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Lead azide is highly sensitive and usually handled and stored under water in insulated rubber containers. It will explode after a fall of around 150 mm (6 in) or in the presence of a static discharge of 7 millijoules. Its detonation velocity is around .
Ammonium acetate and sodium dichromate are used to destroy small quantities of lead azide.
Lead azide has immediate deflagration to detonation transition (DDT), meaning that even small amounts undergo full detonation (after being hit by flame or static electricity).
Lead azide reacts with copper, zinc, cadmium, or alloys containing these metals to form other azides. For example, copper azide is even more explosive and too sensitive to be used commercially.
Lead azide was a component of the six .22 (5.6 mm) caliber Devastator rounds fired from a Röhm RG-14 revolver by John Hinckley, Jr. in his assassination attempt on U.S. President Ronald Reagan on March 30, 1981. The rounds consisted of lead azide centers with lacquer-sealed aluminum tips designed to explode upon impact. A strong probability exists that the bullet which struck White House press secretary James Brady in the head exploded. The remaining bullets that hit people, including the shot that hit President Reagan, did not explode. | 1 | Inorganic Reactions + Inorganic Compounds |
Magnesium oxalate is a skin and eye irritant. If inhaled, it will irritate the lungs and mucous membranes. Magnesium oxalate has no known chronic effects nor any carcinogenic effects. Magnesium oxalate is non-flammable and stable, but in fire conditions it will give off toxic fumes. According to OSHA, magnesium oxalate is considered to be hazardous. | 1 | Inorganic Reactions + Inorganic Compounds |
Ninhydrin reacts with amino acids and amines to form a colored compound "Ruhemann's purple" (RP). Spraying with a zinc chloride solution forms a 1:1 complex RP:, which is more readily detected as it fluoresces more intensely than RP. | 1 | Inorganic Reactions + Inorganic Compounds |
Boric acid reacts with alcohols to form borate esters, where R is alkyl or aryl. The reaction is typically driven by a dehydrating agent, such as concentrated sulfuric acid:
: + 3 ROH → + 3 | 1 | Inorganic Reactions + Inorganic Compounds |
In chemistry, disproportionation, sometimes called dismutation, is a redox reaction in which one compound of intermediate oxidation state converts to two compounds, one of higher and one of lower oxidation states. The reverse of disproportionation, such as when a compound in an intermediate oxidation state is formed from precursors of lower and higher oxidation states, is called comproportionation, also known as synproportionation.
More generally, the term can be applied to any desymmetrizing reaction where two molecules of one type react to give one each of two different types:
This expanded definition is not limited to redox reactions, but also includes some molecular autoionization reactions, such as the self-ionization of water. In contrast, some authors use the term redistribution to refer to reactions of this type (in either direction) when only ligand exchange but no redox is involved and distinguish such processes from disproportionation and comproportionation.<br />For example, the Schlenk equilibrium
is an example of a redistribution reaction. | 0 | Organic Reactions |
GaN dust is an irritant to skin, eyes and lungs. The environment, health and safety aspects of gallium nitride sources (such as trimethylgallium and ammonia) and industrial hygiene monitoring studies of MOVPE sources have been reported in a 2004 review.
Bulk GaN is non-toxic and biocompatible. Therefore, it may be used in the electrodes and electronics of implants in living organisms. | 1 | Inorganic Reactions + Inorganic Compounds |
The best Lewis structure for an oxocarbenium ion contains an oxygen–carbon double bond, with the oxygen atom attached to an additional group and consequently taking on a formal positive charge. In the language of canonical structures (or "resonance"), the polarization of the π bond is described by a secondary carbocationic resonance form, with a formal positive charge on carbon (see above). In terms of frontier molecular orbital theory, the Lowest Unoccupied Molecular Orbital (LUMO) of the oxocarbenium ion is a π* orbital that has the large lobe on the carbon atom; the more electronegative oxygen contributes less to the LUMO. Consequently, in an event of a nucleophilic attack, the carbon is the electrophilic site. Compared to a ketone, the polarization of an oxocarbenium ion is accentuated: they more strongly resemble a "true" carbocation, and they are more reactive toward nucleophiles. In organic reactions, ketones are commonly activated by the coordination of a Lewis acid or Brønsted acid to the oxygen to generate an oxocarbenium ion as an intermediate.
Numerically, a typical partial charge (derived from Hartree-Fock computations) for the carbonyl carbon of a ketone RC=O (like acetone) is δ+ = 0.51. With the addition of an acidic hydrogen to the oxygen atom to produce [RC=OH], the partial charge increases to δ+ = 0.61. In comparison, the nitrogen analogues of ketones and oxocarbenium ions, imines (RC=NR) and iminium ions ([RC=NRH]), respectively, have partial charges of δ+ = 0.33 and δ+ = 0.54, respectively. The order of partial positive charge on the carbonyl carbon is therefore imine < ketone < iminium < oxocarbenium.
This is also the order of electrophilicity for species containing C=X (X = O, NR) bonds. This order is synthetically significant and explains, for example, why reductive aminations are often best carried out at pH = 5 to 6 using sodium cyanoborohydride (Na[HB(CN)]) or sodium triacetoxyborohydride (Na[HB(OAc)]) as a reagent. Bearing an electron-withdrawing group, sodium cyanoborohydride and sodium triacetoxyborohydride are poorer reducing agents than sodium borohydride, and their direct reaction with ketones is generally a slow and inefficient process. However, the iminium ion (but not the imine itself) formed in situ during a reductive amination reaction is a stronger electrophile than the ketone starting material and will react with the hydride source at a synthetically useful rate. Importantly, the reaction is conducted under mildly acidic conditions that protonate the imine intermediate to a significant extent, forming the iminium ion, while not being strongly acidic enough to protonate the ketone, which would form the even more electrophilic oxocarbenium ion. Thus, the reaction conditions and reagent ensure that amine is formed selectively from iminium reduction, instead of direct reduction of the carbonyl group (or its protonated form) to form an alcohol. | 0 | Organic Reactions |
Bone ash is a white material produced by the calcination of bones. Typical bone ash consists of about 55.82% calcium oxide, 42.39% phosphorus pentoxide, and 1.79% water. The exact composition of these compounds varies depending upon the type of bones being used, but generally the formula for bone ash is Ca(OH)(PO). Bone ash usually has a density around 3.10 g/mL and a melting point of 1670 °C (3038 °F). Most bones retain their cellular structure through calcination. | 1 | Inorganic Reactions + Inorganic Compounds |
Orthoboric acid was first prepared by Wilhelm Homberg (1652–1715) from borax, by the action of mineral acids, and was given the name ("sedative salt of Homberg"). However boric acid and borates have been used since the time of the ancient Greeks for cleaning, preserving food, and other activities. | 1 | Inorganic Reactions + Inorganic Compounds |
Hydrogen cyanide forms in at least limited amounts from many combinations of hydrogen, carbon, and ammonia. Hydrogen cyanide is produced in large quantities by several processes and is a recovered waste product from the manufacture of acrylonitrile. In 2006, between 500 million and 1 billion pounds (between 230,000 and 450,000 t) were produced in the US.
The most important process is the Andrussow oxidation invented by Leonid Andrussow at IG Farben in which methane and ammonia react in the presence of oxygen at about over a platinum catalyst:
:2 CH + 2 NH + 3 O → 2 HCN + 6 HO
The energy needed for the reaction is provided by the partial oxidation of methane and ammonia.
Of lesser importance is the Degussa process (BMA process) in which no oxygen is added and the energy must be transferred indirectly through the reactor wall:
:CH + NH → HCN + 3H
This reaction is akin to steam reforming, the reaction of methane and water to give carbon monoxide and hydrogen.
In the Shawinigan Process, hydrocarbons, e.g. propane, are reacted with ammonia.
In the laboratory, small amounts of HCN are produced by the addition of acids to cyanide salts of alkali metals:
:H + NaCN → HCN + Na
This reaction is sometimes the basis of accidental poisonings because the acid converts a nonvolatile cyanide salt into the gaseous HCN.
Hydrogen cyanide could be obtained from potassium ferricyanide and acid:
:6 H + [Fe(CN)] → 6 HCN + Fe | 1 | Inorganic Reactions + Inorganic Compounds |
Hydrothermal liquefaction (HTL) is a thermal depolymerization process used to convert wet biomass, and other macromolecules, into crude-like oil under moderate temperature and high pressure. The crude-like oil has high energy density with a lower heating value of 33.8-36.9 MJ/kg and 5-20 wt% oxygen and renewable chemicals. The process has also been called hydrous pyrolysis.
The reaction usually involves homogeneous and/or heterogeneous catalysts to improve the quality of products and yields. Carbon and hydrogen of an organic material, such as biomass, peat or low-ranked coals (lignite) are thermo-chemically converted into hydrophobic compounds with low viscosity and high solubility. Depending on the processing conditions, the fuel can be used as produced for heavy engines, including marine and rail or upgraded to transportation fuels, such as diesel, gasoline or jet-fuels.
