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In 2016 the first GaN CMOS logic using PMOS and NMOS transistors was reported with gate lengths of 0.5 μm (gate widths of the PMOS and NMOS transistors were 500 μm and 50 μm, respectively). | 1 | Inorganic Reactions + Inorganic Compounds |
Thermate composition is a thermite enriched with a salt-based oxidizer (usually nitrates, e.g., barium nitrate, or peroxides). In contrast with thermites, thermates burn with evolution of flame and gases. The presence of the oxidizer makes the mixture easier to ignite and improves penetration of target by the burning composition, as the evolved gas is projecting the molten slag and providing mechanical agitation. This mechanism makes thermate more suitable than thermite for incendiary purposes and for emergency destruction of sensitive equipment (e.g., cryptographic devices), as thermite's effect is more localized. | 1 | Inorganic Reactions + Inorganic Compounds |
Some alcohols are reduced to alkanes when treated with hydrosilanes in the presence of a strong Lewis acid. Brønsted acids may also be used. Tertiary alcohols undergo facile reduction using boron trifluoride etherate as the Lewis acid. Primary alcohols require an excess of the silane, a stronger Lewis acid, and long reaction times.
Skeletal rearrangements are sometimes induced. Another side reaction is nucleophilic attack of the conjugate base on the intermediate carbocation. In organosilane reductions of substrates bearing prostereogenic groups, diastereoselectivity is often high. Reduction of either diastereomer of 2-phenyl-2-norbornanol leads exclusively to the endo diastereomer of 2-phenylnorbornane. None of the exo diastereomer was observed.
Allylic alcohols may be deoxygenated in the presence of tertiary alcohols when ethereal lithium perchlorate is employed as a source of Li.
Reductions of alkyl halides and triflates gives poorer yields in general than reductions of alcohols. A Lewis or Bronsted acid is required. | 0 | Organic Reactions |
The term methylation in organic chemistry refers to the alkylation process used to describe the delivery of a group. | 0 | Organic Reactions |
Cubic zirconium tungstate (alpha-ZrWO), one of the several known phases of zirconium tungstate (ZrWO) is perhaps one of the most studied materials to exhibit negative thermal expansion. It has been shown to contract continuously over a previously unprecedented temperature range of 0.3 to 1050 K (at higher temperatures the material decomposes). Since the structure is cubic, as described below, the thermal contraction is isotropic - equal in all directions. There is much ongoing research attempting to elucidate why the material exhibits such dramatic negative thermal expansion.
This phase is thermodynamically unstable at room temperature with respect to the binary oxides ZrO and WO, but may be synthesised by heating stoichiometric quantities of these oxides together and then quenching the material by rapidly cooling it from approximately 900 °C to room temperature.
The structure of cubic zirconium tungstate consists of corner-sharing ZrO octahedral and WO tetrahedral structural units. Its unusual expansion properties are thought to be due to vibrational modes known as Rigid Unit Modes (RUMs), which involve the coupled rotation of the polyhedral units that make up the structure, and lead to contraction. | 1 | Inorganic Reactions + Inorganic Compounds |
Transamination is a chemical reaction that transfers an amino group to a ketoacid to form new amino acids.This pathway is responsible for the deamination of most amino acids. This is one of the major degradation pathways which convert essential amino acids to non-essential amino acids (amino acids that can be synthesized de novo by the organism).
Transamination in biochemistry is accomplished by enzymes called transaminases or aminotransferases. α-ketoglutarate acts as the predominant amino-group acceptor and produces glutamate as the new amino acid.
:Aminoacid + α-ketoglutarate ↔ α-keto acid + glutamate
Glutamate's amino group, in turn, is transferred to oxaloacetate in a second transamination reaction yielding aspartate.
:Glutamate + oxaloacetate ↔ α-ketoglutarate + aspartate | 0 | Organic Reactions |
Barium chlorate is used to produce chloric acid, the formal precursor to all chlorate salts, through its reaction with dilute sulfuric acid, which results in a solution of chloric acid and insoluble barium sulfate precipitate:
:Ba(ClO) + HSO → 2 HClO + BaSO
Both the chlorate and the acid should be prepared as dilute solutions before mixing, such that the chloric acid produced is dilute, as concentrated solutions of chloric acid (above 30%) are unstable and prone to decompose, sometimes explosively. | 1 | Inorganic Reactions + Inorganic Compounds |
The mechanism of fluorination by SF is assumed to resemble chlorination by phosphorus pentachloride. Hydrogen fluoride, a useful solvent for these reactions, activates SF:
Species of the type ROSF are often invoked as intermediates. In the case of aldehydes and ketones, SF4 is thought to initially add across the double bond to give R2CFOSF. | 0 | Organic Reactions |
Alpha-substitution reactions occur at the position next to the carbonyl group,
the α-position, and involve the substitution of an α hydrogen atom
by an electrophile, E, through either an enol or enolate ion intermediate. | 0 | Organic Reactions |
Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na) and iodide anions (I) in a crystal lattice. It is used mainly as a nutritional supplement and in organic chemistry. It is produced industrially as the salt formed when acidic iodides react with sodium hydroxide. It is a chaotropic salt. | 1 | Inorganic Reactions + Inorganic Compounds |
Aluminum-substituted tobermorite is understood to be a key ingredient responsible for the longevity of ancient undersea Roman concrete. The volcanic ash that Romans used for construction of sea walls contained phillipsite, and an interaction with sea water actually caused the crystalline structures in the concrete to expand and strengthen, making that material substantially more durable than modern concrete when exposed to sea water. | 1 | Inorganic Reactions + Inorganic Compounds |
The requirement for a good leaving group is relaxed in conjugate base elimination reactions. These reactions include loss of a leaving group in the β position of an enolate as well as the regeneration of a carbonyl group from the tetrahedral intermediate in nucleophilic acyl substitution. Under forcing conditions, even amides can be made to undergo basic hydrolysis, a process that involves the expulsion of an extremely poor leaving group, RN. Even more dramatic, decarboxylation of benzoate anions can occur by heating with copper or CuO, involving the loss of an aryl anion. This reaction is facilitated by the fact that the leaving group is most likely an arylcopper compound rather than the much more basic alkali metal salt.
This dramatic departure from normal leaving group requirements occurs mostly in the realm of C=O double bond formation where formation of the very strong C=O double bond can drive otherwise unfavorable reactions forward. The requirement for a good leaving group is still relaxed in the case of C=C bond formation via E1cB mechanisms, but because of the relative weakness of the C=C double bond, the reaction still exhibits some leaving group sensitivity. Notably, changing the leaving groups identity (and willingness to leave) can change the nature of the mechanism in elimination reactions. With poor leaving groups, the E1cB mechanism is favored, but as the leaving groups ability changes, the reaction shifts from having a rate determining loss of leaving group from carbanionic intermediate B via TS BC through having a rate determining deprotonation step via TS AB (not pictured) to a concerted E2 elimination. In the latter situation, the leaving group X has become good enough that the former transition state connecting intermediates B and C has become lower in energy than B, which is no longer a stationary point on the potential energy surface for the reaction. Because only one transition state connects starting material A and product C, the reaction is now concerted (albeit very asynchronous in the pictured case) due to the increase in leaving group ability of X. | 0 | Organic Reactions |
Lanthanum(III) acetate forms colorless crystals.
Lanthanum acetate dissolves in water.
Lanthanum acetate forms hydrates of the composition , where n = 1 and 1.5.
Lanthanum acetate and its hydrates decompose when heated. | 1 | Inorganic Reactions + Inorganic Compounds |
Intramolecular Diels–Alder (IMDA) reactions pair tethered dienes and dienophiles in a [4+2] fashion, the most common being terminal substitution. These transformations are popular in total synthesis and have seen a wide spread use in advance to numerous difficult synthetic targets. One such use is the application of an enantioselective IMDA transformation in the asymmetric synthesis of the marine toxin (10).
The synthesis of demonstrated the utility of cationic Cu(II)bis(oxazoline) complex catalyzed IMDA reactions to give bicyclic products with as many as four neighboring stereogenic centers (figure 3). A rather recent application of IMDA reactions in complex molecule synthesis is the IMDA approach to the tricyclic core of palhinine lycopodium alkaloids, a class of natural products isolated from nodding club moss.
N–heterocyclic carbenes (NHCs) are an emerging class of organocatalysts that are able to induce Umpolung reactivity as well as normal polarity transformations, however until recently these have not been broadly used in total synthesis due to limited substrate scope. An interesting expansion in the use of these organocatalysts is the NHC catalyzed olefin isomerization/IMDA cascade reaction to give unique bicyclic scaffolds. Dienyl esters such as 11 were transformed into substituted bicyclo[2.2.2]octanes via an isomerization step stabilized by a hemiacetal azolium intermediate (13). The activation barrier of isomerization of 1,3–hexadiene through a [1,5]–shift is 41 Kcal mol–1 and is expected to increase with conjugation to the ester, thus uncatalyzed isomerization is unlikely. This provides the advantage of bypassing a high barrier of activation, providing access to previously unobtainable IMDA derivatives. | 0 | Organic Reactions |
Heteroleptic complexes containing chloride are numerous. Most hydrated metal halides are members of this class. Hexamminecobalt(III) chloride and Cisplatin (cis-Pt(NH)Cl) are prominent examples of metal-ammine-chlorides. | 1 | Inorganic Reactions + Inorganic Compounds |
Transacetylation uses vinyl acetate as an acetyl donor and lipase as a catalyst. This methodology allows the preparation of enantio-enriched alcohols and acetates. | 0 | Organic Reactions |
Diazo compounds may be explosive and should be handled with care. Very often, the diazocarbonyl compound is prepared and immediately used via treatment of the corresponding acid chloride with an excess of diazomethane (see Eq. (18) below for an example). Reactions mediated by copper are typically on the order of hours, and in some cases, slow addition of the diazocarbonyl compound is necessary. Reactions should be carried out under an inert atmosphere in anhydrous conditions. | 0 | Organic Reactions |
Crystalline LaAlO has a relatively high relative dielectric constant of ~25. LAO's crystal structure is a rhombohedral distorted perovskite with a pseudocubic lattice parameter of 3.787 angstroms at room temperature (although one source claims the lattice parameter is 3.82). Polished single crystal LAO surfaces show twin defects visible to the naked eye. | 1 | Inorganic Reactions + Inorganic Compounds |
Convenient generation of a directing group on the nitrogen of indoles is possible through treatment with an organolithium reagent and carbon dioxide. A similar method can be applied for lateral lithiations of ortho-tolyl anilines.
