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The Michaelis–Becker reaction is the reaction of a hydrogen phosphonate with a base, followed by a nucleophilic substitution of phosphorus on a haloalkane, to give an alkyl phosphonate. Yields of this reaction are often lower than the corresponding Michaelis–Arbuzov reaction. | 0 | Organic Reactions |
Lanthanum(III) iodide is very soluble in water and is deliquescent. Anhydrous lanthanum(III) iodide reacts with tetrahydrofuran to form a photoluminescent complex, LaI(THF), with an average La–I bond length of 3.16 Å. This complex is a starting material for amide and cyclopentadienyl complexes of lanthanum. | 1 | Inorganic Reactions + Inorganic Compounds |
Molecules in distant astronomical regions can be identified based on their unique rotational transitions, of which the corresponding microwave frequencies are detectable by antennae on Earth. The presence of interstellar sulfur mononitride was first reported in 1975 by back to back letters published in the Astrophysical Journal.
Interstellar NS was first identified in the giant molecular cloud Sagittarius B2 (Sgr B2). Its presence was reported in two concurrent articles. Measurements conducted with the National Radia Astronomy Observatory telescope at Kitt Peak, Arizona, picked up millimeter-wavelength radiation in Sgr B2 attributed to c-state transitions of NS in the Π state from J=5/2 to J=3/2 at 115.16 GHz. This assignment was confirmed by measurements conducted at University of Texas Millimeter Wave Observatory on Mount Locke as well, demonstrating J=5/2 to J=3/2 c-state and d-state transitions at 115.16 GHz and 115.6 GHz, respectively. Hyperfine interactions arise from N magnetic and electric-quadrupole moments.
NS has been detected in regions responsible for forming massive stars, such as giant molecular clouds like Sg B2 and cold, dark clouds such as L134N and TMC-1. One survey found NS in 12 out of 14 GMC studied, additionally observing the J=7/2 to J=5/2 and J=3/2 to J=1/2 transitions at 161 and 69 GHz, respectively. The abundance of NS in these regions was approximated based on the ratio of observed to intrinsic hyperfine line strengths as well as modeling using a statistical equilibrium program, finding low abundance in all except the Orion molecular cloud.
NS was also observed in the coma of the comets Hyakutake and Hale-Bopp. It's believed that the observed abundance is higher than gas-phase, ion-molecule models due to an unidentified species X-NS photo-dissociating to release NS. | 1 | Inorganic Reactions + Inorganic Compounds |
LSAT is the most common name for the inorganic compound lanthanum aluminate - strontium aluminium tantalate, which has the chemical formula (LaAlO)(SrTaAlO) or its less common alternative: (LaSr)(AlTa)O. LSAT is a hard, optically transparent oxide of the elements lanthanum, aluminium, strontium and tantalum. LSAT has the perovskite crystal structure, and its most common use is as a single crystal substrate for the growth of epitaxial thin films. | 1 | Inorganic Reactions + Inorganic Compounds |
Cadmium sulfide is toxic, especially dangerous when inhaled as dust, and cadmium compounds in general are classified as carcinogenic. Problems of biocompatibility have been reported when CdS is used as colors in tattoos. CdS has an LD of approximately 7,080 mg/kg in rats - which is higher than other cadmium compounds due to its low solubility. | 1 | Inorganic Reactions + Inorganic Compounds |
The advantage of “arming” and “disarming” glycosyl donors lies in their synthetic use. By disarming the glycosyl, a selective coupling can be achieved. The disarmed portion of the disaccharide can then be armed through selective deprotection. The disaccharide can then be coupled to a disarmed sugar. This process can be repeated as many times as necessary to achieve an efficient synthesis of a desired oligosaccharide with minimal loss of material to undesired coupling. This can be especially useful in “one-pot” synthetic methods. In these methods, multiple sugars are added to the reaction mixture. One of the sugars is armed as the glycosyl donor, and reacts quickly with a glycosyl acceptor. The non-reducing sugar then acts as a glycosyl acceptor as a protecting group that is easily lost in solution reveals a free hydroxyl group. This reacts with a donor that was disarmed, forming the oxocarbenium ion at a slower rate, producing the desired trisaccharide. | 0 | Organic Reactions |
The Enders SAMP/RAMP hydrazone alkylation begins with the synthesis of the hydrazone from a N,N-dialkylhydrazine and a ketone or aldehyde
The hydrazone is then deprotonated on the α-carbon position by a strong base, such as lithium diisopropylamide (LDA), leading to the formation of a resonance stabilized anion - an azaenolate. This anion is a very good nucleophile and readily attacks electrophiles, such as alkyl halides, to generate alkylated hydrazones with simultaneous creation of a new chiral center at the α-carbon.