The process may be significant in the creation of fossil fuels. Simple heating without water, anhydrous pyrolysis has long been considered to take place naturally during the catagenesis of kerogens to fossil fuels. In recent decades it has been found that water under pressure causes more efficient breakdown of kerogens at lower temperatures than without it. The carbon isotope ratio of natural gas also suggests that hydrogen from water has been added during creation of the gas. | 0 | Organic Reactions |
Two systems exist for the asymmetric hydrogenation of 2-substituted quinolines with isolated yields generally greater than 80% and ee values generally greater than 90%. The first is an iridium(I)/chiral phosphine/I system, first reported by Zhou et al.. While the first chiral phosphine used in this system was MeOBiPhep, newer iterations have focused on improving the performance of this ligand. To this end, systems use phosphines (or related ligands) with improved air stability, recyclability, ease of preparation, lower catalyst loading and the potential role of achiral phosphine additives. As of October 2012 no mechanism appears to have been proposed, although both the necessity of I or a halogen surrogate and the possible role of the heteroaromatic N in assisting reactivity have been documented.
The second is an organocatalytic transfer hydrogenation system based on Hantzsch esters and a chiral Brønsted acid. In this case, the authors envision a mechanism where the isoquinoline is alternately protonated in an activating step, then reduced by conjugate addition of hydride from the Hantzsch ester.
<br />
Much of the asymmetric hydrogenation chemistry of quinoxalines is closely related to that of the structurally similar quinolines. Effective (and efficient) results can be obtained with an Ir(I)/phophinite/I system and a Hantzsh ester-based organocatalytic system, both of which are similar to the systems discussed earlier with regards to quinolines. | 0 | Organic Reactions |
Reductions with diimide are a chemical reactions that convert unsaturated organic compounds to reduced alkane products. In the process, diimide () is oxidized to dinitrogen. | 0 | Organic Reactions |
The primary industrial use of boric acid is in the manufacture of monofilament fiberglass usually referred to as textile fiberglass. Textile fiberglass is used to reinforce plastics in applications that range from boats, to industrial piping to computer circuit boards.
Boric Acid is used as a Nuclear Poison in modern PWR type Nuclear Reactors as it Reduce Fission Process by Reducing Neutrons Flux. It is used in PWR Nuclear Reactor's Coolant water for Controlling Reactor Power as well as to Perform Emergency Reactor Shutdown.
In the jewelry industry, boric acid is often used in combination with denatured alcohol to reduce surface oxidation and thus formation of firescale on metals during annealing and soldering operations.
Boric acid is used in the production of the glass in LCD flat panel displays.
In electroplating, boric acid is used as part of some proprietary formulas. One such known formula calls for about a 1 to 10 ratio of to nickel(II) sulfate|, a very small portion of sodium lauryl sulfate and a small portion of sulfuric acid|.
The solution of orthoboric acid and borax in 4:5 ratio is used as a fire retarding agent of wood by impregnation.
It is also used in the manufacturing of ramming mass, a fine silica-containing powder used for producing induction furnace linings and ceramics.
Boric acid is added to borax for use as welding flux by blacksmiths.
Boric acid, in combination with polyvinyl alcohol (PVA) or silicone oil, is used to manufacture Silly Putty.
Boric acid is also present in the list of chemical additives used for hydraulic fracturing (fracking) in the Marcellus Shale in Pennsylvania. It is often used in conjunction with guar gum as cross-linking and gelling agent for controlling the viscosity and the rheology of the fracking fluid injected at high pressure in the well. It is important to control the fluid viscosity for keeping in suspension on long transport distances the grains of the propping agents aimed at maintaining the cracks in the shales sufficiently open to facilitate the gas extraction after the hydraulic pressure is relieved. The rheological properties of borate cross-linked guar gum hydrogel mainly depend on the pH value.
Boric acid is used in some expulsion-type electrical fuses as a de-ionization/extinguishing agent. During an electrical fault in an expulsion-type fuse, a plasma arc is generated by the disintegration and rapid spring-loaded separation of the fusible element, which is typically a specialized metal rod that passes through a compressed mass of boric acid within the fuse assembly. The high-temperature plasma causes the boric acid to rapidly decompose into water vapor and boric anhydride, and in-turn, the vaporization products de-ionize the plasma, helping to interrupt the electrical fault. | 1 | Inorganic Reactions + Inorganic Compounds |
A mannose sugar is added to the first tryptophan residue in the sequence W–X–X–W (W indicates tryptophan; X is any amino acid). A C-C bond is formed between the first carbon of the alpha-mannose and the second carbon of the tryptophan. However, not all the sequences that have this pattern are mannosylated. It has been established that, in fact, only two thirds are and that there is a clear preference for the second amino acid to be one of the polar ones (Ser, Ala, Gly and Thr) in order for mannosylation to occur. Recently there has been a breakthrough in the technique of predicting whether or not the sequence will have a mannosylation site that provides an accuracy of 93% opposed to the 67% accuracy if we just consider the WXXW motif.
Thrombospondins are one of the proteins most commonly modified in this way. However, there is another group of proteins that undergo C-mannosylation, type I cytokine receptors. C-mannosylation is unusual because the sugar is linked to a carbon rather than a reactive atom such as nitrogen or oxygen. In 2011, the first crystal structure of a protein containing this type of glycosylation was determined—that of human complement component 8. Currently it is established that 18% of human proteins, secreted and transmembrane undergo the process of C-mannosylation. Numerous studies have shown that this process plays an important role in the secretion of Trombospondin type 1 containing proteins which are retained in the endoplasmic reticulum if they do not undergo C-mannosylation This explains why a type of cytokine receptors, erythropoietin receptor remained in the endoplasmic reticulum if it lacked C-mannosylation sites. | 0 | Organic Reactions |
Synthesis of nucleosides involves the coupling of a nucleophilic, heterocyclic base with an electrophilic sugar. The silyl-Hilbert-Johnson (or Vorbrüggen) reaction, which employs silylated heterocyclic bases and electrophilic sugar derivatives in the presence of a Lewis acid, is the most common method for forming nucleosides in this manner. | 0 | Organic Reactions |
Although 1,3-dipolar cycloaddition is a useful method for the generation of five-membered heterocyclic compounds, few methods exist to synthesize five-membered carbocyclic rings in a single step via annulation. Most of these, like TMM cycloaddition, rely on the generation of a suitable three-atom component for combination with a stable two-atom partner such as an alkene or alkyne. When heated, cyclopropene acetals rearrange to vinylcarbenes, which can serve as the three-atom component in cycloadditions with highly electron-deficient alkenes. Zinc homoenolates can also serve as indirect three-atom components, and undergo cyclization to cyclopentenones in the presence of an unsaturated ester. Tandem intermolecular-intramolecular cyclization of homopropargylic radicals leads to methylenecyclopropanes. | 0 | Organic Reactions |
Holmium titanate is an inorganic compound with the chemical formula HoTiO.
Holmium titanate is a spin ice material like dysprosium titanate and holmium stannate. | 1 | Inorganic Reactions + Inorganic Compounds |
Under atmospheric pressure mercuric oxide has two crystalline forms: one is called montroydite (orthorhombic, 2/m 2/m 2/m, Pnma), and the second is analogous to the sulfide mineral cinnabar (hexagonal,
hP6, P3221); both are characterized by Hg-O chains. At pressures above 10 GPa both structures convert to a tetragonal form. | 1 | Inorganic Reactions + Inorganic Compounds |
In the synthesis of the cytotoxic germacranolide sesquiterpene eucannabinolide, Still demonstrates the application of the peripheral attack model to the reduction of a ketone to set a new stereocenter using NaBH. Significantly, the synthesis of eucannabinolide relied on the usage of molecular mechanics (MM2) computational modeling to predict the lowest energy conformation of the macrocycle to design substrate-controlled stereochemical reactions. | 0 | Organic Reactions |
The PROX process allows for the reaction of CO with oxygen, reducing CO concentration from approximately 0.5–1.5% in the feed gas to less than 10 ppm.
:2CO + O → 2CO
Due to the prevalent presence of hydrogen in the feed gas, the competing, undesired combustion of hydrogen will also occur to some degree:
:2H + O → 2HO
The selectivity of the process is a measure of the quality of the reactor, and is defined as the ratio of consumed carbon monoxide to the total of consumed hydrogen and carbon monoxide.
The disadvantage of this technology is its very strong exothermic nature, coupled with a very narrow optimal operation temperature window, and is best operated between 353 and 450 K, yielding a hydrogen loss of around one percent. Effective cooling is therefore required. In order to minimize steam generation, excessive dilution with nitrogen is used. Additionally the reaction is interrupted with an intermediary cooler before proceeding to a second stage.
In the first reaction an excess of oxygen is provided, at around a factor of two, and about 90% of the CO is transformed. In the second step a substantially higher oxygen excess is used, at approximately a factor of 4, which is then processed with the remaining CO, in order to reduce the CO concentration to less than 10 ppm. To also avoid excess CO-fraction loading, the transient operation of a CO adsorber may be important.
The instrumentation and process control complexity requirements are relatively high. The advantage of this technique over selective methanation is the higher space velocity, which reduces the required reactor size. For the case of strong temperature rises, the feed of air can simply be broken.
The technical origins for CO-PROX lies in the synthesis of ammonia (Haber process). Ammonia synthesis also has a strict requirement of CO-free hydrogen, as CO is a strong catalyst poison for the usual catalysts used in this process. | 1 | Inorganic Reactions + Inorganic Compounds |
Radical cyclization reactions produce mono- or polycyclic products through the action of radical intermediates. Because they are intramolecular transformations, they are often very rapid and selective. Selective radical generation can be achieved at carbons bound to a variety of functional groups, and reagents used to effect radical generation are numerous. The radical cyclization step usually involves the attack of a radical on a multiple bond. After this step occurs, the resulting cyclized radicals are quenched through the action of a radical scavenger, a fragmentation process, or an electron-transfer reaction. Five- and six-membered rings are the most common products; formation of smaller and larger rings is rarely observed.