Oxazoles containing two methyl groups exhibit interesting selectivity patterns. In the absence of a directing substituent, the methyl group closer to the more electronegative oxygen atom is selectively metalated. However, in the presence of a directing substituent, the director fully controls the site of lithiation. | 0 | Organic Reactions |
Organic chemistry has a strong tradition of naming a specific reaction to its inventor or inventors and a long list of so-called named reactions exists, conservatively estimated at 1000. A very old named reaction is the Claisen rearrangement (1912) and a recent named reaction is the Bingel reaction (1993). When the named reaction is difficult to pronounce or very long as in the Corey–House–Posner–Whitesides reaction it helps to use the abbreviation as in the CBS reduction. The number of reactions hinting at the actual process taking place is much smaller, for example the ene reaction or aldol reaction.
Another approach to organic reactions is by type of organic reagent, many of them inorganic, required in a specific transformation. The major types are oxidizing agents such as osmium tetroxide, reducing agents such as lithium aluminium hydride, bases such as lithium diisopropylamide and acids such as sulfuric acid.
Finally, reactions are also classified by mechanistic class. Commonly these classes are (1) polar, (2) radical, and (3) pericyclic. Polar reactions are characterized by the movement of electron pairs from a well-defined source (a nucleophilic bond or lone pair) to a well-defined sink (an electrophilic center with a low-lying antibonding orbital). Participating atoms undergo changes in charge, both in the formal sense as well as in terms of the actual electron density. The vast majority of organic reactions fall under this category. Radical reactions are characterized by species with unpaired electrons (radicals) and the movement of single electrons. Radical reactions are further divided into chain and nonchain processes. Finally, pericyclic reactions involve the redistribution of chemical bonds along a cyclic transition state. Although electron pairs are formally involved, they move around in a cycle without a true source or sink. These reactions require the continuous overlap of participating orbitals and are governed by orbital symmetry considerations. Of course, some chemical processes may involve steps from two (or even all three) of these categories, so this classification scheme is not necessarily straightforward or clear in all cases. Beyond these classes, transition-metal mediated reactions are often considered to form a fourth category of reactions, although this category encompasses a broad range of elementary organometallic processes, many of which have little in common and very specific. | 0 | Organic Reactions |
Aluminium hydroxide finds use as a fire retardant filler for polymer applications. It is selected for these applications because it is colorless (like most polymers), inexpensive, and has good fire retardant properties. Magnesium hydroxide and mixtures of huntite and hydromagnesite are used similarly. It decomposes at about , absorbing a considerable amount of heat in the process and giving off water vapour.
In addition to behaving as a fire retardant, it is very effective as a smoke suppressant in a wide range of polymers, most especially in polyesters, acrylics, ethylene vinyl acetate, epoxies, polyvinyl chloride (PVC) and rubber.
Aluminium hydroxide is used as filler in some artificial stone compound material, often in acrylic resin. | 1 | Inorganic Reactions + Inorganic Compounds |
The primary limitations of TMM cycloadditions employing diazenes are competitive MCP and dimer formation. To circumvent these problems, either very high concentrations of alkene must be used or the cycloaddition must be intramolecular. Stereoselectivity and site selectivity may also be higher in intramolecular variants of cycloadditions starting from diazenes.
Usually, unless a cyclic pi system is involved TMM cycloadditions exhibit 2π periselectivity and do not react with larger pi systems. Polar MCPs, for example, react only with the 2,3 double bond of polyunsaturated esters.
Transition-metal catalyzed reactions have the potential to quickly generate an interesting functionality. Propellanes have been generated from intramolecular cyclization under palladium catalysis.
Silylated allylic acetates may be employed for intra- or intermolecular applications. Carbonyl compounds may be used as the 2π component under the appropriate conditions. For instance, in the presence of an indium co-catalyst, the reactive 2π component of the cycloaddition below switches from the C-C to the C-O double bond.
Polarized trimethylenemethanes generated from polar MCPs are also useful substrates for (3+2) reactions with polar double bonds as the 2π component. Orthoester products are generally favored over ketene acetals. | 0 | Organic Reactions |
adopts an unusual “extreme cradle” structure, with D point group symmetry. It can be viewed as a derivative of a (hypothetical) eight-membered ring (or more simply a deformed eight-membered ring) of alternating sulfur and nitrogen atoms. The pairs of sulfur atoms across the ring are separated by 2.586 Å, resulting in a cage-like structure as determined by single crystal X-ray diffraction. The nature of the transannular S–S interactions remains a matter of investigation because it is significantly shorter than the sum of the van der Waal's distances but has been explained in the context of molecular orbital theory. One pair of the transannular S atoms have valence 4, and the other pair of the transannular S atoms have valence 2. The bonding in is considered to be delocalized, which is indicated by the fact that the bond distances between neighboring sulfur and nitrogen atoms are nearly identical. has been shown to co-crystallize with benzene and the fullerene| molecule. | 1 | Inorganic Reactions + Inorganic Compounds |
Macrocycles can access a number of stable conformations, with preferences to reside in those that minimize the number of transannular nonbonded interactions within the ring. Medium rings (8-11 atoms) are the most strained with between 9-13 (kcal/mol) strain energy; analysis of the factors important in considering larger macrocyclic conformations can thus be modeled by looking at medium ring conformations. Conformational analysis of odd-membered rings suggests they tend to reside in less symmetrical forms with smaller energy differences between stable conformations. | 0 | Organic Reactions |
Many analogues have been prepared from primary, secondary, and even tertiary amines:
* Borane tert-butylamine ()
* Borane trimethylamine ()
* Borane isopropylamine ()
The first amine adduct of borane was derived from trimethylamine. Borane tert-butylamine complex is prepared by the reaction of sodium borohydride with t-butylammonium chloride. Generally adduct are more robust with more basic amines. Variations are also possible for the boron component, although primary and secondary boranes are less common. | 1 | Inorganic Reactions + Inorganic Compounds |
Friedrich Wöhlers conversion of ammonium cyanate into urea in 1828 is often cited as the starting point of modern organic chemistry. In Wöhlers era, there was widespread belief that organic compounds were characterized by a vital spirit. In the absence of vitalism, the distinction between inorganic and organic chemistry is merely semantic. | 1 | Inorganic Reactions + Inorganic Compounds |
Glycosylation is the reaction in which a carbohydrate (or glycan), i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule (a glycosyl acceptor) in order to form a glycoconjugate. In biology (but not always in chemistry), glycosylation usually refers to an enzyme-catalysed reaction, whereas glycation (also non-enzymatic glycation and non-enzymatic glycosylation) may refer to a non-enzymatic reaction.
Glycosylation is a form of co-translational and post-translational modification. Glycans serve a variety of structural and functional roles in membrane and secreted proteins. The majority of proteins synthesized in the rough endoplasmic reticulum undergo glycosylation. Glycosylation is also present in the cytoplasm and nucleus as the O-GlcNAc modification. Aglycosylation is a feature of engineered antibodies to bypass glycosylation. Five classes of glycans are produced:
* N-linked glycans attached to a nitrogen of asparagine or arginine side-chains. N-linked glycosylation requires participation of a special lipid called dolichol phosphate.
* O-linked glycans attached to the hydroxyl oxygen of serine, threonine, tyrosine, hydroxylysine, or hydroxyproline side-chains, or to oxygens on lipids such as ceramide.
* Phosphoglycans linked through the phosphate of a phosphoserine.
*C-linked glycans, a rare form of glycosylation where a sugar is added to a carbon on a tryptophan side-chain. Aloin is one of the few naturally occurring substances.
* Glypiation, which is the addition of a GPI anchor that links proteins to lipids through glycan linkages. | 0 | Organic Reactions |
Fluoroantimonic acid is formed by combining hydrogen fluoride and antimony pentafluoride:
:SbF + 2 HF + HF
The speciation (i.e., the inventory of components) of "fluoroantimonic acid" is complex. Spectroscopic measurements show that fluoroantimonic acid consists of a mixture of HF-solvated protons, [ (such as ), and SbF-adducts of fluoride, [(SbF)F] (such as ). Thus, the formula "" is a convenient but oversimplified approximation of the true composition. Nevertheless, the extreme acidity of this mixture is evident from the exceptionally poor proton-accepting ability of the species present in solution. Hydrogen fluoride, a weak acid in aqueous solution that is normally not thought to have any appreciable Brønsted basicity at all, is in fact the strongest Brønsted base in the mixture, protonating to HF in the same way water protonates to HO in aqueous acid. As a result, the acid is often said to contain "naked protons", though the "free" protons are, in fact, always bonded to hydrogen fluoride molecules. It is the fluoronium ion that accounts for fluoroantimonic acid's extreme acidity. The protons easily migrate through the solution, moving from HF to HF, when present, by the Grotthuss mechanism.
