produced using metalorganic vapour phase epitaxy and MOCVD techniques by the reaction of dimethylcadmium with diethyl sulfide:
:Cd(CH) + EtS → CdS + CHCH + CH
Other methods to produce films of CdS include
* Sol–gel techniques
* Sputtering
* Electrochemical deposition
* Spraying with precursor cadmium salt, sulfur compound and dopant
* Screen printing using a slurry containing dispersed CdS | 1 | Inorganic Reactions + Inorganic Compounds |
The first examples of nontrigonal pnictogen compound were synthesized by Arduengo and co-workers in 1984, through condensation of a diketoamine with a phosphorus trihalide in the presence of base. This group reported also on the first systematic investigations into its chemical behavior. Later, on similar routes, the corresponding and isostructural arsenic and antimony species were also synthesized. Other synthetic methods involve deprotonation of OH or NH groups in the presence of ECl (E=P, As, Sb and Bi), salt metathesis or reduction of pentavalent pnictogen compounds. | 1 | Inorganic Reactions + Inorganic Compounds |
As early as the 1920s, the concept of using hot water and alkali catalysts to produce oil out of biomass was proposed. In 1939, U.S. patent 2,177,557, described a two-stage process in which a mixture of water, wood chips, and calcium hydroxide is heated in the first stage at temperatures in a range of , with the pressure "higher than that of saturated steam at the temperature used." This produces "oils and alcohols" which are collected. The materials are then subjected in a second stage to what is called "dry distillation", which produces "oils and ketones". Temperatures and pressures for this second stage are not disclosed.
These processes were the foundation of later HTL technologies that attracted research interest especially during the 1970s oil embargo. It was around that time that a high-pressure (hydrothermal) liquefaction process was developed at the Pittsburgh Energy Research Center (PERC) and later demonstrated (at the 100 kg/h scale) at the Albany Biomass Liquefaction Experimental Facility at Albany, Oregon, US. In 1982, Shell Oil developed the HTU™ process in the Netherlands. Other organizations that have previously demonstrated HTL of biomass include Hochschule für Angewandte Wissenschaften Hamburg, Germany, SCF Technologies in Copenhagen, Denmark, EPA’s Water Engineering Research Laboratory, Cincinnati, Ohio, USA, and Changing World Technology Inc. (CWT), Philadelphia, Pennsylvania, USA. Today, technology companies such as [http://www.licella.com.au Licella/Ignite Energy Resources] (Australia), [https://arbiosbiotech.com Arbios Biotech], a Licella/Canfor joint venture, [http://altacaenergy.com Altaca Energy] (Turkey), [https://circlianordic.com/ Circlia Nordic] (Denmark), [http://steeperenergy.com/ Steeper Energy] (Denmark, Canada) continue to explore the commercialization of HTL. Construction has begun in Teesside, UK, for a catalytic hydrothermal liquefaction plant that aims to process 80,000 tonnes per year of mixed plastic waste by 2022. | 0 | Organic Reactions |
The two reactions in the HyS cycle are as follows:
# HSO → HO + SO + ½ O (thermochemical, T > 800 °C)
# SO + 2 HO → HSO + H (electrochemical, T = 80-120 °C)
: Net reaction: HO → H + ½ O
Sulfur dioxide acts to depolarize the anode of the electrolyzer. This results in a significant decrease in the reversible cell potential (and, therefore, the electric power requirement) for reaction (2). The standard cell potential for reaction (2) is -0.158 V at 298.15 K, compared to -1.229 V for the electrolysis of water (with oxygen evolution as the anodic reaction). | 1 | Inorganic Reactions + Inorganic Compounds |
Optimal conditions for enantio-selective nucleophilic epoxidation depend on the substrate employed. Although a variety of substrates may be epoxidized using nucleophilic methods, each particular method tends to have limited substrate scope. This section describes asymmetric nucleophilic epoxidation methods, organizing them according to the constitution and configuration of the unsaturated substrate. | 0 | Organic Reactions |
The Lumière–Barbier method is a method of acetylating aromatic amines in aqueous solutions. Illustrative is the acetylation of aniline. First aniline is dissolved in water using one equivalent of hydrochloric acid. This solution is subsequently treated, sequentially, with acetic anhydride and aqueous sodium acetate. Aniline attacks acetic anhydride followed by deprotonation of the ammonium ion:
Acetate then acts as a leaving group:
The acetanilide product is insoluble in water and can therefore be filtered off as crystals. | 0 | Organic Reactions |
Magnesium oxalate is an organic compound comprising a magnesium cation with a 2+ charge bonded to an oxalate anion. It has the chemical formula MgCO. Magnesium oxalate is a white solid that comes in two forms: an anhydrous form and a dihydrate form where two water molecules are complexed with the structure. Both forms are practically insoluble in water and are insoluble in organic solutions. | 1 | Inorganic Reactions + Inorganic Compounds |