Three conditions must be met for an efficient radical cyclization to take place:
* A method must be available to generate a radical selectively on the substrate.
* Radical cyclization must be faster than trapping of the initially formed radical.
* All steps must be faster than undesired side reactions such as radical recombination or reaction with solvent.
Advantages: because radical intermediates are not charged species, reaction conditions are often mild and functional group tolerance is high and orthogonal to that of many polar processes. Reactions can be carried out in a variety of solvents (including arenes, alcohols, and water), as long as the solvent does not have a weak bond that can undergo abstraction, and products are often synthetically useful compounds that can be carried on using existing functionality or groups introduced during radical trapping.
Disadvantages: the relative rates of the various stages of radical cyclization reactions (and any side reactions) must be carefully controlled so that cyclization and trapping of the cyclized radical is favored. Side reactions are sometimes a problem, and cyclization is especially slow for small and large rings (although macrocyclizations, which resemble intermolecular radical reactions, are often high yielding). | 0 | Organic Reactions |
Ammonium perrhenate is weak oxidizer. It slowly reacts with hydrochloric acid:
:NHReO + 6 HCl → NH[ReClO] + Cl ↑ + 3HO.
It is reduced to metallic Re upon heating under hydrogen:
:2 NHReO + 7 H → 2 Re + 8 HO + 2 NH
Ammonium perrhenate decomposes to volatile ReO starting at 250 °C. When heated in a sealed tube at 500 °C, It decomposes to rhenium dioxide:
:2NHReO → 2ReO + N + 4 HO
The ammonium ion can be displaced with some concentrated nitrates e.g. potassium nitrate,, silver nitrate, etc.:
:NHReO + KNO → KReO ↓ + NHNO
It can be reduced to nonahydridorhenate with sodium in ethanol:
:NHReO + 18Na + 13CHOH → Na[ReH] + 13NaCHO + 3NaOH + NH•HO. | 1 | Inorganic Reactions + Inorganic Compounds |
The hybrid sulfur cycle (HyS) is a two-step water-splitting process intended to be used for hydrogen production. Based on sulfur oxidation and reduction, it is classified as a hybrid thermochemical cycle because it uses an electrochemical (instead of a thermochemical) reaction for one of the two steps. The remaining thermochemical step is shared with the sulfur-iodine cycle.
The Hybrid sulphur cycle (HyS)was initially proposed and developed by Westinghouse Electric Corp. in the 1970s, so it is also known as the "Westinghouse" cycle. Current development efforts in the United States are being led by the Savannah River National Laboratory. | 1 | Inorganic Reactions + Inorganic Compounds |
Unsaturated carbohydrates are desired as they are versatile building blocks that can be used in a variety of reactions. For example, they can be used as intermediates in the synthesis of natural products, or as dienophiles in the Diels-Alder reaction, or as precursors in the synthesis of oligosaccharides. The Tipson–Cohen reaction goes through a syn or anti elimination mechanism to produce an alkene in high to moderate yields. The reaction depends on the neighboring substituents. A mechanism for glucopyranosides and mannooyranosides is shown below.
Scheme 1: Syn elimination occurs with the glucopyranosides. Galactopyranosides follows a similar syn mechanism. Whereas, anti elimination occurs with mannopyranosides. Note that R could be a methanesulfonyl CHOS (Ms), or a toluenesulfonyl CHCHOS (Ts). | 0 | Organic Reactions |
The volatility of the tetrachloride and tetraiodide complexes of Ti(IV) is exploited in the purification of titanium by the Kroll and van Arkel–de Boer processes, respectively.
Metal halides act as Lewis acids. Ferric and aluminium chlorides are catalysts for the Friedel-Crafts reaction, but due to their low cost, they are often added in stoichiometric quantities.
Chloroplatinic acid (HPtCl) is an important catalyst for hydrosilylation. | 1 | Inorganic Reactions + Inorganic Compounds |
Common borate salts include sodium metaborate (NaBO) and borax. Borax is soluble in water, so mineral deposits only occur in places with very low rainfall. Extensive deposits were found in Death Valley and shipped with twenty-mule teams from 1883 to 1889. In 1925, deposits were found at Boron, California on the edge of the Mojave Desert. The Atacama Desert in Chile also contains mineable borate concentrations.
Lithium metaborate, lithium tetraborate, or a mixture of both, can be used in borate fusion sample preparation of various samples for analysis by XRF, AAS, ICP-OES and ICP-MS. Borate fusion and energy dispersive X-ray fluorescence spectrometry with polarized excitation have been used in the analysis of contaminated soils.
Disodium octaborate tetrahydrate (commonly abbreviated DOT) is used as a wood preservative or fungicide. Zinc borate is used as a flame retardant.
Some borates with large anions and multiple cations, like and have been considered for applications in nonlinear optics. | 1 | Inorganic Reactions + Inorganic Compounds |
Pentaoxidane is an inorganic compound of hydrogen and oxygen with the chemical formula . This is one of the most unstable hydrogen polyoxides. | 1 | Inorganic Reactions + Inorganic Compounds |
Fluoroform (CFH) has been employed as a trifluoromethylation reagent for aldehydes in combination with a strong base. | 0 | Organic Reactions |
Homoleptic complexes (complexes with only chloride ligands) are often common reagents. Almost all examples are anions. | 1 | Inorganic Reactions + Inorganic Compounds |
The industrial production of fluorine entails the electrolysis of molten and . The electrolysis of was first used by Henri Moissan in 1886. | 1 | Inorganic Reactions + Inorganic Compounds |
The mechanism of epoxidation with dioxiranes most likely involves concerted oxygen transfer through a spiro transition state. As oxygen transfer occurs, the plane of the oxirane is perpendicular to and bisects the plane of the alkene pi system. The configuration of the alkene is maintained in the product, ruling out long-lived radical intermediates. In addition, the spiro transition state has been used to explain the sense of selectivity in enantioselective epoxidations with chiral ketones.
Diastereoselective epoxidation may be achieved through the use of alkene starting materials with diastereotopic faces. When racemic 3-isopropylcyclohexene was subjected to DMD oxidation, the trans epoxide, which resulted from attack on the less hindered face of the double bond, was the major product. | 0 | Organic Reactions |
There is no limit to the number of possible organic reactions and mechanisms. However, certain general patterns are observed that can be used to describe many common or useful reactions. Each reaction has a stepwise reaction mechanism that explains how it happens, although this detailed description of steps is not always clear from a list of reactants alone. Organic reactions can be organized into several basic types. Some reactions fit into more than one category. For example, some substitution reactions follow an addition-elimination pathway. This overview isn't intended to include every single organic reaction. Rather, it is intended to cover the basic reactions.
In condensation reactions a small molecule, usually water, is split off when two reactants combine in a chemical reaction. The opposite reaction, when water is consumed in a reaction, is called hydrolysis. Many polymerization reactions are derived from organic reactions. They are divided into addition polymerizations and step-growth polymerizations.
In general the stepwise progression of reaction mechanisms can be represented using arrow pushing techniques in which curved arrows are used to track the movement of electrons as starting materials transition to intermediates and products. | 0 | Organic Reactions |
Modern high-pressure thermal cracking operates at absolute pressures of about 7,000 kPa. An overall process of disproportionation can be observed, where "light", hydrogen-rich products are formed at the expense of heavier molecules which condense and are depleted of hydrogen. The actual reaction is known as homolytic fission and produces alkenes, which are the basis for the economically important production of polymers.
Thermal cracking is currently used to "upgrade" very heavy fractions or to produce light fractions or distillates, burner fuel and/or petroleum coke. Two extremes of the thermal cracking in terms of the product range are represented by the high-temperature process called "steam cracking" or pyrolysis (ca. 750 °C to 900 °C or higher) which produces valuable ethylene and other feedstocks for the petrochemical industry, and the milder-temperature delayed coking (ca. 500 °C) which can produce, under the right conditions, valuable needle coke, a highly crystalline petroleum coke used in the production of electrodes for the steel and aluminium industries.
William Merriam Burton developed one of the earliest thermal cracking processes in 1912 which operated at and an absolute pressure of and was known as the Burton process. Shortly thereafter, in 1921, C.P. Dubbs, an employee of the Universal Oil Products Company, developed a somewhat more advanced thermal cracking process which operated at and was known as the Dubbs process. The Dubbs process was used extensively by many refineries until the early 1940s when catalytic cracking came into use. | 0 | Organic Reactions |
After decades of research, EMPA researchers and others are experimenting with concentrated sodium hydroxide (NaOH) as the thermal storage or seasonal reservoir medium for power plants and domestic space-heating. If water is added to solid or concentrated sodium hydroxide (NaOH), heat is released. The dilution is exothermic – chemical energy is released in the form of heat. Conversely, by applying heat energy into a dilute sodium hydroxide solution the water will evaporate so that the solution becomes more concentrated and thus stores the supplied heat as latent chemical energy. | 1 | Inorganic Reactions + Inorganic Compounds |
The main borate anions are:
* tetrahydroxyborate , found in sodium tetrahydroxyborate .