Two related products have been crystallized from HF-SbF mixtures, and both have been analyzed by single crystal X-ray crystallography. These salts have the formulas and . In both salts, the anion is . As mentioned above, is weakly basic; the larger anion is expected to be a still weaker base. | 1 | Inorganic Reactions + Inorganic Compounds |
The vapor of cesium metaborate has neutral monomers and dimers as well as ionized versions thereof. The same situation holds for thallium metaborate . | 1 | Inorganic Reactions + Inorganic Compounds |
Other methods available for the preparation of 2,3-epoxy alcohols have the advantage that they do not begin with an existing 2,3-epoxy alcohol; however, they tend to involve more steps than epoxide migration. Asymmetric dihydroxylation may be used to synthesize epoxy alcohols with high stereoselectivity, and some of the methods relying on dihydroxylation avoid the use of strongly basic conditions.
An alternative method that leads to retention of configuration at C-2 involves mesylation of an epoxy alcohol, epoxide opening, and re-closing by displacement of the mesylate. | 0 | Organic Reactions |
A hydrogen on the α position of a carbonyl compound is weakly acidic and can be removed by a strong base to yield an enolate ion. In comparing acetone (pK= 19.3) with ethane (pK= 60), for instance, the presence of a neighboring carbonyl group increases the acidity of the ketone over the alkane by a factor of 10.
Abstraction of a proton from a carbonyl compound occurs when the a C-H bond is oriented roughly parallel to the p orbitals of the carbonyl group. The α carbon atom of the enolate ion is sp-hybridized and has a p orbital that overlaps the neighboring carbonyl p orbitals. Thus, the negative charge is shared by the electronegative oxygen atom, and the enolate ion is stabilized by resonance.
Carbonyl compounds are more acidic than alkanes for the same reason that carboxylic acids are more acidic than alcohols. In both cases, the anions are stabilized by resonance. Enolate ions differ from carboxylate ions, however, in that their two resonance forms are not equivalent- the form with the negative charge on oxygen is lower in energy than the form with the charge on carbon. Nevertheless, the principle behind resonance stabilization is the same in both cases.
Because carbonyl compounds are only weakly acidic, a strong base is needed for enolate ion formation . If an alkoxide such as sodium ethoxide is used as base, deprotonation takes place only to the extent of about 0.1% because acetone is a weaker acid than ethanol (pK= 16). If, however, a more powerful base such as sodium hydride (NaH) or lithium diisopropylamide (LDA) is used, a carbonyl compound can be completely converted into its enolate ion. Lithium diisopropylamide (LDA), which is easily prepared by reaction of the strong base butyllithium with diisopropylamine, is widely used in the laboratory as a base for preparing enolate ions from carbonyl compounds.
Many types of carbonyl compounds, including aldehydes, ketones, esters, thioesters, acids, and amides, can be converted into enolate ions by reaction with LDA. Note that nitriles, too, are acidic and can be converted into enolate-like anions (referred to as nitrile anions).
When a hydrogen atom is flanked by two carbonyl groups, its acidity is enhanced even more. This enhanced acidity of β-dicarbonyl compounds is due to the stabilization of the resultant enolate ions by delocalization of the negative charge over both carbonyl groups. | 0 | Organic Reactions |
Vicinal difunctionalization refers to a chemical reaction involving transformations at two adjacent centers (most commonly carbons). This transformation can be accomplished in α,β-unsaturated carbonyl compounds via the conjugate addition of a nucleophile to the β-position followed by trapping of the resulting enolate with an electrophile at the α-position. When the nucleophile is an enolate and the electrophile a proton, the reaction is called Michael addition. | 0 | Organic Reactions |
On an industrial scale, barium chloride is prepared via a two step process from barite (barium sulfate). The first step requires high temperatures.
The second step requires reaction between barium sulfide and hydrogen chloride:
or between barium sulfide and calcium chloride:
In place of HCl, chlorine can be used. Barium chloride is extracted out from the mixture with water. From water solutions of barium chloride, its dihydrate () can be crystallized as colorless crystals.
Barium chloride can in principle be prepared by the reaction between barium hydroxide or barium carbonate with hydrogen chloride. These basic salts react with hydrochloric acid to give hydrated barium chloride. | 1 | Inorganic Reactions + Inorganic Compounds |
Early explanations for the deep red color of the salt were attributed to the special structure of the crystal lattice, albeit with little explanation. While Drew & Tess attempted to explain the deep color of this compound based on the assumption of a Pt(III) species, Jensen established the diamagnetism of the compound and proved that it did not involve Pt(III). Spectrochemical studies on the compound crystals concluded that the deep color of Wolffram’s salt crystals is due to the stacking of the “infinite chains” - linear Pt(II)/Pt(IV) stacked on top of each other.
In 1960, the crystal structure was shown to be consistent with the formulated double salt, inspiring examinations of other analogues to compare and better understand this unique coordination pattern.
Solid-state physical examinations were conducted to further elucidate the charge transfer across the mixed valence chain and potentially find use as semiconductors. X-ray scattering studies were performed, explicitly showing the mixed valence chain structure. Optical properties were probed, as well as potential use as a photocatalyst, albeit with disappointing results. | 1 | Inorganic Reactions + Inorganic Compounds |
In Nahuatl, the language of the Aztecs, the word for calcium hydroxide is nextli. In a process called nixtamalization, maize is cooked with nextli to become , also known as hominy. Nixtamalization significantly increases the bioavailability of niacin (vitamin B3), and is also considered tastier and easier to digest. Nixtamal is often ground into a flour, known as masa, which is used to make tortillas and tamales.
In chewing coca leaves, calcium hydroxide is usually chewed alongside to keep the alkaloid stimulants chemically available for absorption by the body. Similarly, Native Americans traditionally chewed tobacco leaves with calcium hydroxide derived from burnt mollusc shells to enhance the effects. It has also been used by some indigenous American tribes as an ingredient in yopo, a psychedelic snuff prepared from the beans of some Anadenanthera species. | 1 | Inorganic Reactions + Inorganic Compounds |
Diimide reductions result in the syn addition of dihydrogen to alkenes and alkynes. This observation has led to the proposal that the mechanism involves concerted hydrogen transfer from cis-diimide to the substrate. The cis isomer is the less stable of the two; however, acid catalysis may speed up equilibration of the trans and cis isomers.
Diimide is typically generated either through the oxidation of hydrazine or the decarboxylation of potassium azodicarboxylate. Kinetic experiments suggest that regardless of its method of generation, the formation of diimide is rate-limiting. The transition state of the hydrogen transfer step is likely early; however, high stereoselectivity has been obtained in many reductions of chiral alkenes.
The order of reactivity of unsaturated substrates is: alkynes, allenes > terminal or strained alkenes > substituted alkenes. Trans alkenes react more rapidly than cis alkenes in general. The reactivity difference between alkynes and alkenes is usually not great enough to isolate intermediate alkenes; however, alkenes can be isolated from allene reductions.
Diimide reduces symmetrical double bonds i.e.,C=C. N=N, O=O etc. unsymmetrical double bonds can not be reduced | 0 | Organic Reactions |
GaN nanotubes and nanowires are proposed for applications in nanoscale electronics, optoelectronics and biochemical-sensing applications. | 1 | Inorganic Reactions + Inorganic Compounds |
Sodium iodide activated with thallium, NaI(Tl), when subjected to ionizing radiation, emits photons (i.e., scintillate) and is used in scintillation detectors, traditionally in nuclear medicine, geophysics, nuclear physics, and environmental measurements. NaI(Tl) is the most widely used scintillation material. The crystals are usually coupled with a photomultiplier tube, in a hermetically sealed assembly, as sodium iodide is hygroscopic. Fine-tuning of some parameters (i.e., radiation hardness, afterglow, transparency) can be achieved by varying the conditions of the crystal growth. Crystals with a higher level of doping are used in X-ray detectors with high spectrometric quality. Sodium iodide can be used both as single crystals and as polycrystals for this purpose. The wavelength of maximum emission is 415 nm. | 1 | Inorganic Reactions + Inorganic Compounds |
Intramolecular cyclopropanation of a diazoketone is applied in a racemic synthesis of sirenin. A single cyclopropane diastereomer was isolated in 55% yield after diazoketone formation and cyclization. | 0 | Organic Reactions |
Iodides (including sodium iodide) are detectably oxidized by atmospheric oxygen (O) to molecular iodine (I). I and I complex to form the triiodide complex, which has a yellow color, unlike the white color of sodium iodide. Water accelerates the oxidation process, and iodide can also produce I by photooxidation, therefore for maximum stability sodium iodide should be stored under dark, low temperature, low humidity conditions. | 1 | Inorganic Reactions + Inorganic Compounds |
The equilibrium of this reaction shows a significant temperature dependence and the equilibrium constant decreases with an increase in temperature, that is, higher hydrogen formation is observed at lower temperatures. | 1 | Inorganic Reactions + Inorganic Compounds |
Vanadates exhibit a variety of biological activities, in part because they serve as structural mimics of phosphates. It acts as a competitive inhibitor of ATPases, alkaline and acid phosphatases, and protein-phosphotyrosine phosphatases, and its inhibitory effects can be reversed by dilution or the addition of ethylenediaminetetraacetic acid (EDTA).