The stereochemistry of this reaction is discussed in detail in next section. | 0 | Organic Reactions |
Electrophilic, soluble alkylating agents are often toxic and carcinogenic, due to their tendency to alkylate DNA. This mechanism of toxicity is relevant to the function of anti-cancer drugs in the form of alkylating antineoplastic agents. Some chemical weapons such as mustard gas (sulfide of dichloroethyl) function as alkylating agents. Alkylated DNA either does not coil or uncoil properly, or cannot be processed by information-decoding enzymes. | 0 | Organic Reactions |
The IUPAC nomenclature systematically naming nitrogen compounds by identifying hydronitrogen chains, analogous to the alkane nomenclature. Unbranched, saturated hydronitrogen chains are named with a Greek numerical prefix for the number of nitrogens and the suffix "-azane" for hydronitrogens with single bonds, or "-azene" for those with double bonds. | 1 | Inorganic Reactions + Inorganic Compounds |
Monoalkyl boranes are relatively rare. When the alkyl group is small, such as methyl, the monoalkylboranes tend to redistribute to give mixtures of diborane and di- and trialkylboranes. Monoalkylboranes typically exist as dimers of the form [RBH]. One example is thexylborane (ThxBH), produced by the hydroboration of tetramethylethylene:
:BH + 2 MeC=CMe → [MeCHCMeBH]
A chiral example is monoisopinocampheylborane. Although often written as IpcBH, it is a dimer [IpcBH]. It is obtained by hydroboration of (−)‐α‐pinene with borane dimethyl sulfide.
Species of the form RBH are available for R = alkyl and halide. Monobromo- and monochloro-borane can be prepared from BMS and the corresponding boron trihalides. The stable complex of monochloroborane and 1,4-dioxane effects hydroboration of terminal alkenes. | 0 | Organic Reactions |
The molecular structures of nontrigonal pnictogen compounds reveal the steric strain in these molecules, and significantly differing bond angles at the pnictogen atoms indicate a considerable distortion of the coordination spheres.
In particular, the geometry at the central part of these compounds deviate strongly from traditional pnictogen compounds, and indicate molecular strain with an approach to a T-type molecular configuration. With different ligand motifs, the bond angles at pnictogen atoms can vary from 100˚ to almost 180˚. The flattened geometry of these molecules influences the relatively low energetic barriers for inversion of the configuration via planar coordinated pnictogen atoms in the transition state. These low barriers are in accordance with the dynamic behavior and fast equilibration processes observed in ambient temperature NMR.
Results of quantum chemical calculations confirm that in these compounds, the lone pair of electrons at the pnictogen atoms is localized in orbitals with relatively high s-character. From these results, only weak nucleophilicity was derived in accordance with some experimental observations such as the inertness towards benzyl bromide. The LUMO is delocalized but has important contributions from pnictogen empty p orbitals, which should favor a nucleophilic attack of substrates at this position in accordance with experimental findings. The pnictogen atom forms a three-center-four-electron bond with the two flanking nitrogen atoms, which is manifested by the HOMO-2.