* orthoborate , found in trisodium orthoborate
* , found in the calcium yttrium borosilicate oxyapatite
* perborate , as in sodium perborate
* metaborate or its cyclic trimer , found in sodium metaborate
* diborate , found in magnesium diborate (suanite),
* triborate , found in calcium aluminium triborate (johachidolite),
* tetraborate , found in anhydrous borax
* tetrahydroxytetraborate , found in borax "decahydrate"
* tetraborate(6-) found in lithium tetraborate(6-)
* pentaborate or , found in sodium pentaborate
* octaborate found in disodium octaborate | 1 | Inorganic Reactions + Inorganic Compounds |
Calcium hydroxide is commonly used to prepare lime mortar.
One significant application of calcium hydroxide is as a flocculant, in water and sewage treatment. It forms a fluffy charged solid that aids in the removal of smaller particles from water, resulting in a clearer product. This application is enabled by the low cost and low toxicity of calcium hydroxide. It is also used in fresh-water treatment for raising the pH of the water so that pipes will not corrode where the base water is acidic, because it is self-regulating and does not raise the pH too much.
It is also used in the preparation of ammonia gas (NH), using the following reaction:
: Ca(OH) + 2 NHCl → 2 NH + CaCl + 2 HO
Another large application is in the paper industry, where it is an intermediate in the reaction in the production of sodium hydroxide. This conversion is part of the causticizing step in the Kraft process for making pulp. In the causticizing operation, burned lime is added to green liquor, which is a solution primarily of sodium carbonate and sodium sulfate produced by dissolving smelt, which is the molten form of these chemicals from the recovery furnace.
In orchard crops, calcium hydroxide is used as a fungicide. Applications of lime water prevent the development of cankers caused by the fungal pathogen Neonectria galligena. The trees are sprayed when they are dormant in winter to prevent toxic burns from the highly reactive calcium hydroxide. This use is authorised in the European Union and the United Kingdom under Basic Substance regulations.
Calcium hydroxide is used in dentistry, primarily in the specialty of endodontics. | 1 | Inorganic Reactions + Inorganic Compounds |
was first prepared in 1835 by M. Gregory by the reaction of disulfur dichloride with ammonia, a process that has been optimized:
Coproducts of this reaction include heptasulfur imide () and elemental sulfur. A related synthesis employs instead:
An alternative synthesis entails the use of as a precursor with pre-formed S–N bonds. is prepared by the reaction of lithium bis(trimethylsilyl)amide and sulfur dichloride|.
The reacts with the combination of and sulfuryl chloride| to form , trimethylsilyl chloride, and sulfur dioxide: | 1 | Inorganic Reactions + Inorganic Compounds |
Several commodity chemicals are produced by alkylation. Included are several fundamental benzene-based feedstocks such as ethylbenzene (precursor to styrene), cumene (precursor to phenol and acetone), linear alkylbenzene sulfonates (for detergents). | 0 | Organic Reactions |
The reaction mechanism was first investigated by Scott Searles and coworkers at the University of Missouri. Overall, the reaction can be thought of as a reductive coupling of the carbonyl compound and the terminal alkyne. In the Crabbé reaction, the secondary amine serves as the hydride donor, which results in the formation of the corresponding imine as the byproduct. Thus, remarkably, the secondary amine serves as Brønsted base, ligand for the metal ion, iminium-forming carbonyl activator, and the aforementioned two-electron reductant in the same reaction.
In broad strokes, the mechanism of the reaction is believed to first involve a Mannich-like addition of the species into the iminium ion formed by condensation of the aldehyde and the secondary amine. This first part of the process is a so-called A coupling reaction (A stands for aldehyde-alkyne-amine). In the second part, the α-amino alkyne then undergoes a formal retro-imino-ene reaction, an internal redox process, to deliver the desired allene and an imine as the oxidized byproduct of the secondary amine. These overall steps are supported by deuterium labeling and kinetic isotope effect studies. Density functional theory computations were performed to better understand the second part of the reaction. These computations indicate that the uncatalyzed process (either a concerted but highly asynchronous process or a stepwise process with a fleeting intermediate) involves a prohibitively high-energy barrier. The metal-catalyzed reaction, on the other hand, is energetically reasonable and probably occurs via a stepwise hydride transfer to the alkyne followed by C–N bond scission in a process similar to those proposed for formal [3,3]-sigmatropic rearrangements and hydride transfer reactions catalyzed by gold(I) complexes. A generic mechanism showing the main features of the reaction (under Crabbé's original conditions) is given below:(The copper catalyst is shown simply as "CuBr" or "Cu", omitting any additional amine or halide ligands or the possibility of dinuclear interactions with other copper atoms. Condensation of formaldehyde and diisopropylamine to form the iminium ion and steps involving complexation and decomplexation of Cu are also omitted here for brevity.)
Since 2012, Ma has reported several catalytic enantioselective versions of the Crabbé reaction in which chiral PINAP (aza-BINAP) based ligands for copper are employed. The stepwise application of copper and zinc catalysis was required: the copper promotes the Mannich-type condensation, while subsequent one-step addition of zinc iodide catalyzes the imino-retro-ene reaction. | 0 | Organic Reactions |
Macrocyclic rings containing sp centers display a conformational preference for the sp centers to avoid transannular nonbonded interactions by orienting perpendicular to the plan of the ring. Clark W. Still proposed that the ground state conformations of macrocyclic rings, containing the energy minimized orientation of the sp center, display one face of an olefin outwards from the ring. Addition of reagents from the outside the olefin face and the ring (peripheral attack) is thus favored, while attack from across the ring on the inward diastereoface is disfavored. Ground state conformations dictate the exposed face of the reactive site of the macrocycle, thus both local and distant stereocontrol elements must be considered. The peripheral attack model holds well for several classes of macrocycles, though relies on the assumption that ground state geometries remain unperturbed in the corresponding transition state of the reaction. | 0 | Organic Reactions |
The use of zinc chloride as a flux, sometimes in a mixture with ammonium chloride (see also Zinc ammonium chloride), involves the production of HCl and its subsequent reaction with surface oxides.
Zinc chloride reacts with metal oxides (MO) to give derivatives of the idealized formula . This reaction is relevant to the utility of solution as a flux for soldering — it dissolves passivating oxides, exposing the clean metal surface. Fluxes with as an active ingredient are sometimes called "tinner's fluid".
Zinc chloride forms two salts with ammonium chloride: and , which decompose on heating liberating HCl, just as zinc chloride hydrate does. The action of zinc chloride/ammonium chloride fluxes, for example, in the hot-dip galvanizing process produces gas and ammonia fumes. | 1 | Inorganic Reactions + Inorganic Compounds |
A solution of sulfur tetrafluoride in hydrogen fluoride converts hydroxy-containing amino acids to the fluoro amino acids:
When vicinal diols are combined with SF, difluorination occurs with inversion of configuration at only one of the alcohols. This was demonstrated in the synthesis of meso-difluorosuccinate from (L)-tartrate and the synthesis of (D)- and (L)-difluorosuccinate from meso-tartrate.
Carbonyl compounds generally react with SF to yield geminal difluorides. Reaction times tend to be on the order of hours and yields are moderate. Fluorination of lactones can provide heterocyclic fluorides, although ring opening has been observed for γ-butyrolactone. The six-membered lactide does not experience ring opening.
Fluorination opens epoxides to give either geminal or vicinal difluorides in most cases. Monoarylepoxides give geminal products with migration of the aryl group. Yields are low for sterically hindered di- and trisubstituted epoxides. Epoxides substituted with an ester group give vicinal difluorides via an alkoxysulfur trifluoride intermediate.
Carboxylic acids react with SF to afford trifluoromethyl compounds:
The formation of the trifluoromethyl derivative sometimes competes with formation of tetrafluoroalkyl ethers, which arise from the reaction between difluoromethyl cation and acyl fluoride.
Sulfur tetrafluoride can be used to fluorinate polymers efficiently. This often has a profound effect on polymer properties—fluorination of polyvinyl alcohol, for instance, improves its resistance to strong acids and bases.
A prostaglandin bearing a trifluoromethyl group at C-16 is prepared using sulfur tetrafluoride. | 0 | Organic Reactions |
Alkyne activation with π–acidic metals such as Au or Pt is a conventional method in complex organic manifold synthesis, however how this activation exacts reactivity is not fully understood and thus mechanism is largely proposed on the basis of reaction outcome and theoretical calculations. Cationic Au(I) and Pt(II) catalyst are attractive choices as they display strong Lewis acid character and the ability to stabilize cationic intermediates while being bench stable.
A versatile function of Au(I) catalyzed enyne cycloisomerization is the construction of asymmetric medium–sized rings, which is a challenge in the synthesis of ornamented molecular design. Convenient access to asymmetric 7– and 8–membered carbocycles is possible using chiral BINAP Au(I) gold catalyst, giving a wide variety of products.
It is proposed that intramolecular cyclopropanation occurs via a 1,2–shift of the propargyl ester mediated by Au to give a syn–Au vinyl carbenoid species (29). Computational studies show that the syn–intermediate, 29, is formed under kinetic control and it is suggested that it is in equilibrium with the thermodynamically favorable cis–intermediate which may be intercepted by a nucleophile leading to vinyl cyclopropane diene products, however this is beyond the scope of this article.