Orthovanadate is activated by boiling and adjusting pH to ~10; this depolymerizes decavanadate into the active inhibitor, monovanadate. | 1 | Inorganic Reactions + Inorganic Compounds |
Sodium orthovanadate is produced by dissolving vanadium(V) oxide in a solution of sodium hydroxide:
The salt features tetrahedral anion centers linked to octahedral cation sites. | 1 | Inorganic Reactions + Inorganic Compounds |
Many low-valent and electron-rich transition metals effect stoichiometric dehalogenation. The reaction achieves practical interest in the context of organic synthesis, e.g. Cu-promoted Ullmann coupling.
The reaction is mainly conducted as stoichiometrically. Some metalloenzymes Vitamin B12 and coenzyme F430 are capable of dehalogenations catalytically. Of great interest are hydrodehalogenations, especially for chlorinated precursors: | 0 | Organic Reactions |
Hydrazines and hydroxylamines displace carbonyl oxygens much more readily than amines. Their equilibria strongly favor the dehydrated product, and the carbonyl is recovered only with difficulty. | 0 | Organic Reactions |
The mechanism involves the addition of amine to dichlorocarbene, a reactive intermediate generated by the dehydrohalogenation of chloroform. Two successive base-mediated dehydrochlorination steps result in formation of the isocyanide. | 0 | Organic Reactions |
"Ionic" metal halides (predominantly of the alkali and alkali earth metals) tend to have very high melting and boiling points. They freely dissolve in water, and some are deliquescent. They are generally poorly soluble in organic solvents.
Some low-oxidation state transition metals have halides which dissolve well in water, such as ferrous chloride, nickelous chloride, and cupric chloride. Metal cations with a high oxidation state tend to undergo hydrolysis instead, e.g. ferric chloride, aluminium chloride, and titanium tetrachloride.
Discrete metal halides have lower melting and boiling points. For example, titanium tetrachloride melts at −25 °C and boils at 135 °C, making it a liquid at room temperature. They are usually insoluble in water, but soluble in organic solvent.
Polymeric metal halides generally have melting and boiling points that are higher than monomeric metal halides, but lower than ionic metal halides. They are soluble only in the presence of a ligand which liberates discrete units. For example, palladium chloride is quite insoluble in water, but it dissolves well in concentrated sodium chloride solution:
:PdCl (s) + 2 Cl (aq) → PdCl (aq)
Palladium chloride is insoluble in most organic solvents, but it forms soluble monomeric units with acetonitrile and benzonitrile:
:[PdCl] + 2n CHCN → n PdCl(CHCN)
The tetrahedral tetrahalides of the first-row transition metals are prepared by addition of a quaternary ammonium chloride to the metal halide in a similar manner:
:MCl + 2 EtNCl → (EtN)MCl (M = Mn, Fe, Co, Ni, Cu)
Antimony pentafluoride is a strong Lewis acid. It gives fluoroantimonic acid, the strongest known acid, with hydrogen fluoride. Antimony pentafluoride as the prototypical Lewis acid, used to compare different compounds' Lewis basicities. This measure of basicity is known as the Gutmann donor number. | 1 | Inorganic Reactions + Inorganic Compounds |
The Buchner–Curtius–Schlotterbeck reaction is the reaction of aldehydes or ketones with aliphatic diazoalkanes to form homologated ketones. It was first described by Eduard Buchner and Theodor Curtius in 1885 and later by Fritz Schlotterbeck in 1907. Two German chemists also preceded Schlotterbeck in discovery of the reaction, Hans von Pechmann in 1895 and Viktor Meyer in 1905. The reaction has since been extended to the synthesis of β-keto esters from the condensation between aldehydes and diazo esters. The general reaction scheme is as follows:
The reaction yields two possible carbonyl compounds (I and II) along with an epoxide (III). The ratio of the products is determined by the reactant used and the reaction conditions. | 0 | Organic Reactions |
Aerated solutions of Cr(CHCN)(NS) are highly photoactive and prone to rapid decomposition. Deaerated solutions of Cr(CHCN)(NS) in acetonitrile are stable as long as they are kept in the dark. Continuous photolysis using 366 nm light is slow, while using a 355 nm pulsed laser results in faster labilization of NS. | 1 | Inorganic Reactions + Inorganic Compounds |
The Leuckart thiophenol reaction is the decomposition of a diazoxanthate, by gentle warming in a slightly acidic cuprous medium, to its corresponding aryl xanthates which give aryl thiols on alkaline hydrolysis and aryl thioethers on further warming.
This reaction was first reported by Rudolf Leuckart in 1890. | 0 | Organic Reactions |
The mechanism of the Kröhnke pyridine synthesis begins with enolization of α-pyridinium methyl ketone 4 followed by 1,4-addition to the α, β-unsaturated ketone 5 to form the Michael adduct 6, which immediately tautomerizes to the 1,5-dicarbonyl 7. Addition of ammonia to 7 followed by dehydration via 8 generates the imine intermediate 9., The imine intermediate is then deprotonated to enamine 10 and cyclizes with the carbonyl to generate intermediate 11. The pyridinium cation is then eliminated to form hydroxy-dienamine 12. Aromatization of 12 via subsequent loss of water generates the desired pyridine heterocycle 13. | 0 | Organic Reactions |
MIF with Borazocine linker was developed for hydrogen storage. Cu2I2Se6 has Se6 linkers. There are many MIFs with pnictogen linkers. | 1 | Inorganic Reactions + Inorganic Compounds |
Lanthanum hydroxide does not react much with alkaline substances, however is slightly soluble in acidic solution. In temperatures above 330 °C it decomposes into lanthanum oxide hydroxide (LaOOH), which upon further heating decomposes into lanthanum oxide ():
: LaOOH
:2 LaOOH
Lanthanum hydroxide crystallizes in the hexagonal crystal system. Each lanthanum ion in the crystal structure is surrounded by nine hydroxide ions in a tricapped trigonal prism. | 1 | Inorganic Reactions + Inorganic Compounds |
Enzymes, which are composed of chiral amino acids, catalyze chemical reactions with high stereoselectivity. Specifically, esterase enzymes catalyze the hydrolysis of esters to carboxylic acids. This transformation may be rendered asymmetric if two enantiotopic ester groups exist in the substrate or if a racemic mixture of chiral esters is used. In the former case (desymmetrization), the chiral environment of the enzyme active site leads to selective hydrolysis of the ester that is closer to the catalytically active serine residue when the substrate is bound to the enzyme. In the latter case (kinetic resolution), one of the enantiomers is hydrolyzed faster than the other, leading to an excess of hydrolyzed product from one enantiomer. Both strategies rely on the fact that the transition states for hydrolysis of enantiotopic or enantiomorphic ester groups by the chiral enzyme are diastereomeric.
Pig liver esterase (PLE) is a widely used enzyme for asymmetric ester hydrolysis. Although it was originally used for the desymmetrizing hydrolysis of glutarate esters, PLE also hydrolyzes malonates, cyclic diesters, monoesters, and other substrates. Active site models have been advanced to explain the selectivity of PLE. | 0 | Organic Reactions |
Gene expression is regulated by histone acetylation and deacetylation, and this regulation is also applicable to inflammatory genes. Inflammatory lung diseases are characterized by expression of specific inflammatory genes such as NF-κB and AP-1 transcription factor. Treatments with corticosteroids and theophylline for inflammatory lung diseases interfere with HAT/HDAC activity to turn off inflammatory genes.
Specifically, gene expression data demonstrated increased activity of HAT and decreased level of HDAC activity in patients with Asthma. Patients with chronic obstructive pulmonary disease showed there is an overall decrease in HDAC activity with unchanged levels of HAT activity. Results have shown that there is an important role for HAT/HDAC activity balance in inflammatory lung diseases and provided insights on possible therapeutic targets. | 0 | Organic Reactions |
The basic mechanism of the Payne rearrangement involves deprotonation of the free hydroxyl group, invertive nucleophilic attack on the proximal epoxide carbon, and re-protonation of the newly freed alkoxide. Each step of the process is reversible.
Several observations suggest that this mechanistic picture is oversimplified. Epoxide migration either does not occur or is very sluggish under aprotic conditions—it has been suggested that nucleophilic attack is slowed by the coordination of metal ions to the nucleophilic oxygen under aprotic conditions. In addition, when an external nucleophile is added to equilibrating epoxide isomers, the ratio of opened products does not reflect the ratio of epoxide isomers in solution or their relative thermodynamic stability. In situ nucleophilic opening of equilibrating epoxides is an example of Curtin-Hammett conditions—because the epoxides are equilibrating rapidly relative to the rate of epoxide opening, it is the kinetic barriers of ring opening that control the observed product ratio. In the example below, the product of opening of the terminal epoxide is the major product, even though the terminal epoxide itself is less thermodynamically stable than the internal isomer.
Halo diols may be used as precursors to 2,3-epoxy alcohols prior to rearrangement. Issues of site selectivity may arise if the two hydroxyl groups flanking the halide are not equivalent. In general, the formation of internal, substituted epoxides is more rapid than the formation of terminal epoxides. This idea can be used to predict the course of migrations of in situ-generated epoxides. | 0 | Organic Reactions |
To effect dual activation by a single metal, the same metal species that activates the enolate also interacts with the alkyne. Though the precise mechanisms are poorly understood and likely vary from case to case, metals such as In, Zn, Fe, and Cu are proposed to operate via this mode. One reaction system thought to proceed via one-metal dual activation is that developed by Shaw et al. in 2014. Using a catalytic Fe(III)-(Salen) complex, Shaw and coworkers were able to access chiral cyclopentanes from an array of alkynyl-tethered β-ketoesters and analogs thereof. The reaction tolerated a wide range of ketones (phenyl, homoallyl, cyclopropyl, 2-furyl, etc.), esters (ethyl, tert-butyl, etc.), and ester analogs (nitro, , cyano, sulfonyl, etc.). | 0 | Organic Reactions |
Deprotonation of enolizable ketones, aromatic alcohols, aldehydes, and esters gives enolates. With strong bases, the deprotonation is quantitative. Typically enolates are generated from using lithium diisopropylamide (LDA).