For nontrigonal bismuth compounds, a Bi(I) electronic structure could be shown to be most appropriate. Natural bond orbital (NBO) analysis reveals an s-type lone pair and a p-type lone pair at the metal, with the remaining two p orbitals being involved in one two-center-two-electron bond and one three-center-two-electron bond. The p-type lone pair NBO has less than 2 electron occupancy as it is delocalized over the ligand frame. Although considerable Bi(I) character is indicated for the Bi compound, it exhibits reactivity similar to Bi(III) electrophiles, and expresses either a vacant or a filled p orbital at Bi.
From these results, two types of resonance structures can be drawn, one with a filled s-orbital and a vacant p orbital at the pnictogen center, the other one with negative charge on pnictogen, arising from the redox-non-innocent nature of the ligand. This is evident by shorter C-N bond lengths in nontrigonal pnictogen compounds than C-N single bonds in the corresponding ligands. These structures may reflect the specific bonding situation in these strained molecular systems. | 1 | Inorganic Reactions + Inorganic Compounds |
Trifluoromethylation in organic chemistry describes any organic reaction that introduces a trifluoromethyl group in an organic compound. Trifluoromethylated compounds are of some importance in pharmaceutical industry and agrochemicals. Several notable pharmaceutical compounds have a trifluoromethyl group incorporated: fluoxetine, mefloquine, Leflunomide, nulitamide, dutasteride, bicalutamide, aprepitant, celecoxib, fipronil, fluazinam, penthiopyrad, picoxystrobin, fluridone, norflurazon, sorafenib and triflurazin. A relevant agrochemical is trifluralin. The development of synthetic methods for adding trifluoromethyl groups to chemical compounds is actively pursued in academic research. | 0 | Organic Reactions |
A variety of heteroatom-containing substituents promote lateral lithiation of an ortho methyl group. Generally, better results are obtained when the heteroatom is in the β position rather than the α position, as the latter tends to promote ortho lithiation. Lithation of primary benzylic positions is slower than lithiation of methyl groups due to inductive electron donation from the additional alkyl group (rather than steric effects). Electrophiles that react with the benzylic anions formed by these methods include aldehydes and ketones, activated (primary, allylic, or benzylic) halides, molecular oxygen, and silyl chlorides. This section describes the scope of directing groups that may be used to effect site-selective lithiation in substituted benzenes and heterocycles. | 0 | Organic Reactions |
In organic chemistry glycerolysis refers to any process in which chemical bonds are broken via a reaction with glycerol. The term refers almost exclusively to the transesterification reaction of glycerol with triglycerides (fats/oils) to form mixtures of monoglycerides and diglycerides. These find a variety of uses; as food emulsifiers (e.g. E471), low fat cooking oils (e.g. diacylglycerol oil) and surfactants (such as monolaurin).
The transesterification process gives a complex mixture of products, however not all of these are of equivalent use. This has led to the development of optimized processes able to produce better defined products; in particular by using enzymes, reactions in supercritical carbon dioxide and flow chemistry. The production of diglycerides (often called diacylglycerols or DAGs) have been investigated extensively due to their use in foods, with total annual sales of approximately US$200 million in Japan since its introduction in the late 1990s until 2009. | 0 | Organic Reactions |
Digallane (systematically named digallane(6)) is an inorganic compound with the chemical formula (also written or ). It is the dimer of the monomeric compound gallane. The eventual preparation of the pure compound, reported in 1989,
was hailed as a "tour de force." Digallane had been reported as early as 1941 by Wiberg; however, this claim could not be verified by later work by Greenwood and others. This compound is a colorless gas that decomposes above 0 °C.
__TOC__ | 1 | Inorganic Reactions + Inorganic Compounds |
Potassium bifluoride is the inorganic compound with the formula . This colourless salt consists of the potassium cation () and the bifluoride anion (). The salt is used as an etchant for glass. Sodium bifluoride is related and is also of commercial use as an etchant as well as in cleaning products. | 1 | Inorganic Reactions + Inorganic Compounds |
It can be produced by heating KSO with carbon (coke):
:KSO + 4 C → KS + 4 CO
In the laboratory, pure KS may be prepared by the reaction of potassium and sulfur in anhydrous ammonia.