Vinylcycloalkenes is another functional class of products accessible through alkyne activation of enynes with π–acidic metals. PtCl has been shown to catalyze the formation of a variety of exotic vinylcycloalkenes from readily accessible starting materials (figure 10).
Notably, a ring expansion is observed for enynes with cyclic alkene motifs. This is rationalized by a formal insertion of the methylene group of the olefin between the two carbons of the alkyne; a mechanistic reasoning for this ring expansion has also been proposed. The formation of these vinycloalkenes in concert with its ability to undergo a ring expansion was exploited to construct intermediate 36 en route to streptorubin B. A similar transformation is possible using cationic Au(I) complexes, however here one can select for vinycycloalkene products through a mechanism proceeding via an initial 5–exo–dig or bicyclopropanes can be produced via an initial 6–endo–dig. It is suggested through DFT calculations that the 5–exo–dig cyclization is favored for Au(I) complexes as it has a lower activation barrier relative to the 6–endo–dig and indeed numerous examples of vinylcycloalkenes products produced via an initial 5–exo–dig are given (figure 11).
The reactivity can be reversed by careful selection of reaction conditions, catalyst selection and substrate. The divergent reactivity of these transition metal catalyzed cycloisomerizations further demonstrates their synthetic utility in building unique molecular skeletons. | 0 | Organic Reactions |
C-alkylation is a process for the formation of carbon-carbon bonds. The largest example of this takes place in the alkylation units of petrochemical plants, which convert low-molecular-weight alkenes into high octane gasoline components. Electron-rich species such as phenols are also commonly alkylated to produce a variety of products; examples include linear alkylbenzenes used in the production of surfactants like LAS, or butylated phenols like BHT, which are used as antioxidants. This can be achieved using either acid catalysts like Amberlyst, or Lewis acids like aluminium. On a laboratory scale the Friedel–Crafts reaction uses alkyl halides, as these are often easier to handle than their corresponding alkenes, which tend to be gasses. The reaction is catalysed by aluminium trichloride. This approach is rarely used industrially as alkyl halides are more expensive than alkenes. | 0 | Organic Reactions |
Radical cyclization reactions are organic chemical transformations that yield cyclic products through radical intermediates. They usually proceed in three basic steps: selective radical generation, radical cyclization, and conversion of the cyclized radical to product. | 0 | Organic Reactions |
In an alkene ring that does not contain an oxygen atom, any large substituent prefers to be in an equatorial position, in order to minimize steric effects. It has been observed in rings containing oxocarbenium ions that electronegative substituents prefer the axial or pseudo-axial positions. When the electronegative atom is in the axial position, its electron density can be donated through space to the positively charged oxygen atom in the ring. This electronic interaction stabilizes the axial conformation. Hydroxyl groups, ethers and halogens are examples of substituents that exhibit this phenomenon. Stereoelectronic effects must be taken into consideration when determining the lowest energy conformation in the analysis for nucleophilic addition to an oxocarbenium ion. | 0 | Organic Reactions |
In addition to the use of strong bases, enolates can be generated using a Lewis acid and a weak base ("soft conditions"):
For deprotonation to occur, the stereoelectronic requirement is that the alpha-C-H sigma bond must be able to overlap with the pi* orbital of the carbonyl: | 0 | Organic Reactions |
Gallium arsenide is an important semiconductor material for high-cost, high-efficiency solar cells and is used for single-crystalline thin-film solar cells and for multi-junction solar cells.
The first known operational use of GaAs solar cells in space was for the Venera 3 mission, launched in 1965. The GaAs solar cells, manufactured by Kvant, were chosen because of their higher performance in high temperature environments. GaAs cells were then used for the Lunokhod rovers for the same reason.
In 1970, the GaAs heterostructure solar cells were developed by the team led by Zhores Alferov in the USSR, achieving much higher efficiencies. In the early 1980s, the efficiency of the best GaAs solar cells surpassed that of conventional, crystalline silicon-based solar cells. In the 1990s, GaAs solar cells took over from silicon as the cell type most commonly used for photovoltaic arrays for satellite applications. Later, dual- and triple-junction solar cells based on GaAs with germanium and indium gallium phosphide layers were developed as the basis of a triple-junction solar cell, which held a record efficiency of over 32% and can operate also with light as concentrated as 2,000 suns. This kind of solar cell powered the Mars Exploration Rovers Spirit and Opportunity, which explored Mars' surface. Also many solar cars utilize GaAs in solar arrays, as did the Hubble Telescope.
GaAs-based devices hold the world record for the highest-efficiency single-junction solar cell at 29.1% (as of 2019). This high efficiency is attributed to the extreme high quality GaAs epitaxial growth, surface passivation by the AlGaAs, and the promotion of photon recycling by the thin film design. GaAs-based photovoltaics are also responsible for the highest efficiency (as of 2022) of conversion of light to electricity, as researchers from the Fraunhofer Institute for Solar Energy Systems achieved a 68.9% efficiency when exposing a GaAs thin film photovoltaic cell to monochromatic laser light with a wavelength of 858 nanometers.
Today, multi-junction GaAs cells have the highest efficiencies of existing photovoltaic cells and trajectories show that this is likely to continue to be the case for the foreseeable future. In 2022, Rocket Lab unveiled a solar cell with 33.3% efficiency based on inverted metamorphic multi-junction (IMM) technology. In IMM, the lattice-matched (same lattice parameters) materials are grown first, followed by mismatched materials. The top cell, GaInP, is grown first and lattice matched to the GaAs substrate, followed by a layer of either GaAs or GaInAs with a minimal mismatch, and the last layer has the greatest lattice mismatch. After growth, the cell is mounted to a secondary handle and the GaAs substrate is removed. A main advantage of the IMM process is that the inverted growth according to lattice mismatch allows a path to higher cell efficiency.
Complex designs of AlGaAs-GaAs devices using quantum wells can be sensitive to infrared radiation (QWIP).
GaAs diodes can be used for the detection of X-rays. | 1 | Inorganic Reactions + Inorganic Compounds |
Lanthanum(III) iodide can be synthesised by the reaction of lanthanum metal with mercury(II) iodide:
:2 La + 3 HgI → 2 LaI + 3 Hg
It can also be prepared from the elements, that is by the reaction of metallic lanthanum with iodine:
:2 La + 3 I → 2 LaI
While lanthanum(III) iodide solutions can be generated by dissolving lanthanum oxide in hydroiodic acid, the product will hydrolyse and form polymeric hydroxy species:
:LaO + 6 HI → 2 LaI + 3 HO → further reactions | 1 | Inorganic Reactions + Inorganic Compounds |
Sodium iodide is used for conversion of alkyl chlorides into alkyl iodides. This method, the Finkelstein reaction, relies on the insolubility of sodium chloride in acetone to drive the reaction:
::R–Cl + NaI → R–I + NaCl | 1 | Inorganic Reactions + Inorganic Compounds |
The electronic structures of Fe(SCNMe)(NE), where E=O, S, or Se were calculated using Density Functional Theory methods. It was found that the large Mulliken spin density remained concentrated on the Fe(NE) core and Fe-N distances experienced little change from the chalcogen atom used. The HOMO of both nitrosyl and thionitrosyl complexes retained 1a (d) character. The small changes in the energies of the spin orbitals of the complexes, particularly the decreased energetic gap between 2b and 1b and 2b and 1b orbitals is attributed to NS being a weaker π-acceptor than NO. | 1 | Inorganic Reactions + Inorganic Compounds |
Because the substituents attached to the imine nitrogen exert a profound influence on reactivity, few general catalyst systems exist for the enantioselective hydrogenation of imines and imine derivatives. However, catalyst systems have been developed that catalyze hydrogenation of particular classes of imines with high enantioselectivity and yield. This section describes some of these systems and is organized by the substitution pattern of the imine.
α-Carboxy imines are attractive precursors for α-amino acids. Organocatalytic reduction of these substrates is possible using a Hantzsch ester and a chiral phosphoric acid catalyst. | 0 | Organic Reactions |
Aminosulfuranes compare favorably with many of the other fluorination methods available. They are easier to handle than sulfur tetrafluoride; however SF does not promote cationic rearrangements. With respect to carboxylic acids, aminosulfuranes and SF are complementary: the former gives acid fluorides, while the latter gives trifluoromethyl compounds.
Perfluorinated alkylamines, such as Ishikawas reagent (N,N'-diethyl-1,1,2,3,3,3-hexafluoropropylamine WRONG MOLECULE IN SCHEME BELOW), are highly selective for hydroxyl groups and do not react with aldehydes and ketones. The amide byproducts of these reagents, however, are harder to separate from the desired products than aminosulfurane byproducts.
Alkali and tetraalkylammonium fluorides can be used to displace sulfonate esters; however, these reactions require higher temperatures than aminosulfurane fluorination of the corresponding free alcohols. | 0 | Organic Reactions |
Ammonia is explosive when mixed with air (15 – 25%). Other lower azanes can also form explosive mixtures with air. The lighter liquid azanes are highly flammable; this risk increases with the length of the nitrogen chain. One consideration for detection and risk control is that ammonia is lighter than air, creating the possibility of accumulation on ceilings. | 1 | Inorganic Reactions + Inorganic Compounds |
Oxidation with dioxiranes refers to the introduction of oxygen into organic molecules through the action of a dioxirane. Dioxiranes are well known for their oxidation of alkenes to epoxides; however, they are also able to oxidize other unsaturated functionality, heteroatoms, and alkane C-H bonds. | 0 | Organic Reactions |
The von Braun reaction is an organic reaction in which a tertiary amine reacts with cyanogen bromide to an organocyanamide.