Often, as in conventional Claisen condensations, Mannich reactions, and aldol condensations, enolates are generated in low concentrations with alkoxide bases. Under such conditions, they exist in low concentrations, but they still undergo reactions with electrophiles. Many factors affect the behavior of enolates, especially the solvent, additives (e.g. diamines), and the countercation (Li vs Na, etc.). For unsymmetrical ketones, methods exist to control the regiochemistry of the deprotonation.
The deprotonation of carbon acids can proceed with either kinetic or thermodynamic reaction control. For example, in the case of phenylacetone, deprotonation can produce two different enolates. LDA has been shown to deprotonate the methyl group, which is the kinetic course of the deprotonation. To ensure the production of the kinetic product, a slight excess (1.1 equiv) of lithium diisopropylamide is used, and the ketone is added to the base at −78 °C. Because the ketone is quickly and quantitatively converted to the enolate and base is present in excess at all times, the ketone is unable to act as a proton shuttle to catalyze the gradual formation of the thermodynamic product. A weaker base such as an alkoxide, which reversibly deprotonates the substrate, affords the more thermodynamically stable benzylic enolate.
Enolates can be trapped by acylation and silylation, which occur at oxygen. Silyl enol ethers are common reagents in organic synthesis as illustrated by the Mukaiyama aldol reaction: | 0 | Organic Reactions |
Cyclobutenone was originally synthesized from the 3-bromocyclobutanone and 3-chlorocyclobutanone precursors which were prepared from an allene and a ketene via two independent routes. Scheme 7 shows the preparation from cyclobutenone from an allene.
Activated alkyoxyacetylenes can be synthesized in a single-pot preparation of triisopropylsilyloxyacetylenes from esters. The silyloxyacetylenes are useful substitutes for alkoxyacetylenes in [2 + 2] cycloaddition reactions with ketenes and vinylketenes affording cyclobutenones (Scheme 8).
Diazoketones can be synthesized in one-step from readily available ketones or carboxylic acid precursors by the addition of diazomethane to acyl chlorides. A diazo group transfer method can be used to produce α,β-unsaturated ketones. The traditional method of the deformylative diazo transfer approach has been improved upon by substituting the trifluoroacetylation of generated lithium enolates for the Claisen formylation step. The key step in this procedure is activation of the ketone starting material to the corresponding α-trifluoroacetyl derivative using trifluoroethyltrifluoroacetate (TFEA) (Scheme 9).
Alkynes or ketenophiles can be synthesized by various methods. Trialkylsilyloxyalkynes have proven to be excellent ketenophiles. These alkynes react in the annulation reaction to form resorcinol monosilyl ethers which can be de-protected under mild reaction conditions.
Base-promoted dehydrohalogenation of (Z)-2-halovinyl ethers to form alkoxyacetylenes is one of the most well established routes of alkyne synthesis (Scheme 10).
The synthesized alkynes are then heated in benzene or toluene in presence of excess cyclobutenone initiating the benzannulation reaction. Treatment with n-BuNF in tetrahydrofuran removes the siloxy groups to form the desired diols. | 0 | Organic Reactions |
A variety of methods for the generation of diimide exist. The most synthetically useful methods are:
* Oxidation of hydrazine with oxygen, in the presence of a copper(II) catalyst and/or a carboxylic acid
* Decarboxylation of dipotassium azodicarboxylate in the presence of an acid
* Thermal decomposition of sulfonylhydrazides
Procedures (particularly those employing air as an oxidant) are typically straightforward and do not require special handling techniques. | 0 | Organic Reactions |
For this purpose an optical fiber tip of an optical fiber temperature sensor is equipped with a gallium arsenide crystal. Starting at a light wavelength of 850 nm GaAs becomes optically translucent. Since the spectral position of the band gap is temperature dependent, it shifts about 0.4 nm/K. The measurement device contains a light source and a device for the spectral detection of the band gap. With the changing of the band gap, (0.4 nm/K) an algorithm calculates the temperature (all 250 ms). | 1 | Inorganic Reactions + Inorganic Compounds |
Imine hydrogenation provides a practical route to chiral amines.
Metolachlor is the active ingredient in the widely used herbicide Dual Magnum. A key step in its industrial production involves the enantioselective reduction of an N-aryl imine. This reduction is achieved with extremely high turnover number (albeit moderate enantioselectivity) through the use of a specialized catalyst system consisting of [Ir(COD)Cl], modified Josiphos ligand 3, and acid and iodide additives. | 0 | Organic Reactions |
Since directing groups are ligands, their effectiveness correlates with their affinities for metals. Common functional groups such as ketones usually are only weak ligands and thus often are poor DGs. This problem is solved by the use of a transient directing group. Transient DGs reversibly convert weak DGs (e.g., ketones) into strong DG's (e.g., imines) via a Schiff base condensation. Subsequent to serving their role as DGs, the imine can hydrolyze, regenerating the ketone and amine. | 0 | Organic Reactions |
The Kröhnke methodology has also been utilized to generate a number of interesting metal-binding ligands since polypyridyl complexes such as bipyridine (bipy) have been used extensively as ligands. The Kröhnke synthesis was used to prepare a family of tetrahydroquinoline-based N, S-type ligands. 2-thiophenylacetophenone (36) was reacted with iodine gas and pyridine in quantitative yield to generate acylmethylpyridinium iodide 37. Reaction with a chiral cyclic α, β-unsaturated ketone derived from 2-(+)-carene yielded the desired N, S-type ligand 38.
Novel, chiral P, N-ligands have been prepared using the Kröhnke method. α-pyridinium acyl ketone salt 39 was cyclized with pinocarvone derivative 40 to generate pyridine 41. The benzylic position of 41 was methylated and subsequent SnAr reaction with potassium diphenylphosphide to generate ligand 42.
The Kröhnke reaction has also enjoyed applicability to the synthesis of a number of biologically active compounds in addition to ones cataloged in combinatorial studies. Kelly and co-workers developed a route to cyclo-2,2′:4′,4′′:2′′,2′′′:4′′′,4′′′′:2′′′′,2′′′′′:4′′′′′,4-sexipyridine utilizing the Kröhnke reactions as the key macrocyclization step. Polypyridine complex 43 was treated with N-Bromosuccinimide in wet tetrahydrofuran followed by pyridine to generate the acylmethylpyridinium salt 44 which can then undergo the macrocyclization under standard conditions to yield the desired product 45. The Kröhnke method in this synthesis was crucial due to the failure of other cyclization techniques such as the Glaser coupling or Ullmann coupling.
Another use of the Kröhnke pyridine synthesis was the generation of a number of 2,4,6-trisubstituted pyridines that were investigated as potential topoisomerase 1 inhibitors. 2-acetylthiophene (46) was treated with iodine and pyridine to generate α-pyridinium acyl ketone 47. Reaction with Michael acceptor 48 under standard conditions yielded functionalized pyridine 49 in 60% overall yield.
Ultimately, the Kröhnke pyridine synthesis offers a facile and straightforward approach to the synthesis of a wide breadth of functionalized pyridines and poly aryl systems. The Kröhnke methodology has been applied to a number of strategies towards interesting ligands and biologically relevant molecules. Additionally, the Kröhnke reaction and its variations offer a number of advantages than alternative methods to pyridine synthesis ranging from one-pot, organic solvent-free variations to high atom economy. | 0 | Organic Reactions |
Sodium hydroxide was first prepared by soap makers. A procedure for making sodium hydroxide appeared as part of a recipe for making soap in an Arab book of the late 13th century: (Inventions from the Various Industrial Arts), which was compiled by al-Muzaffar Yusuf ibn Umar ibn Ali ibn Rasul (d. 1295), a king of Yemen. The recipe called for passing water repeatedly through a mixture of alkali (Arabic: , where is ash from saltwort plants, which are rich in sodium; hence alkali was impure sodium carbonate) and quicklime (calcium oxide, CaO), whereby a solution of sodium hydroxide was obtained. European soap makers also followed this recipe. When in 1791 the French chemist and surgeon Nicolas Leblanc (1742–1806) patented a process for mass-producing sodium carbonate, natural "soda ash" (impure sodium carbonate that was obtained from the ashes of plants that are rich in sodium) was replaced by this artificial version. However, by the 20th century, the electrolysis of sodium chloride had become the primary method for producing sodium hydroxide. | 1 | Inorganic Reactions + Inorganic Compounds |
A metaborate is a borate anion consisting of boron and oxygen, with empirical formula . Metaborate also refers to any salt or ester of such anion (e.g. salts such as sodium metaborate or calcium metaborate , and esters such as methyl metaborate ). Metaborate is one of the boron's oxyanions. Metaborates can be monomeric, oligomeric or polymeric.
In aqueous solutions metaborate anion hydrolyzes to tetrahydroxyborate . For this reason, solutions or hydrated salts of the latter are often improperly named "metaborates". | 1 | Inorganic Reactions + Inorganic Compounds |
Indium(III) hydroxide is the chemical compound with the formula . Its prime use is as a precursor to indium(III) oxide, . It is sometimes found as the rare mineral dzhalindite.
__TOC__ | 1 | Inorganic Reactions + Inorganic Compounds |
Shang et al. discovered the decarboxylative coupling of potassium oxalate monoesters with aryl halides to obtain aryl or alkenyl esters. | 0 | Organic Reactions |
N-demethylation of 3° amines is by the von Braun reaction, which uses BrCN as the reagent to give the corresponding nor- derivatives. A modern variation of the von Braun reaction was developed, where BrCN was superseded by ethyl chloroformate. The preparation of Paxil from arecoline is an application of this reaction, as well as the synthesis of GSK-372,475, for example.