The product scope of this reaction is extremely broad with the use of different substrates; however development of different functionalities has required accompanied studies to determine the proper catalyst system. The most typical class of reactions involves coupling between C–COOH and C–X bonds, however C–COOH and C–M cross-coupling, homo-coupling of carboxylic acids, heck coupling, and dehydrogenative cross-coupling can also be including in this class as they release CO. Heteroatom cross coupling reactions involving formation of C–N, C–S, C–P, and C–X bonds have also been demonstrated. | 0 | Organic Reactions |
Following 2D SDS PAGE the proteins can be transferred to a polyvinylidene difluoride (PVDF) blotting membrane for further analysis. Edman degradations can be performed directly from a PVDF membrane. N-terminal residue sequencing resulting in five to ten amino acid may be sufficient to identify a Protein of Interest (POI). | 0 | Organic Reactions |
Like many oxometalates, orthovanadate is subject to a number of reactions, which have been analyzed by V NMR studies. At high pH, ions exist in equilibrium with . At lower pH's, condensation ensues to give various polyoxovanadates. Ultimately, decavanadate is formed. | 1 | Inorganic Reactions + Inorganic Compounds |
Aluminium hydroxide is a feedstock for the manufacture of other aluminium compounds: calcined aluminas, aluminium sulfate, polyaluminium chloride, aluminium chloride, zeolites, sodium aluminate, activated alumina, and aluminium nitrate.
Freshly precipitated aluminium hydroxide forms gels, which are the basis for the application of aluminium salts as flocculants in water purification. This gel crystallizes with time. Aluminium hydroxide gels can be dehydrated (e.g. using water-miscible non-aqueous solvents like ethanol) to form an amorphous aluminium hydroxide powder, which is readily soluble in acids. Heating converts it to activated aluminas, which are used as desiccants, adsorbent in gas purification, and catalyst supports. | 1 | Inorganic Reactions + Inorganic Compounds |
Straight-chain azanes are sometimes indicated by the prefix n- (for normal) where a non-linear isomer exists. Although this is not strictly necessary, the usage is common in cases where there is an important difference in properties between the straight-chain and branched-chain isomers.
The members of the series (in terms of number of nitrogen atoms) are named as follows:
:azane (or ammonia), NH - one nitrogen and three hydrogen
:diazane (or hydrazine), - two nitrogen and four hydrogen
:triazane, - three nitrogen and five hydrogen
Azanes with three or more nitrogen atoms are named by adding the suffix -azane to the appropriate numerical multiplier prefix. Hence, triazane, ; tetrazane or tetraazane, ; pentazane or pentaazane, ; hexazane or hexaazane, ; etc. The prefix is generally Greek, with the exceptions of nonaazane which has a Latin prefix, and undecaazane and tridecaazane which have mixed-language prefixes. | 1 | Inorganic Reactions + Inorganic Compounds |
Related to the azanes are a homologous series of functional groups, side-chains, or radicals with the general chemical formula . Examples include azanyl () and hydrazinyl. This group is generally abbreviated with the symbol N. | 1 | Inorganic Reactions + Inorganic Compounds |
In the following example, elemental aluminium reduces the oxide of another metal, in this common example iron oxide, because aluminium forms stronger and more stable bonds with oxygen than iron:
: FeO + 2 Al → 2 Fe + AlO
The products are aluminium oxide, elemental iron, and a large amount of heat. The reactants are commonly powdered and mixed with a binder to keep the material solid and prevent separation.
Other metal oxides can be used, such as chromium oxide, to generate the given metal in its elemental form. For example, a copper thermite reaction using copper oxide and elemental aluminium can be used for creating electric joints in a process called cadwelding, that produces elemental copper (it may react violently):
: 3 CuO + 2 Al → 3 Cu + AlO
Thermites with nanosized particles are described by a variety of terms, such as metastable intermolecular composites, super-thermite, nano-thermite, and nanocomposite energetic materials. | 1 | Inorganic Reactions + Inorganic Compounds |
Similar to intermolecular reactions, intramolecular reactions can show significant stereoselectivity from the ground state conformation of the molecule. In the intramolecular Diels-Alder reaction depicted below, the lowest energy conformation yields the observed product. The structure minimizing repulsive steric interactions provides the observed product by having the lowest barrier to a transition state for the reaction. Though no external attack by a reagent occurs, this reaction can be thought of similarly to those modeled with peripheral attack; the lowest energy conformation is the most likely to react for a given reaction.