An example is the reaction of N,N-dimethyl-1-naphthylamine:
These days, most chemist have replaced cyanogen bromide reagent with chloroethyl chloroformate reagent instead. It appears as though Olofson et al. was the first chemist to have reported this. | 0 | Organic Reactions |
At low temperatures, has an A- hexagonal crystal structure. The metal atoms are surrounded by a 7 coordinate group of atoms, the oxygen ions are in an octahedral shape around the metal atom and there is one oxygen ion above one of the octahedral faces. On the other hand, at high temperatures lanthanum oxide converts to a C- cubic crystal structure. The ion is surrounded by six ions in a hexagonal configuration. | 1 | Inorganic Reactions + Inorganic Compounds |
Zinc chloride dissolves readily in water to give species and some free chloride. Aqueous solutions of are acidic: a 6 M aqueous solution has a pH of 1. The acidity of aqueous solutions relative to solutions of other Zn salts (say the sulfate) is due to the formation of the tetrahedral chloro aqua complexes where the reduction in coordination number from 6 to 4 further reduces the strength of the O–H bonds in the solvated water molecules.
In alkali solution, zinc chloride converts to various zinc hydroxychlorides. These include , , , and the insoluble . The latter is the mineral simonkolleite. When zinc chloride hydrates are heated, HCl gas evolves and hydroxychlorides result.
When solutions of zinc chloride are treated with ammonia, various ammine complexes are produced. These include and on concentration . The former contains the ion, and the latter is molecular with a distorted tetrahedral geometry. The species in aqueous solution have been investigated and show that is the main species present with also present at lower :Zn ratio. | 1 | Inorganic Reactions + Inorganic Compounds |
The Tishchenko reaction is an organic chemical reaction that involves disproportionation of an aldehyde in the presence of an alkoxide. The reaction is named after Russian organic chemist Vyacheslav Tishchenko, who discovered that aluminium alkoxides are effective catalysts for the reaction.
In the related Cannizzaro reaction, the base is sodium hydroxide and then the oxidation product is a carboxylic acid and the reduction product is an alcohol. | 0 | Organic Reactions |
To a cold (–78°) stirred solution of lithium diisopropylamide (1.4–1.5 mmol/mmol of ketone) in dry THF (4 mL/mmol of base) under an atmosphere of argon was added slowly a solution of n-butyl-trans-2-vinylcyclopropyl ketone (1.19 mmol) in dry THF (1 mL/mmol of ketone), and the resulting solution was stirred at –78° for 45 minutes. A solution of freshly sublimed tert-butyldimethylsilyl chloride (1.6 mmol/mmol of ketone) in dry THF (1 mL/mmol of chloride) was added, followed by dry HMPA (0.5 mL/mmol of ketone). The solution was stirred at –78° for 15 minutes and at room temperature for 2–3 hours, and then it was partitioned between saturated aqueous sodium bicarbonate and pentane (10 mL and 20 mL/mmol of ketone, respectively). The aqueous phase was washed twice with pentane. The combined extract was washed four times with saturated aqueous sodium bicarbonate and twice with brine, and then dried (MgSO). Removal of the solvent, followed by bulb-to-bulb distillation of the remaining oil, gave the corresponding silyl enol ether as a colorless oil that exhibited no IR carbonyl stretching absorption. Thermolysis of the silyl enol ether was accomplished by heating (neat, argon atmosphere) at 230° (air-bath temperature) for 30–60 minutes. Direct distillation (140–150°/12 torr) of the resultant materials provided the cycloheptadiene in 85% yield: IR (film) 1660, 1260, 840 cm–1; 1H NMR (CDCl) δ 0.09 (s, 6H), 0.88 (s, 9H), 0.7–2.75 (m, 14H), 4.8 (t, 1H, J = 5.5 Hz), 5.5–5.9 (m, 2H). | 0 | Organic Reactions |
In 1970-75, Giguère et al. observed infrared and Raman spectra of dilute aqueous solutions of trioxidane. In 2005, trioxidane was observed experimentally by microwave spectroscopy in a supersonic jet. The molecule exists in a skewed structure, with an oxygen–oxygen–oxygen–hydrogen dihedral angle of 81.8°. The oxygen–oxygen bond lengths of 142.8 picometer are slightly shorter than the 146.4 pm oxygen–oxygen bonds in hydrogen peroxide. Various dimeric and trimeric forms also seem to exist.
There is a trend of increasing gas-phase acidity and corresponding pK as the number of oxygen atoms in the chain increases in HOH structures (n=1,2,3). | 1 | Inorganic Reactions + Inorganic Compounds |
Elaidinization is any chemical reaction which convert a cis- olefin to a trans- olefin in unsaturated fatty acids. This is often performed on fats and oils to increase both the melting point and the shelf life without reducing the degree of unsaturation. The term originates from elaidic acid, the trans-isomer of oleic acid. | 0 | Organic Reactions |
Boric acid is used in some nuclear power plants as a neutron poison. The boron in boric acid reduces the probability of thermal fission by absorbing some thermal neutrons. Fission chain reactions are generally driven by the probability that free neutrons will result in fission and is determined by the material and geometric properties of the reactor. Natural boron consists of approximately 20% boron-10 and 80% boron-11 isotopes. Boron-10 has a high cross-section for absorption of low energy (thermal) neutrons. By increasing boric acid concentration in the reactor coolant, the probability that a neutron will cause fission is reduced. Changes in boric acid concentration can effectively regulate the rate of fission taking place in the reactor. During normal at power operation, boric acid is used only in pressurized water reactors (PWRs), whereas boiling water reactors (BWRs) employ control rod pattern and coolant flow for power control, although BWRs can use an aqueous solution of boric acid and borax or sodium pentaborate for an emergency shutdown system if the control rods fail to insert. Boric acid may be dissolved in spent fuel pools used to store spent fuel elements. The concentration is high enough to keep neutron multiplication at a minimum. Boric acid was dumped over Reactor 4 of the Chernobyl nuclear power plant after its meltdown to prevent another reaction from occurring. | 1 | Inorganic Reactions + Inorganic Compounds |
Lanthanum oxide can crystallize in at least three polymorphs.
Hexagonal has been produced by spray pyrolysis of lanthanum chloride.
An alternative route to obtaining hexagonal involves precipitation of nominal from aqueous solution using a combination of 2.5% and the surfactant sodium dodecyl sulfate followed by heating and stirring for 24 hours at 80 °C:
Other routes include: | 1 | Inorganic Reactions + Inorganic Compounds |
* The Tishchenko reaction of acetaldehyde gives the commercially important solvent ethyl acetate. The reaction is catalyzed by aluminium alkoxides.
* The Tishchenko reaction is used to obtain isobutyl isobutyrate, a specialty solvent.
* Hydroxypivalic acid neopentyl glycol ester is produced by a Tishchenko reaction from hydroxypivaldehyde in the presence of a basic catalyst (e.g., aluminium oxide).
* The Tishchenko reaction of paraformaldehyde in the presence of aluminum methylate or magnesium methylate forms methyl formate.
* Paraformaldehyde reacts with boric acid to form methyl formate. The key step in the reaction mechanism for this reaction is a 1,3-hydride shift in the hemiacetal intermediate formed from two successive nucleophilic addition reactions, the first one from the catalyst. The hydride shift regenerates the alkoxide catalyst. | 0 | Organic Reactions |
Xenon dioxide, or xenon(IV) oxide, is a compound of xenon and oxygen with formula XeO which was synthesized in 2011. It is synthesized at 0 °C by hydrolysis of xenon tetrafluoride in aqueous sulfuric acid: | 1 | Inorganic Reactions + Inorganic Compounds |
Ester pyrolysis in organic chemistry is a vacuum pyrolysis reaction converting esters containing a β-hydrogen atom into the corresponding carboxylic acid and the alkene. The reaction is an E elimination and operates in a syn fashion.
Examples include the synthesis of acrylic acid from ethyl acrylate at 590 °C, the synthesis of 1,4-pentadiene from 1,5-pentanediol diacetate at 575 °C or the construction of a cyclobutene framework at 700 °C | 0 | Organic Reactions |
Thus, although many zinc salts have different formulas and different crystal structures, these salts behave very similarly in aqueous solution. For example, solutions prepared from any of the polymorphs of , as well as other halides (bromide, iodide), and the sulfate can often be used interchangeably for the preparation of other zinc compounds. Illustrative is the preparation of zinc carbonate: | 1 | Inorganic Reactions + Inorganic Compounds |
Cobalt chloride is a common visual moisture indicator due to its distinct colour change when hydrated. The colour change is from some shade of blue when dry, to a pink when hydrated, although the shade of colour depends on the substrate and concentration. It is impregnated into paper to make test strips for detecting moisture in solutions, or more slowly, in air/gas. Desiccants such as silica gel can incorporate cobalt chloride to indicate when it is "spent" (i.e. hydrated). | 1 | Inorganic Reactions + Inorganic Compounds |
Sodium iodide, as well as potassium iodide, is commonly used to treat and prevent iodine deficiency. Iodized table salt contains 10 ppm iodide. | 1 | Inorganic Reactions + Inorganic Compounds |
In stereochemistry, macrocyclic stereocontrol refers to the directed outcome of a given intermolecular or intramolecular chemical reaction that is governed by the conformational preference of a macrocycle (a molecule containing a ring of 8 or more atoms). | 0 | Organic Reactions |
GaAs can be used for various transistor types:
* Metal–semiconductor field-effect transistor (MESFET)
* High-electron-mobility transistor (HEMT)
* Junction field-effect transistor (JFET)
* Heterojunction bipolar transistor (HBT)
* Metal–oxide–semiconductor field-effect transistor (MOSFET)
The HBT can be used in integrated injection logic (IL).