The N-demethylation of imipramine gives desipramine. | 0 | Organic Reactions |
Barium azide may be prepared by reacting sodium azide with a soluble barium salt. Care should be taken to prevent large crystals from forming in the solution as barium azide crystals will explode if subjected to friction/shock or if fully dried. The product should be stored submerged in ethanol. | 1 | Inorganic Reactions + Inorganic Compounds |
Magnesium oxalate has been found naturally near Mill of Johnston, which is located close to Insch in northeast Scotland. This naturally occurring magnesium oxalate is called glushinskite and occurs at the lichen/rock interface on serpentinite as a creamy white layer mixed in with the hyphae of the lichen fungus. A scanning electron micrograph of samples taken showed that the crystals had a pyramidal structure with both curved and striated faces. The size of these crystals ranged from 2 to 5 μm. | 1 | Inorganic Reactions + Inorganic Compounds |
Bone ash is a material often used in cupellation, a process by which precious metals (such as gold and silver) are removed from base metals.
In cupellation, base metals in an impure sample are oxidized with the help of lead and are vaporized and absorbed into a porous cupellation material, typically made of magnesium or calcium. This leaves the precious metals which do not oxidize behind. Bone ash's extremely porous and calcareous structure as well as its high melting point makes it an ideal candidate for cupellation. | 1 | Inorganic Reactions + Inorganic Compounds |
Chiral auxiliaries on the alkene partner have been used for stereoselective transformations. In the reaction of camphorsultam-derived unsaturated amides, lower temperatures were needed to achieve high selectivities.
In reactions of silyl-substituted allylic acetates, chiral sulfoxides can be used to enforce high diastereofacial selectivity. | 0 | Organic Reactions |
Although inexpensive, barium chloride finds limited applications in the laboratory and industry.
Its main laboratory use is as a reagent for the gravimetric determination of sulfates. The sulfate compound being analyzed is dissolved in water and hydrochloric acid is added. When barium chloride solution is added, the sulfate present precipitates as barium sulfate, which is then filtered through ashless filter paper. The paper is burned off in a muffle furnace, the resulting barium sulfate is weighed, and the purity of the sulfate compound is thus calculated.
In industry, barium chloride is mainly used in the purification of brine solution in caustic chlorine plants and also in the manufacture of heat treatment salts, case hardening of steel. It is also used to make red pigments such as Lithol red and Red Lake C. Its toxicity limits its applicability. | 1 | Inorganic Reactions + Inorganic Compounds |
Demethylation often refers to cleavage of ethers, especially aryl ethers.
Historically, aryl methyl ethers, including natural products such as codeine (O-methylmorphine), have been demethylated by heating the substance in molten pyridine hydrochloride (melting point ) at , sometimes with excess hydrogen chloride, in a process known as the Zeisel–Prey ether cleavage. Quantitative analysis for aromatic methyl ethers can be performed by argentometric determination of the N-methylpyridinium chloride formed. The mechanism of this reaction starts with proton transfer from pyridinium ion to the aryl methyl ether, a highly unfavorable step (K ) that accounts for the harsh conditions required, given the much weaker acidity of pyridinium (pK = 5.2) compared to the protonated aryl methyl ether (an arylmethyloxonium ion, pK = –6.7 for aryl = Ph). This is followed by S2 attack of the arylmethyloxonium ion at the methyl group by either pyridine or chloride ion (depending on the substrate) to give the free phenol and, ultimately, N-methylpyridinium chloride, either directly or by subsequent methyl transfer from methyl chloride to pyridine.
Another classical (but, again, harsh) method for the removal of the methyl group of an aryl methyl ether is to heat the ether in a solution of hydrogen bromide or hydrogen iodide sometimes also with acetic acid. The cleavage of ethers by hydrobromic or hydroiodic acid proceeds by protonation of the ether, followed by displacement by bromide or iodide. A slightly milder set of conditions uses cyclohexyl iodide (CyI, 10.0 equiv) in N,N-dimethylformamide to generate a small amount of hydrogen iodide in situ.
Boron tribromide, which can be used at room temperature or below, is a more specialized reagent for the demethylation of aryl methyl ethers. The mechanism of ether dealkylation proceeds via the initial reversible formation of a Lewis acid-base adduct between the strongly Lewis acidic BBr and the Lewis basic ether. This Lewis adduct can reversibly dissociate to give a dibromoboryl oxonium cation and Br. Rupture of the ether linkage occurs through the subsequent nucleophilic attack on the oxonium species by Br to yield an aryloxydibromoborane and methyl bromide. Upon completion of the reaction, the phenol is liberated along with boric acid (HBO) and hydrobromic acid (aq. HBr) upon hydrolysis of the dibromoborane derivative during aqueous workup.
Stronger nucleophiles such as diorganophosphides (LiPPh) also cleave aryl ethers, sometimes under mild conditions. Other strong nucleophiles that have been employed include thiolate salts like EtSNa.
Aromatic methyl ethers, particularly those with an adjacent carbonyl group, can be regioselectively demethylated using magnesium iodide etherate. An example of this being used is in the synthesis of the natural product Calphostin A, as seen below.
Methyl esters also are susceptible to demethylation, which is usually achieved by saponification. Highly specialized demethylations are abundant, such as the Krapcho decarboxylation:
A mixture of anethole, KOH, and alcohol was heated in an autoclave. Although the product of this reaction was the expected anol, a highly reactive dimerization product in the mother liquors called dianol was also discovered by Charles Dodds. | 0 | Organic Reactions |
Modified aldol tandem reaction is a sequential chemical transformation that combines aldol reaction with other chemical reactions that generate enolates. Enolates are a common building block in chemical syntheses and are typically formed by the addition of base to a ketone or aldehyde. Modified Aldol tandem reactions allow similar reactivity to be produced without the need for a base which may have adverse effects in a given chemical synthesis. A representative example is the decarboxylative aldol reaction (Figure "Modified aldol tandem reaction, decarboxylative aldol reaction as an example"), where the enolate is generated via decarboxylation reaction mediated by either transition metals or organocatalysts. Key advantage of this reaction over other types of aldol reaction is the selective generation of an enolate in the presence of aldehydes. This allows for the directed aldol reaction to produce a desired cross aldol.
Transition metals have been used to mediate the modified aldol tandem reaction. Allyl β-keto carboxylates can be used as substrate for palladium-mediated decarboxylative aldol reaction (Figure "Palladium-mediated decarboxylative aldol reaction with allyl β-keto carboxylates"). The allyl group can be removed by palladium, following decarboxylation reaction selectively generates the enolate at the β-keto group, which could further react with aldehyde to generate aldols.
Using decarboxylation reaction to generate enolate is a common strategy in biosynthetic pathways such as polyketide synthesis, where malonic acid half thioester can be converted to the corresponding enolate for Claisen condensation reaction. Inspired by this, a modified tandem aldol reaction has been developed using the malonic acid half thioester as the enolate source. A copper based catalyst system has been developed for efficient aldol generation at mild conditions (Figure "Decarboxylative aldol reaction with malonic acid half thioester"). | 0 | Organic Reactions |
Catalysts for the lower temperature WGS reaction are commonly based on copper or copper oxide loaded ceramic phases, While the most common supports include alumina or alumina with zinc oxide, other supports may include rare earth oxides, spinels or perovskites. A typical composition of a commercial LTS catalyst has been reported as 32-33% CuO, 34-53% ZnO, 15-33% AlO. The active catalytic species is CuO. The function of ZnO is to provide structural support as well as prevent the poisoning of copper by sulfur. The AlO prevents dispersion and pellet shrinkage. The LTS shift reactor operates at a range of 200–250 °C. The upper temperature limit is due to the susceptibility of copper to thermal sintering. These lower temperatures also reduce the occurrence of side reactions that are observed in the case of the HTS. Noble metals such as platinum, supported on ceria, have also been used for LTS. | 1 | Inorganic Reactions + Inorganic Compounds |
These advancements have produced five main types of Conia-ene reactions characterized by the operative activation mode: namely, enolate, alkyne, or ene-yne activation, and one- or two-metal dual activation. Note that though the mechanisms of Conia-ene variants differ from the initial ene-like cyclization, they are still considered Conia-ene or Conia-ene-type reactions. In addition, due to the complexity of some Conia-ene reaction systems, the true mechanism may lay somewhere between several different activation modes. | 0 | Organic Reactions |
Seaborg Technologies is working on a nuclear reactor design in which NaOH is used as a neutron moderator. | 1 | Inorganic Reactions + Inorganic Compounds |
The peripheral attack model is based on predicting lowest energy conformations of an inherently complicated system, where nuanced perturbations can cause huge stereodifferentiating consequences. By modeling peripheral attack using the Curtin-Hammett scenario depicted above, the transition state is excluded from this conformation analysis by assuming that the barrier to each transition state from a given conformation is the same and thus that ground state conformations are the sole product determining factor. A significant criticism is the mapping of medium-sized ring conformations and influences onto larger ring systems. Macrocycles can possess varying degrees of rigidity in their structure, making a single peripheral attack model difficult to apply to all systems. Different classes of reactions might not fit the peripheral attack model, as reactions such as epoxidations, hydroxylations, alkylations, and reductions all proceed through different transition states. | 0 | Organic Reactions |
A solution of methyl(cyano)cuprate (Solution A) was prepared as follows: to a suspension of 0.35 g (3.91 mmol) of copper(I) cyanide in 5 mL of tetrahydrofuran under argon at 0° was added dropwise over about 5 minutes 2.76 mL of a solution of methyllithium in ethyl ether (1.4 M, 3.86 mmol). The colorless solution was stirred for 10 minutes at 0°, warmed to 25° over 30 minutes, then cooled again to 0°. Separately, a solution of the lithium salt of (±)-cis-4-benzyloxy-2,3-epoxy-1-butanol (Solution B) was prepared as follows: to a solution of 0.5 g (2.58 mmol) of the epoxy alcohol and 0.90 g (21.4 mmol) of lithium chloride in 10 mL of tetrahydrofuran under argon at −78° was added dropwise 1.65 mL of a solution of n-butyllithium in hexane (1.56 M, 2.58 mmol). The solution was stirred for 5 minutes at −78°, allowed to warm to 0°, and then stirred at that temperature for 10 minutes. The reaction was effected by the addition of Solution A to Solution B via cannula at 0° followed by warming to room temperature over 2 hours. The reaction mixture was then stirred for a further 12 hours and then cautiously treated with 5 mL of saturated aqueous ammonium chloride. The mixture was stirred for 1–2 hours to aid removal of copper residues. Ethyl ether (20 mL) was then added, and the organic layer was separated. The aqueous phase was extracted twice with 20 mL of ethyl ether, and the combined organic phases were dried over magnesium sulfate, filtered, and concentrated to give 0.51 g of the product as a colorless oil (95%), IR (film) 3400, 3100, 3060, 3030, 2970, 2930, 2870, 1600, 1500, 1465, 1445, 1385, 1370, 1320, 1285, 1210, 1180, 1120, 1100, 1075, 1030, 1020, 980, 905, 830, 750, 730, 710, 695 cm–1; 1H NMR (CDCl) δ 0.90 (t, J = 6.0 Hz, 3 H), 1.37–1.53 (m, 2 H), 3.20 (br s, 2 H), 3.40–3.65 (m, 4 H), 4.48 (s, 2 H), 7.29 (s, 5 H). | 0 | Organic Reactions |
Generally, nucleophilic epoxidations are carried out under inert atmosphere in anhydrous conditions. For zinc-mediated epoxidations, diethylzinc and ligand are first mixed and oxidized, then the enone is introduced. Lanthanide-mediated epoxidations typically require an additive to stabilize the catalyst; this is most commonly triphenylphosphine oxide or triphenylarsine oxide.