The lowest energy conformations of macrocycles also influence intramolecular reactions involving transannular bond formation. In the intramolecular Michael addition sequence below, the ground state conformation minimizes transannular interactions by placing the sp centers at the appropriate vertices, while also minimizing diaxial interactions. | 0 | Organic Reactions |
The Elbs reaction is an organic reaction describing the pyrolysis of an ortho methyl substituted benzophenone to a condensed polyaromatic. The reaction is named after its inventor, the German chemist Karl Elbs, also responsible for the Elbs oxidation. The reaction was published in 1884. Elbs however did not correctly interpret the reaction product due to a lack of knowledge about naphthalene structure. | 0 | Organic Reactions |
Boric acid also dissolves in anhydrous sulfuric acid according to the equation:
The product is an extremely strong acid, even stronger than the original oleum. | 1 | Inorganic Reactions + Inorganic Compounds |
The enantioselective version of the Tsuji–Trost reaction is called the Trost asymmetric allylic alkylation (Trost AAA) or simply, asymmetric allylic alkylation (AAA). These reactions are often used in asymmetric synthesis. The reaction was originally developed with a palladium catalyst supported by the Trost ligand, although suitable conditions have greatly expanded since then.
Enantioselectivity can be imparted to the reaction during any of the steps aside from the decomplexation of the palladium from the alkene since the stereocenter is already set at that point. Five main ways have been conceptualized to take advantage of these steps and yield enantioselective reaction conditions.
These methods of enantiodiscrimination were previously reviewed by Trost:
# Preferential ionization via enantioselective olefin complexation
# Enantiotopic ionization of leaving groups
# Attack at enantiotopic ends of the allyl complex
# Enantioface exchange in the -allyl complex
# Differentiation of prochiral nucleophile faces
The favored method for enantiodiscrimination is largely dependent on the substrate of interest, and in some cases, the enantioselectivity may be influenced by several of these factors. | 0 | Organic Reactions |
Enantioselective intermolecular cyclopropanation has been applied to the synthesis of the chiral cyclopropane antibiotics cilastatin.
Tandem cyclopropanation/fragmentation is a key step in the synthesis of 12-hydroxyeicosatetraenoic acid. | 0 | Organic Reactions |
Regioselective and stereoselective formation of carbon-carbon bonds adjacent to carbonyl group is an important procedure in organic chemistry. Alkylation reaction of enolates has been the main focus of the field. Both A. G. Myers and D. A. Evans developed asymmetric alkylation reactions for enolates.
The apparent shortcoming for enolate alkylation reactions is over-alkylation, even if the amount of base added for enolization as well as the reaction temperature are carefully controlled. The ketene formation during the deprotonation process for substrates possessing Evans' oxazolidinone is also a main side reaction for the related alkylation reactions. Development in the field of enamine chemistry and the utilization of imine derivatives of enolates managed to provide an alternative for enolate alkylation reactions.
In 1963, G. Stork reported the first enamine alkylation reaction for ketones - Stork enamine alkylation reaction.
In 1976, Meyers reported the first alkylation reaction of metallated azaenolates of hydrazones with an acyclic amino acid-based auxiliary. Compared with the free carbonyl compounds and the chiral enamine species reported previously, the hydrazones exhibit higher reactivity, regioselectivity and stereoselectivity.
The combination of cyclic amino acid derivatives (SAMP and RAMP) and the powerful hydrazone techniques were pioneered by E. J. Corey and D. Enders in 1976, and were independently developed by D. Enders later. Both SAMP and RAMP are synthesized from amino acids. The detailed synthesis of these two auxiliaries are shown below. | 0 | Organic Reactions |
Aluminium hydroxide is amphoteric. In acid, it acts as a Brønsted–Lowry base. It neutralizes the acid, yielding a salt:
In bases, it acts as a Lewis acid by binding hydroxide ions: | 1 | Inorganic Reactions + Inorganic Compounds |
In 1850, Charles-Adolphe Wurtz described a colorless platinum tetrammine with the formula [Pt(etn)]Cl 2HO; Wolffram (H. Wolffram, Dissertation, Königsberg, 1900.), whom the compound is named after, obtained a red salt from this by action of hydrogen peroxide in hydrochloric acid, and initially considered it to be isomeric with Wurtz’s salt. With no known case of plato-tetrammine isomerism at the time, this prompted extensive discussion in the literature of the true nature and properties of Wolffram’s Red Salt. | 1 | Inorganic Reactions + Inorganic Compounds |
Mycophenolic acid is a Penicillium metabolite that was originally prepared via a key benzannulation step. An alkyne and a cyclobutenone were reacted to form a substituted phenol in a single step in a 73% yield (Scheme 14). Mycophenolic acid was prepared in nine steps in an overall yield of 17-19%.
In the synthesis of highly substituted indoles performed by Danheiser, the key step was a benzannulation reaction using cyclobutenone and ynamides to produce highly substituted aniline derivatives. In this case, the ortho position can be functionalized with various substituents. Following the benzannulation reaction with various heterocyclization reactions can provide access to substituted indoles (Scheme 15).