The earliest GaAs logic gate used Buffered FET Logic (BFL).
From to 1995 the main logic families used were:
* Source-coupled FET logic (SCFL) fastest and most complex, (used by TriQuint & Vitesse)
* Capacitor–diode FET logic (CDFL) (used by Cray for Cray-3)
* Direct-coupled FET logic (DCFL) simplest and lowest power (used by Vitesse for VLSI gate arrays) | 1 | Inorganic Reactions + Inorganic Compounds |
Praseodymium(III) fluoride forms pale green crystals of trigonal system (or hexagonal system), space group P 3c1, (or P 6/mcm), cell parameters a = 0.7078 nm, c = 0.7239 nm, Z = 6, structure like cerium(III) fluoride (CeF). | 1 | Inorganic Reactions + Inorganic Compounds |
Plutonium selenide forms black crystals of a cubic system, space group Fmm, cell parameters a = 0.57934 nm, Z = 4, structure of the NaCl type.
With increasing pressure, two phase transitions occur: at 20 GPa into the trigonal system and at 35 GPa into the cubic system, a structure of the CsCl type.
Its magnetic susceptibility follows the Curie-Weiss law. | 1 | Inorganic Reactions + Inorganic Compounds |
A coarctate reaction is a concerted reaction whose transition state involves two rings, in which at least one atom undergoes the simultaneous making and breaking of two bonds. It is an uncommon reaction topology, compared with linear topology and pericyclic topology (itself subdivided into Hückel and Möbius topologies). The name is derived from the Latin , meaning . | 0 | Organic Reactions |
* Mercury(I) chloride disproportionates upon UV-irradiation:
* Phosphorous acid disproportionates upon heating to 200°C to give phosphoric acid and phosphine:
* Desymmetrizing reactions are sometimes referred to as disproportionation, as illustrated by the thermal degradation of bicarbonate:
:: The oxidation numbers remain constant in this acid-base reaction.
* Another variant on disproportionation is radical disproportionation, in which two radicals form an alkene and an alkane.
* Disproportionation of sulfur intermediates by microorganisms are widely observed in sediments.
* Chlorine gas reacts with dilute sodium hydroxide to form sodium chloride, sodium chlorate and water. The ionic equation for this reaction is as follows:
:: The chlorine reactant is in oxidation state 0. In the products, the chlorine in the Cl ion has an oxidation number of −1, having been reduced, whereas the oxidation number of the chlorine in the ClO ion is +5, indicating that it has been oxidized.
* Decomposition of numerous interhalogen compounds involve disproportionation. Bromine fluoride undergoes disproportionation reaction to form bromine trifluoride and bromine in non-aqueous media:
* The dismutation of superoxide free radical to hydrogen peroxide and oxygen, catalysed in living systems by the enzyme superoxide dismutase:
:: The oxidation state of oxygen is −1/2 in the superoxide free radical anion, −1 in hydrogen peroxide and 0 in dioxygen.
* In the Cannizzaro reaction, an aldehyde is converted into an alcohol and a carboxylic acid. In the related Tishchenko reaction, the organic redox reaction product is the corresponding ester. In the Kornblum–DeLaMare rearrangement, a peroxide is converted to a ketone and an alcohol.
* The disproportionation of hydrogen peroxide into water and oxygen catalysed by either potassium iodide or the enzyme catalase:
* In the Boudouard reaction, carbon monoxide disproportionates to carbon and carbon dioxide. The reaction is for example used in the HiPco method for producing carbon nanotubes, high-pressure carbon monoxide disproportionates when catalysed on the surface of an iron particle:
* Nitrogen has oxidation state +4 in nitrogen dioxide, but when this compound reacts with water, it forms both nitric acid and nitrous acid, where nitrogen has oxidation states +5 and +3 respectively:
* Dithionite undergoes acid hydrolysis to thiosulfate and bisulfite:
* Dithionite also undergoes alkaline hydrolysis to sulfite and sulfide:
* Dithionate is prepared on a larger scale by oxidizing a cooled aqueous solution of sulfur dioxide with manganese dioxide: | 0 | Organic Reactions |
There are different enzymes to remove the glycans from the proteins or remove some part of the sugar chain.
* α2-3,6,8,9-Neuraminidase (from Arthrobacter ureafaciens): cleaves all non-reducing terminal branched and unbranched sialic acids.
* β1,4-Galactosidase (from Streptococcus pneumoniae): releases only β1,4-linked, nonreducing terminal galactose from complex carbohydrates and glycoproteins.
* β-N-Acetylglucosaminidase (from Streptococcus pneumoniae): cleaves all non-reducing terminal β-linked N-acetylglucosamine residues from complex carbohydrates and glycoproteins.
* endo-α-N-Acetylgalactosaminidase (O-glycosidase from Streptococcus pneumoniae): removes O-glycosylation. This enzyme cleaves serine- or threonine-linked unsubstituted Galβ1,3GalNAc
* PNGase F: cleaves asparagine-linked oligosaccharides unless α1,3-core fucosylated. | 0 | Organic Reactions |
Cadmium sulfide can be dissolved in acids.
:CdS + 2 HCl → CdCl + HS
When solutions of sulfide containing dispersed CdS particles are irradiated with light, hydrogen gas is generated:
: HS → H + S ΔH = +9.4 kcal/mol
The proposed mechanism involves the electron/hole pairs created when incident light is absorbed by the cadmium sulfide followed by these reacting with water and sulfide:
:Production of an electron–hole pair
::CdS + hν → e + h
:Reaction of electron
::2e + 2HO → H + 2OH
:Reaction of hole
::2h + S → S | 1 | Inorganic Reactions + Inorganic Compounds |
At high pressure, zirconium tungstate undergoes a series of phase transitions, first to an amorphous phase, and then to a UO-type phase, in which the zirconium and tungsten atoms are disordered. | 1 | Inorganic Reactions + Inorganic Compounds |
In 2006 Goossen et al. proposed a reaction to synthesize biaryl compounds via catalytic decarboxylative cross coupling.
The mechanism involves two overlapping cycles, one using a copper halide and the other using palladium. The decarboxylation step occurs between the substituted benzoic acid and copper halide to form the intermediate aryl copper species. The palladium initially undergoes oxidative addition from the aryl halide to form a Pd(II) aryl complex. After both of these initial steps, the substituted aryl copper undergoes trans-metalation with the palladium complex. This step forms the copper halide, which then undergoes anion exchange with the substituted benzoic acid to reform the aryl copper intermediate, continuing the catalytic cycle. The other complex formed in the trans-metalation step is a bis-aryl palladium(II), which then undergoes reductive elimination to form the desired bis-aryl species as well as the starting Pd(0) complex, thus completing the catalytic cycle. | 0 | Organic Reactions |
Reduction by alkoxyaluminium hydrides is thought in most cases to proceed by a polar mechanism. Hydride transfer to the organic substrate generates an organic anion, which is neutralized either by protic solvent or upon acidic workup.
Reductions of α,β-unsaturated carbonyl compounds may occur in a 1,2 sense (direct addition) or a 1,4 sense (conjugate addition). The tendency to add in a 1,4 sense is correlated with the softness of the hydride reagent according to Pearson's hard-soft acid-base theory. Experimental results agree with the theory—softer hydride reagents afford higher yields of the conjugate reduction product.
A few substrates, including diaryl ketones, diarylalkenes, and anthracene, are known to undergo reduction by single-electron transfer pathways with lithium aluminium hydride.
Metal alkoxylaluminium hydride reagents are well characterized in a limited number of cases. Precise characterization is complicated in some cases by disproportionation, which converts alkyoxyaluminium hydrides into alkoxyaluminates and metal aluminium hydride:<br> | 0 | Organic Reactions |
The Crich β-mannosylation in organic chemistry is a synthetic strategy which is used in carbohydrate synthesis to generate a 1,2-cis-glycosidic bond. This type of linkate is generally very difficult to make, and specific methods like the Crich β-mannosylation are used to overcome these issues. The technique takes its name from its developer, Professor David Crich. | 0 | Organic Reactions |
These sterically constrained phosphorus compounds show remarkable reactivity towards protic reagents such as primary amines and alcohols, which results in intermolecular oxidative addition of these O−H and N−H bonds. This reaction tolerates a variety of different substrates, including ammonia and water. Two mechanisms have been suggested for the understanding of the unusual insertion of phosphorus atoms into polar X−H bonds by oxidative addition.
Nontrigonal phosphorus compounds can also react with ammonia–borane to form a formal dihydrogen oxidative addition product. This compound proved to facilitate the catalytic reduction of azobenzene. | 1 | Inorganic Reactions + Inorganic Compounds |
Because most heterocyclic bases contain multiple nucleophilic sites, site selectivity is an important issue in nucleoside synthesis. Purine bases, for instance, react kinetically at N and thermodynamically at N (see Eq. (4)). Glycosylation of thymine with protected 1-acetoxy ribose produced 60% of the N nucleoside and 23% of the N nucleoside. Closely related triazines, on the other hand, react with complete selectivity to afford the N nucleoside.