Phase-transfer catalyzed epoxidations may be carried out using one of three possible sets of reaction conditions: (1) sodium hypochlorite at room temperature, (2) freshly prepared 8 M potassium hypochlorite, or (3) trichloroisocyanuric acid in aqueous or non-aqueous conditions.
Among polypeptide-based methods, employing a phase transfer catalyst and triphasic media permits lower catalyst loadings. Biphasic conditions using an organic base in conjunction with urea/HO may also be used. | 0 | Organic Reactions |
The reaction of iron powder with o-nitrocinnamic acid reduces the nitro group to a nitroso. The nitrogen then condenses with a carbon on the alkene chain with loss of a molecule of water to form a ring. Decarboxylation gives indole. | 0 | Organic Reactions |
Because of its low toxicity and the mildness of its basic properties, slaked lime is widely used in the food industry:
* In USDA certified food production in plants and livestock
* To clarify raw juice from sugarcane or sugar beets in the sugar industry (see carbonatation)
* To process water for alcoholic beverages and soft drinks
* To increase the rate of Maillard reactions (pretzels)
* Pickle cucumbers and other foods
* To make Chinese century eggs
* In maize preparation: removes the cellulose hull of maize kernels (see nixtamalization)
* To clear a brine of carbonates of calcium and magnesium in the manufacture of salt for food and pharmaceutical uses
* In fortifying (Ca supplement) fruit drinks, such as orange juice, and infant formula
* As a substitute for baking soda in making papadam
* In the removal of carbon dioxide from controlled atmosphere produce storage rooms
* In the preparation of mushroom growing substrates | 1 | Inorganic Reactions + Inorganic Compounds |
The high stereospecificity and stereoselectivity inherent in many TMM cycloaddition reactions is a significant advantage; for instance, the trans ring junction in TMM cycloaddition adduct 2 was carried through in a synthesis of (+)-brefeldin A. | 0 | Organic Reactions |
DNA methylation is the conversion of the cytosine to 5-methylcytosine. The formation of Me-CpG is catalyzed by the enzyme DNA methyltransferase. In vertebrates, DNA methylation typically occurs at CpG sites (cytosine-phosphate-guanine sites—that is, sites where a cytosine is directly followed by a guanine in the DNA sequence). In mammals, DNA methylation is common in body cells, and methylation of CpG sites seems to be the default. Human DNA has about 80–90% of CpG sites methylated, but there are certain areas, known as CpG islands, that are CG-rich (high cytosine and guanine content, made up of about 65% CG residues), wherein none is methylated. These are associated with the promoters of 56% of mammalian genes, including all ubiquitously expressed genes. One to two percent of the human genome are CpG clusters, and there is an inverse relationship between CpG methylation and transcriptional activity. Methylation contributing to epigenetic inheritance can occur through either DNA methylation or protein methylation. Improper methylations of human genes can lead to disease development, including cancer.
In honey bees, DNA methylation is associated with alternative splicing and gene regulation based on functional genomic research published in 2013. In addition, DNA methylation is associated with expression changes in immune genes when honey bees were under lethal viral infection. Several review papers have been published on the topics of DNA methylation in social insects.
RNA methylation occurs in different RNA species viz. tRNA, rRNA, mRNA, tmRNA, snRNA, snoRNA, miRNA, and viral RNA. Different catalytic strategies are employed for RNA methylation by a variety of RNA-methyltransferases. RNA methylation is thought to have existed before DNA methylation in the early forms of life evolving on earth.
N6-methyladenosine (m6A) is the most common and abundant methylation modification in RNA molecules (mRNA) present in eukaryotes. 5-methylcytosine (5-mC) also commonly occurs in various RNA molecules. Recent data strongly suggest that m6A and 5-mC RNA methylation affects the regulation of various biological processes such as RNA stability and mRNA translation, and that abnormal RNA methylation contributes to etiology of human diseases.
In social insects such as honey bees, RNA methylation is studied as a possible epigenetic mechanism underlying aggression via reciprocal crosses. | 0 | Organic Reactions |
Conformational analysis of medium rings begins with examination of cyclooctane. Spectroscopic methods have determined that cyclooctane possesses three main conformations: chair-boat, chair-chair, and boat-boat. Cyclooctane prefers to reside in a chair-boat conformation, minimizing the number of eclipsing ethane interactions (shown in blue), as well as torsional strain. The chair-chair conformation is the second most abundant conformation at room temperature, with a ratio of 96:4 chair-boat:chair-chair observed.
Substitution positional preferences in the ground state conformer of methyl cyclooctane can be approximated using parameters similar to those for smaller rings. In general, the substituents exhibit preferences for equatorial placement, except for the lowest energy structure (pseudo A-value of -0.3 kcal/mol in figure below) in which axial substitution is favored. The "pseudo A-value" is best treated as the approximate energy difference between placing the methyl substituent in the equatorial or axial positions. The most energetically unfavorable interaction involves axial substitution at the vertex of the boat portion of the ring (6.1 kcal/mol).
These energetic differences can help rationalize the lowest energy conformations of 8 atom ring structures containing an sp center. In these structures, the chair-boat is the ground state model, with substitution forcing the structure to adopt a conformation such that non-bonded interactions are minimized from the parent structure. From the cyclooctene figure below, it can be observed that one face is more exposed than the other, foreshadowing a discussion of privileged attack angles (see peripheral attack).
X-ray analysis of functionalized cyclooctanes provided proof of conformational preferences in these medium rings. Significantly, calculated models matched the obtained X-ray data, indicating that computational modeling of these systems could in some cases quite accurately predict conformations. The increased sp character of the cyclopropane rings favor them to be placed similarly such that they relieve non-bonded interactions. | 0 | Organic Reactions |
Jiao et al. enabled the formation of a C–N bond via cross-coupling using air as an oxidant and a copper catalyst. No conditions are known for a C–N cross-coupling that breaks a sp or sp C–COOH bond. | 0 | Organic Reactions |
A transannular interaction in chemistry is any chemical interaction (favorable or nonfavorable) between different non-bonding molecular groups in a large ring or macrocycle. See for example atranes. | 0 | Organic Reactions |
Dioxirane epoxidation is highly versatile, and compares favorably to related peracid oxidations in many respects. Peracids generate acidic byproducts, meaning that acid-labile substrates and products must be avoided. Dioxirane epoxidations using isolated oxidant can be carried out under neutral conditions without the need for aqueous buffering. However, catalytic dioxirane oxidations do require water and are not suitable for hydrolytically unstable substrates.
Some methods are well-suited to the oxidation of electron-rich or electron-poor double bonds, but few are as effective for both classes of substrate as dioxiranes. Weitz-Scheffer conditions (NaOCl, HO/KOH, tBuOH/KOH) work well for oxidations of electron-poor double bonds, and sulfonyl-substituted oxaziridines are effective for electron-rich double bonds.