Danheiser also used the benzannulation with ynamides for the synthesis of polycyclic benzofused nitrogen heterocycles followed by ring-closing metathesis (Scheme 16) for the total synthesis of (+)-FR900482, an anticancer agent.
Kowalski used the benzannulation reaction with siloxyacetylenes for the first time, reacting them with cyclobutenones to synthesize a substituted phenol for the total synthesis of Δ-6-tetrahydrocannabinol (Scheme 17).
The benzannulation reaction was used by Smith in the total synthesis of cylindrocyclophanes specifically (−)-Cylindrocyclophane F. He utilized the reaction of a siloxyalkyne and a cyclobutenone to construct the dihydroxyl aromatic intermediate for an olefin metathesis reaction to access the target (Scheme 18).
An outstanding application of Danheiser benzannulation in 6-step synthesis of dictyodendrins was demonstrated by Zhang and Ready. They obtained the cyclobutenone substrate using a hetero-[2+2] cycloaddition between aryl ynol ethers (aryl ketene precursors), and the following benzannulation enabled the rapid construction of the carbazole cole of dictyodendrins F, H and I. The successful usage of Danheiser benzannulation allows Zhang and Ready to achieve the so-far shortest synthesis of dictyodendrin natural products. | 0 | Organic Reactions |
Typically, the rearrangement is carried out just after the formation of the divinylcyclopropane, in the same pot. Heating is sometimes necessary, particularly for trans substrates, which must undergo epimerization prior to rearrangement. With enough energy to surmount activation barriers, however, the isomerization is usually very efficient. | 0 | Organic Reactions |
The Deacon process, invented by Henry Deacon, is a process used during the manufacture of alkalis (the initial end product was sodium carbonate) by the Leblanc process. Hydrogen chloride gas was converted to chlorine gas, which was then used to manufacture a commercially valuable bleaching powder, and at the same time the emission of waste hydrochloric acid was curtailed. To some extent this technically sophisticated process superseded the earlier manganese dioxide process. | 1 | Inorganic Reactions + Inorganic Compounds |
Polyphosphazenes obtained from polymerised hexachlorophosphazene (polydichlorophosphazene) have gathered attention within the field of inorganic polymers and probed investigations on the properties of elastomeric and thermoplastic derivatives. Some of them appear promising for future applications as fibre- or membrane-forming high performance materials, since they combine transparency, backbone flexibility, tunable hydrophilicity or hydrophobicity, and various other desirable properties.
Current commercial applications for polyphosphazene rubber components are in O-rings, fuel lines and shock absorbers, where the polyphosphazenes confer fire resistance, imperviousness to oils and flexibility even at very low temperatures. | 1 | Inorganic Reactions + Inorganic Compounds |
These easily available and sterically constrained compounds are potentially suitable for an application in a wide variety of secondary processes such as small molecule activation or the generation of new catalysts based on main-group and transition-metal elements. | 1 | Inorganic Reactions + Inorganic Compounds |
NCAs are typically prepared by phosgenation of amino acids:
They were first synthesized by Hermann Leuchs by heating an N-ethoxycarbonyl or N-methoxycarbonyl amino acid chloride in a vacuum at 50-70 °C:
A moisture-tolerant route to unprotected NCAs employs epoxides as scavengers of hydrogen chloride.
This synthesis of NCAs is sometimes called the . The relatively high temperatures necessary for this cyclization results in the decomposition of several NCAs. Of several improvements, one notable procedure involves treating an unprotected amino acid with phosgene or its trimer. | 0 | Organic Reactions |
Some representative examples of Crich’s β-mannosylation are shown in Scheme 3. It is noteworthy that, with this method in hand, primary, secondary, and tertiary alcohols (9, 12, and 13) all serve as glycosyl acceptors effectively in terms of yields and selectivity. In a recent version, the β-mannosylation of thioglycoside 14 and its analogues were examined to prepare sterically hindered glycosides, in which PhSOTf (or other newly developed sulfur-type oxidants) served as a convenient reagent for the in situ generation of the glycosyl triflate from 14, thus facilitating the reaction. | 0 | Organic Reactions |
GaN crystals can be grown from a molten Na/Ga melt held under 100 atmospheres of pressure of N at 750 °C. As Ga will not react with N below 1000 °C, the powder must be made from something more reactive, usually in one of the following ways:
: 2 Ga + 2 NH → 2 GaN + 3 H
: GaO + 2 NH → 2 GaN + 3 HO
Gallium nitride can also be synthesized by injecting ammonia gas into molten gallium at at normal atmospheric pressure. | 1 | Inorganic Reactions + Inorganic Compounds |