The most nucleophilic nitrogen can be blocked through alkylation prior to nucleoside synthesis. Heating the blocked nucleoside in Eq. (6) in the presence of a protected sugar chloride provides the nucleoside in 59% yield. Reactions of this type are hampered by alkylation of the heterocycle by incipient alkyl chloride.
Silylated heterocyclic bases are susceptible to hydrolysis and somewhat difficult to handle as a result; thus, the development of a one-pot, one-step method for silylation and nucleoside synthesis represented a significant advance. The combination of trifluoroacetic acid (TFA), trimethylsilyl chloride (TMSCl), and hexamethyldisilazide (HMDS) generates trimethylsilyl trifluoroacetate in situ, which accomplishes both the silylation of the heterocycle and its subsequent coupling with the sugar. | 0 | Organic Reactions |
The Crabbé reaction (or Crabbé allene synthesis, Crabbé–Ma allene synthesis) is an organic reaction that converts a terminal alkyne and aldehyde (or, sometimes, a ketone) into an allene in the presence of a soft Lewis acid catalyst (or stoichiometric promoter) and secondary amine. Given continued developments in scope and generality, it is a convenient and increasingly important method for the preparation of allenes, a class of compounds often viewed as exotic and synthetically challenging to access. | 0 | Organic Reactions |
The Baeyer–Emmerling indole synthesis is a method for synthesizing indole from a (substituted) ortho-nitrocinnamic acid and iron powder in strongly basic solution. This reaction was discovered by Adolf von Baeyer and Adolph Emmerling in 1869. | 0 | Organic Reactions |
The NS radical is a highly transient species, with a lifetime on the order of milliseconds, but it can be observed spectroscopically over short periods of time through several methods of generation. NS is too reactive to isolate as a solid or liquid, and has only been prepared as a vapor in low pressure or low-temperature matrices due to its tendency to rapidly oligomerize to more stable, diamagnetic species. | 1 | Inorganic Reactions + Inorganic Compounds |
Anhydrous can be prepared from zinc and hydrogen chloride gas at 700 °C:
Aqueous solutions may be readily prepared similarly by treating Zn metal, zinc carbonate, zinc oxide, and zinc sulfide with hydrochloric acid:
Hydrates can be produced by evaporation of an aqueous solution of zinc chloride. Different evaporation temperatures produce different hydrates; for example, evaporation at room temperature produces the 1.33-hydrate. Lower evaporation temperatures produce higher hydrates.
Commercial samples of zinc chloride typically contain water and products from hydrolysis as impurities. Such samples may be purified by recrystallization from hot dioxane. Anhydrous samples can be purified by sublimation in a stream of hydrogen chloride gas, followed by heating the sublimate to 400 °C in a stream of dry nitrogen gas. Finally, the simplest method relies on treating the zinc chloride with thionyl chloride. | 1 | Inorganic Reactions + Inorganic Compounds |
All elements aside from argon, neon, and helium form fluorides by direct reaction with fluorine. Chlorine is slightly more selective, but still reacts with most metals and heavier nonmetals. Following the usual trend, bromine is less reactive and iodine least of all. Of the many reactions possible, illustrative is the formation of gold(III) chloride by the chlorination of gold. The chlorination of metals is usually not very important industrially since the chlorides are more easily made from the oxides and hydrogen chloride. Where chlorination of inorganic compounds is practiced on a relatively large scale is for the production of phosphorus trichloride and disulfur dichloride. | 0 | Organic Reactions |
Trimethylenemethane cycloaddition is the formal (3+2) annulation of trimethylenemethane (TMM) derivatives to two-atom pi systems. Although TMM itself is too reactive and unstable to be stored, reagents which can generate TMM or TMM synthons in situ can be used to effect cycloaddition reactions with appropriate electron acceptors. Generally, electron-deficient pi bonds undergo cyclization with TMMs more easily than electron-rich pi bonds. | 0 | Organic Reactions |
In general, amino radicals are highly reactive and short lived; however, this is not the case when reacted with some organic molecules. Relative reactivities of the amino radical with several organic compounds have been reported, but the absolute rate constants for such reactions remain unknown. In reaction 1, it was hypothesized that the amino radical might possibly react with NH more rapidly than OH and might oxidize to produce the amino radical in acid solutions, given that radicals are stronger oxidants than OH. In order to test this, sulfate and phosphate radical anions were used. The sulfate and phosphate radical anions were found to react more slowly with NH than does the amino radical and they react with ammonia by hydrogen abstraction and not by electron transfer oxidation.
When the amino radical is reacted with benzoate ions, the rate constant is very low and only a weak absorption in the UV spectra is observed, indicating that amino radicals do not react with benzene rapidly. Phenol, on the other hand, was found to react more rapidly with the amino radical. In experiments at pH 11.3 and 12, using 1.5 M NH and varying concentrations of phenol between 4 and 10 mM, the formation of the phenoxyl radical absorption was observed with a rate constant of . This reaction can produce phenoxyl radicals via two possible mechanisms:
# Addition to the ring followed by elimination of NH, or
# Oxidation by direct electron transfer
While the amino radical is known to be weakly reactive, the recombination process of two amino radicals to form hydrazine appears to be one of the fastest. As a result, it often competes with other NH reactions.
:NH + NH → NH
At low pressures, this reaction is the fastest and therefore the principal mode of NH disappearance. | 1 | Inorganic Reactions + Inorganic Compounds |
The Tsuji–Trost reaction (also called the Trost allylic alkylation or allylic alkylation) is a palladium-catalysed substitution reaction involving a substrate that contains a leaving group in an allylic position. The palladium catalyst first coordinates with the allyl group and then undergoes oxidative addition, forming the -allyl complex. This allyl complex can then be attacked by a nucleophile, resulting in the substituted product.
This work was first pioneered by Jirō Tsuji in 1965 and, later, adapted by Barry Trost in 1973 with the introduction of phosphine ligands.
The scope of this reaction has been expanded to many different carbon, nitrogen, and oxygen-based nucleophiles, many different leaving groups, many different phosphorus, nitrogen, and sulfur-based ligands, and many different metals (although palladium is still preferred).
The introduction of phosphine ligands led to improved reactivity and numerous asymmetric allylic alkylation strategies. Many of these strategies are driven by the advent of chiral ligands, which are often able to provide high enantioselectivity and high diastereoselectivity under mild conditions. This modification greatly expands the utility of this reaction for many different synthetic applications. The ability to form carbon-carbon, carbon-nitrogen, and carbon-oxygen bonds under these conditions, makes this reaction very appealing to the fields of both medicinal chemistry and natural product synthesis. | 0 | Organic Reactions |
Among hindered dialkylboranes is disiamylborane, abbreviated SiaBH. It also is a dimer. Owing to its steric bulk, it selectively hydroborates less hindered, usually terminal alkenes in the presence of more substituted alkenes. Disiamylborane must be freshly prepared as its solutions can only be stored at 0 °C for a few hours. Dicyclohexylborane ChxBH exhibits improved thermal stability than SiaBH. | 0 | Organic Reactions |
Although the sodium cobaltinitrite is soluble in water, it forms the basis of a quantitative determination of potassium, thallium, and ammonium ions. Under the recommended reaction conditions the insoluble double salt, is precipitated and weighed. In geochemical analysis, sodium cobaltinitrite is used to distinguish alkali feldspars from plagioclase feldspars in thin section. | 1 | Inorganic Reactions + Inorganic Compounds |
Samarium(III) iodide is an inorganic compound, a salt of samarium and hydroiodic acid with the chemical formula . | 1 | Inorganic Reactions + Inorganic Compounds |
António Egas Moniz searched for a radiocontrast agent for cerebral angiography. After experiments on rabbits and dogs he settled upon sodium iodide as the best medium. | 1 | Inorganic Reactions + Inorganic Compounds |
In organic chemistry, alkylimino-de-oxo-bisubstitution is the organic reaction of carbonyl compounds with amines to imines. The reaction name is based on the IUPAC Nomenclature for Transformations. The reaction is acid catalyzed and the reaction type is nucleophilic addition of the amine to the carbonyl compound followed by transfer of a proton from nitrogen to oxygen to a stable hemiaminal or carbinolamine. With primary amines water is lost in an elimination reaction to an imine. With aryl amines especially stable Schiff bases are formed. | 0 | Organic Reactions |
Aromatic compounds are subject to electrophilic halogenation:
This kind of reaction typically works well for chlorine and bromine. Often a Lewis acidic catalyst is used, such as ferric chloride. Many detailed procedures are available.
Because fluorine is so reactive, other methods, such as the Balz–Schiemann reaction, are used to prepare fluorinated aromatic compounds. | 0 | Organic Reactions |
When heated, orthoboric acid undergoes a three step dehydration. The reported transition temperatures vary substantially from source to source.
When heated above 140 °C, orthoboric acid yields metaboric acid () with loss of one water molecule:
Heating metaboric acid above about 180 °C eliminates another water molecule forming tetraboric acid, also called pyroboric acid ():
Further heating (to about 530 °C) leads to boron trioxide: | 1 | Inorganic Reactions + Inorganic Compounds |