Sulfide is highly basic, consequently KS completely and irreversibly hydrolyzes in water according to the following equation:
:KS + HO → KOH + KSH
For many purposes, this reaction is inconsequential since the mixture of SH and OH behaves as a source of S. Other alkali metal sulfides behave similarly. | 1 | Inorganic Reactions + Inorganic Compounds |
Miura et al. reported the cross coupling of vinyl bromides with an alkenyl carboxylic acid using a palladium catalyst. Some of the conjugated dienes prepared were reported to exhibit solid state fluorescence. | 0 | Organic Reactions |
Hydrogen cyanide was first isolated from a blue pigment (Prussian blue) which had been known since 1706, but whose structure was unknown. It is now known to be a coordination polymer with a complex structure and an empirical formula of hydrated ferric ferrocyanide. In 1752, the French chemist Pierre Macquer made the important step of showing that Prussian blue could be converted to an iron oxide plus a volatile component and that these could be used to reconstitute it. The new component was what is now known as hydrogen cyanide. Following Macquers lead, it was first prepared from Prussian blue by the Swedish chemist Carl Wilhelm Scheele in 1782, and was eventually given the German name Blausäure (lit. "Blue acid") because of its acidic nature in water and its derivation from Prussian blue. In English, it became known popularly as prussic acid.'
In 1787, the French chemist Claude Louis Berthollet showed that prussic acid did not contain oxygen, an important contribution to acid theory, which had hitherto postulated that acids must contain oxygen (hence the name of oxygen itself, which is derived from Greek elements that mean "acid-former" and are likewise calqued into German as Sauerstoff). In 1811, Joseph Louis Gay-Lussac prepared pure, liquified hydrogen cyanide. In 1815, Gay-Lussac deduced Prussic acids chemical formula. The radical cyanide' in hydrogen cyanide was given its name from cyan, not only an English word for a shade of blue but the Greek word for blue (), again owing to its derivation from Prussian blue. | 1 | Inorganic Reactions + Inorganic Compounds |
Cobalt chloride is fairly soluble in water. Under atmospheric pressure, the mass concentration of a saturated solution of in water is about 54% at the boiling point, 120.2 °C; 48% at 51.25 °C; 35% at 25 °C; 33% at 0 °C; and 29% at −27.8 °C.
Diluted aqueous solutions of contain the species , besides chloride ions. Concentrated solutions are red at room temperature but become blue at higher temperatures. | 1 | Inorganic Reactions + Inorganic Compounds |
Methane was premixed with fuel in the form of either O, NO, or air and burned at ambient pressure. The source of nitrogen was introduced by addition of 1-5 mole% NH gas and sulfur by 0.01-0.5 mol% HS or SF gas. A steady state concentration of NS within the flame front is observed by laser-induced fluorescence (LIF) spectrum. | 1 | Inorganic Reactions + Inorganic Compounds |
The Helferich method may refer to:
#Glycosylation of an alcohol using a glycosyl acetate as glycosyl donor and a Lewis acid (e.g. a metal halide) as promoter
#Glycosylation of an alcohol using a glycosyl halide as a glycosyl donor and a mercury salt as promoter (cf the Koenigs-Knorr reaction, which uses silver salts as promoters). | 0 | Organic Reactions |
A glycosyl donor is a carbohydrate mono- or oligosaccharide that will react with a suitable glycosyl acceptor to form a new glycosidic bond. By convention, the donor is the member of this pair that contains the resulting anomeric carbon of the new glycosidic bond. The resulting reaction is referred to as a glycosylation or chemical glycosylation.
In a glycosyl donor, a leaving group is required at the anomeric position. The simplest leaving group is the OH group that is naturally present in monosaccharides, but it requires activation by acid catalysis in order to function as leaving group (in the Fischer glycosylation). More effective leaving groups are in general used in the glycosyl donors employed in chemical synthesis of glycosides. Typical leaving groups are halides, thioalkyl groups, or imidates, but acetate, phosphate, and O-pentenyl groups are also employed. Natural glycosyl donors contain phosphates as leaving groups.