Metal-based oxidants are often more efficient than dioxirane oxidations in the catalytic mode; however, environmentally unfriendly byproducts are typically generated. In the realm of asymmetric methods, both the Sharpless epoxidation and Jacobsen epoxidation surpass asymmetric dioxirane oxidations in enantioselectivity. Additionally, enzymatic epoxidations are more enantioselective than dioxirane-based methods; however, operational difficulties and low yields are sometimes associated with enzymatic oxidations | 0 | Organic Reactions |
A classic example of transition metal-assisted dearomatization is the Buchner ring expansion. Catalytic asymmetric dearomatization reactions (CADA) are used in enantioselective synthesis. | 0 | Organic Reactions |
A glycosidase is an enzyme that catalyzes the breakdown of a glycosidic linkage to produce two smaller sugars. This process has important implications in the utilization of stored energy, like glycogen in animals, as well as in the breakdown of cellulose by organisms that feed on plants. In general, aspartic or glutamic acid residues in the active site of the enzyme catalyze the hydrolysis of the glycosidic bond. The mechanism of these enzymes involves an oxocarbenium ion intermediate, a general example of which is shown below. | 0 | Organic Reactions |
Enyne cycloisomerization, an alkyne variant of the Alder-ene reaction (figure 5), is an intramolecular rearrangement of 1,n–enynes to give the corresponding cyclic isomer.
Although the rearrangement may occur under thermal conditions, the scope of the thermal rearrangement is limited due to the requirement of high temperatures, thus transition metals such as Au, Pd, Pt, Rh and Ir are often employed as catalysts. As synthesis quarrels to build complex structural motifs in the presence of inductive, stereoelectronic and steric demands this rearrangement has recently been developed as a robust method for constructing carbo– and heterocyclic scaffolds with excellent chemo–, regio– and diastereoselective outcomes.
There is not a single mechanism that can be used to describe enyne cycloisomerizations as the mechanism depends on reaction conditions and catalyst selection. Intermediates of the metal catalyzed cycloisomerization in which the metal coordinates the alkyne or alkene activating either or both are possible and are shown in figure 6.
Activation of the alkyne by complexation with the metal leading to an η–metal intermediate such as 18 opens up the alkyne to nucleophilic attack and engenders carbocation intermediates. This Pull–push reactivity is important for understanding reactions mediated by π–acids. Complexation of the alkyne to the metal fragment depletes electron density in the bond (‘pull’), in concert with the ability of the metal to back donate (“push”) arouses the observed consecutive electrophilic and nucleophilic character to the vicinal carbon atoms of the alkyne (figure 7).
Metallacycle intermediates (19) are the result of the simultaneous complexation and activation of both partners. Hydrometallation of the alkyne giving a vinyl metal species that may in turn carbometalate the olefin is also possible (20). An example of a 1,6–enyne cycloisomerization proceeding through an η–activated metal intermediate is given in figure 8, which is common for enyne cycloisomerizations mediated by Pt or Au due to their π–acidic nature. Notably, in this example chirality transfer takes place in which the absolute stereochemistry of the enyne (26) controls stereochemistry of the product (27). | 0 | Organic Reactions |
Different transition metals have been used to catalyze carboamination reactions, including palladium, copper, and rhodium etc. The reaction mechanism varies with different transition metals. For palladium-catalyzed carboamination reactions, Pd(0)/Pd(II) and Pd(II)/Pd(IV) catalytic cycles are the most common mechanisms that have been proposed.
The reaction mode for the key aminopalladation step is different in these two cases. In Wolfe’s chemistry, which is known as the Pd(0)/Pd(II) catalytic system, syn-aminopalladation is observed. While in the Pd(II)/Pd(IV) catalytic system, which was developed by Forrest Michael, anti-aminopalladation was observed. It is believed that the pH of the reaction will affect the existing form of the amine nucleophile, which will determine whether the nitrogen coordinates with palladium center or not during the aminopalladation step. For the C–H activation step in Pd(II)/Pd(IV) chemistry, since there is no directing effect on the aromatic ring, large excess of arenes are required.
In 2015, Rovis and coworkers reported a rhodium-catalyzed intermolecular carboamination. In this reaction, enoxyphthalimide was used to serve as both the nitrogen and carbon source. The reaction mechanism is proposed in the paper (vide infra).
In 2017, Liu and coworkers reported a copper-catalyzed three component carboamination reaction of styrenes. In the meantime, Engle and coworkers published a palladium-catalyzed three component carboamination reaction using directing group strategy. These two works are the very rare examples of three component carboamination reactions. | 0 | Organic Reactions |
Zinc chloride is a common reagent in the laboratory useful Lewis acid in organic chemistry.
Molten zinc chloride catalyses the conversion of methanol to hexamethylbenzene:
Other examples include catalyzing (A) the Fischer indole synthesis, and also (B) Friedel-Crafts acylation reactions involving activated aromatic rings
Related to the latter is the classical preparation of the dye fluorescein from phthalic anhydride and resorcinol, which involves a Friedel-Crafts acylation. This transformation has in fact been accomplished using even the hydrated sample shown in the picture above.
Zinc chloride also activates benzylic and allylic halides towards substitution by weak nucleophiles such as alkenes:
In similar fashion, promotes selective sodium cyanoborohydride| reduction of tertiary, allylic or benzylic halides to the corresponding hydrocarbons.
Zinc chloride is also a useful starting reagent for the synthesis of many organozinc reagents, such as those used in the palladium catalyzed Negishi coupling with aryl halides or vinyl halides. In such cases the organozinc compound is usually prepared by transmetallation from an organolithium or a Grignard reagent, for example:
Zinc enolates, prepared from alkali metal enolates and , provide control of stereochemistry in aldol condensation reactions due to chelation on to the zinc. In the example shown below, the threo product was favored over the erythro by a factor of 5:1 when in DME/ether was used. The chelate is more stable when the bulky phenyl group is pseudo-equatorial rather than pseudo-axial, i.e., threo rather than erythro. | 1 | Inorganic Reactions + Inorganic Compounds |
Suggested by the idea that the structure of chromatin can be modified to allow or deny access of transcription activators, regulatory functions of histone acetylation and deacetylation can have implications with genes that cause other diseases. Studies on histone modifications may reveal many novel therapeutic targets.
Based on different cardiac hypertrophy models, it has been demonstrated that cardiac stress can result in gene expression changes and alter cardiac function. These changes are mediated through HATs/HDACs posttranslational modification signaling. HDAC inhibitor trichostatin A was reported to reduce stress induced cardiomyocyte autophagy. Studies on p300 and CREB-binding protein linked cardiac hypertrophy with cellular HAT activity suggesting an essential role of histone acetylation status with hypertrophy responsive genes such as GATA4, SRF, and MEF2.
Epigenetic modifications also play a role in neurological disorders. Deregulation of histones modification are found to be responsible for deregulated gene expression and hence associated with neurological and psychological disorders, such as Schizophrenia and Huntington disease. Current studies indicate that inhibitors of the HDAC family have therapeutic benefits in a wide range of neurological and psychiatric disorders. Many neurological disorders only affect specific brain regions; therefore, understanding of the specificity of HDACs is still required for further investigations for improved treatments. | 0 | Organic Reactions |
The Adams decarboxylation is a chemical reaction that involved the decarboxylation of coumarins which have carboxylic acid group in the third position. The decarboxylation is achieved by aqueous solution of sodium bisulfite, heat and a concentrated solution of sodium hydroxide. | 0 | Organic Reactions |
HCN is the precursor to sodium cyanide and potassium cyanide, which are used mainly in gold and silver mining and for the electroplating of those metals. Via the intermediacy of cyanohydrins, a variety of useful organic compounds are prepared from HCN including the monomer methyl methacrylate, from acetone, the amino acid methionine, via the Strecker synthesis, and the chelating agents EDTA and NTA. Via the hydrocyanation process, HCN is added to butadiene to give adiponitrile, a precursor to Nylon-6,6.
HCN is used globally as a fumigant against many species of pest insects that infest food production facilities. Both its efficacy and method of application lead to very small amounts of the fumigant being used compared to other toxic substances used for the same purpose. Using HCN as a fumigant also has minimal environmental impact, compared to similar structural fumigant molecules such as sulfuryl fluoride, and methyl bromide. | 1 | Inorganic Reactions + Inorganic Compounds |
Compounds of cobalt in the +3 oxidation state exist, such as cobalt(III) fluoride , nitrate , and sulfate ; however, cobalt(III) chloride is not stable in normal conditions, and would decompose immediately into and chlorine.
On the other hand, cobalt(III) chlorides can be obtained if the cobalt is bound also to other ligands of greater Lewis basicity than chloride, such as amines. For example, in the presence of ammonia, cobalt(II) chloride is readily oxidised by atmospheric oxygen to hexamminecobalt(III) chloride:
:4 ·6 + 4 Cl + 20 + → 4 + 26
Similar reactions occur with other amines. These reactions are often performed in the presence of charcoal as a catalyst, or with hydrogen peroxide substituted for atmospheric oxygen. Other highly basic ligands, including carbonate, acetylacetonate, and oxalate, induce the formation of Co(III) derivatives. Simple carboxylates and halides do not.
Unlike Co(II) complexes, Co(III) complexes are very slow to exchange ligands, so they are said to be kinetically inert. The German chemist Alfred Werner was awarded the Nobel prize in 1913 for his studies on a series of these cobalt(III) compounds, work that led to an understanding of the structures of such coordination compounds. | 1 | Inorganic Reactions + Inorganic Compounds |
Since its invention by Dr. John T. Gleaves (then at Monsanto Company) in late 1980s,
TAP has been used to study a variety of industrially and academically relevant catalytic reactions, bridging the gap between surface science
experiments and applied catalysis.
The state-of-the-art TAP installations (TAP-3) do not only provide better signal-to-noise ratio than the first generation TAP machines (TAP-1),
but also allow for advanced automation and direct coupling with other techniques. | 1 | Inorganic Reactions + Inorganic Compounds |