The so-called “armed-disarmed” principle
The concept of armed and disarmed glycosyl donors refers to the increased reactivity of benzylated over benzoylated glycosyl donors, a phenomenon observed very early, and which originates from the greater electron-withdrawing capability of ester blocking groups over ether blocking groups. However, it was Bertram Fraser-Reid who realised that benzylated glycosyl donors can be activated when benzoylated donors are not, and invented the terms armed glycosyl donor for the former, and disarmed glycosyl donor for the latter. He and his group showed that armed glycosyl donors could be coupled to a glycosyl acceptor, that was at the same time a disarmed glycosyl donor, without self-coupling of the disarmed donor/acceptor. This approach allowed him to carry out a one-pot synthesis of a trisaccharide by the n-pentenyl glycoside method.
The concept has been extended to superarmed glycosyl donor by Mikael Bols and his collaborators. He realised that the hydroxy groups of carbohydrates are less electron-withdrawing towards the anomeric center when they are axial than when they are equatorial, which means that glycosyl donor conformers with more axial oxy functions are more reactive. Protection of a glycosyl donor with bulky silyl groups (tert-butyldimethylsilyl or triisopropyl) cause it to change conformation to a more axial-rich conformation that, as a consequence, is more reactive, which Bols and his group called superarmed. They showed that a superarmed donor can be coupled to an armed glycosyl donor/acceptor. | 0 | Organic Reactions |
The most well-known example of a coarctate transition state is that of the epoxidation of an olefin by dimethyldioxirane. In this transition state, the oxygen atom transferred to the olefin forms a cycle with the acetone leaving group and a cycle with the olefin undergoing epoxidation. Another well-studied reaction is the fragmentation of spirocyclic ozonides into formaldehyde, CO, and an olefin.
Selection rules, resembling the Woodward-Hoffmann rules, have been proposed to explain patterns in reaction activation energy related to transition state topology or orbital symmetry. | 0 | Organic Reactions |
Borate esters are organic compounds, which are conveniently prepared by the stoichiometric condensation reaction of boric acid with alcohols (or their chalcogen analogs). | 1 | Inorganic Reactions + Inorganic Compounds |
The Payne rearrangement occurs with inversion of stereochemistry at C-2. Substrates containing multiple adjacent hydroxyl groups may undergo "cascade" epoxide migrations with inversion at each site of nucleophilic attack. In one example, inversion of three contiguous stereocenters results after two epoxide migrations, opening of the epoxide by carboxylate, and hydrolysis of the resulting lactone. | 0 | Organic Reactions |
The WGSR has been extensively studied for over a hundred years. The kinetically relevant mechanism depends on the catalyst composition and the temperature. Two mechanisms have been proposed: an associative Langmuir–Hinshelwood mechanism and a redox mechanism. The redox mechanism is generally regarded as kinetically relevant during the high-temperature WGSR (> 350 °C) over the industrial iron-chromia catalyst. Historically, there has been much more controversy surrounding the mechanism at low temperatures. Recent experimental studies confirm that the associative carboxyl mechanism is the predominant low temperature pathway on metal-oxide-supported transition metal catalysts. | 1 | Inorganic Reactions + Inorganic Compounds |
Carboamination is an efficient method to access nitrogen-containing molecules, especially N-heterocycles. (+)-Preussin, a pyrrolidine alkaloid, can be easily prepared via this methodology.
(–)-Tylophorine is another example, which can be synthesized using carboamination reaction. | 0 | Organic Reactions |
Because the Edman degradation proceeds from the N-terminus of the protein, it will not work if the N-terminus has been chemically modified (e.g. by acetylation or formation of pyroglutamic acid). Sequencing will stop if a non-α-amino acid is encountered (e.g. isoaspartic acid), since the favored five-membered ring intermediate is unable to be formed. Edman degradation is generally not useful to determine the positions of disulfide bridges. It also requires peptide amounts of 1 picomole or above for discernible results. | 0 | Organic Reactions |
The asymmetric hydrogenation of indoles has been established with N-Boc protection.
<br />
A Pd(TFA)/H8-BINAP system achieves the enantioselective cis-hydrogenation of 2,3- and 2-substituted indoles.
<br />
Akin to the behavior of indoles, pyrroles can be converted to pyrrolidines by asymmetric hydrogenation.
<br /> | 0 | Organic Reactions |
Decarboxylative cross coupling reactions are chemical reactions in which a carboxylic acid is reacted with an organic halide to form a new carbon-carbon bond, concomitant with loss of CO. Aryl and alkyl halides participate. Metal catalyst, base, and oxidant are required.
A significant advantage of this reaction is that it uses relatively inexpensive carboxylic acids (or their salts) and is far less air and moisture sensitive in comparison to typical cross-coupling organometallic reagents. Furthermore, the carboxylic acid moiety is a common feature of natural products and can also be prepared by relatively benign air oxidations. Additional benefits include the broad tolerance of functional groups, as well as the capacity to avoid the use of strong bases. An important elementary step in this reaction is protodecarboxylation or metalation to first convert the C–COOH bond to a C–H or C–M bond respectively. | 0 | Organic Reactions |
For catalytic hydroboration, pinacolborane and catecholborane are widely used. They also exhibit higher reactivity toward alkynes. Pinacolborane is also widely used in a catalyst-free hydroborations. | 0 | Organic Reactions |
In the solid state of their salts, metaborate ions are often oligomeric or polymeric, conceptually resulting from the fusion of two or more through shared oxygen atoms. In these anions, the boron atom forms covalent bonds with either three or four oxygen atoms. Some of the structures are:
* A trimer with formula or , consisting of a six-membered ring of alternating boron and oxygen atoms with one extra oxygen atom attached to each boron atom. This form is found, for example, in some anhydrous alkali metal salts like sodium metaborate or potassium metaborate, in α- and β-barium metaborate , and in the mixed salt potassium cadmium metaborate . The three B–O distances are nearly equal in the potassium salt (133.1, 139.8, and 139.8 pm) but significantly different in the sodium one (128.0, 143.3, and 143.3 pm).
* A polymer of units connected by single shared-oxygen bridges; that is, . Occurs in calcium metaborate or .
* A tridimensional network of tetrahedral groups, as in "zinc metaborate", which is actually a mixed salt zinc metaborate oxide, with the formula .
* A tridimensional regular array of tetrahedra sharing oxygen vertices, as in the high-pressure and high-temperature γ form of lithium metaborate . | 1 | Inorganic Reactions + Inorganic Compounds |
Similar principles guide the lowest energy conformations of larger ring systems. Along with the acyclic stereocontrol principles outlined below, subtle interactions between remote substituents in large rings, analogous to those observed for 8-10 membered rings, can influence the conformational preferences of a molecule. In conjunction with remote substituent effects, local acyclic interactions can also play an important role in determining the outcome of macrocyclic reactions. The conformational flexibility of larger rings potentially allows for a combination of acyclic and macrocyclic stereocontrol to direct reactions. | 0 | Organic Reactions |
Reactions involving palladium(II) acetate and phosphine ligands proceed by a third mechanism, the anionic pathway. Base mediates the oxidation of a phosphine ligand by palladium(II) to a phosphine oxide. Oxidative addition then generates the anionic palladium complex IX. Loss of halide leads to neutral complex X, which undergoes steps analogous to the neutral pathway to regenerate anionic complex IX. A similar anionic pathway is also likely operative in reactions of bulky palladium tri(tert-butyl)phosphine complexes. | 0 | Organic Reactions |
Praseodymium(III) oxalate is used as an intermediate product in the synthesis of praseodymium. It is also applied to colour some glasses and enamels. If mixed with certain other materials, the compound paints glass intense yellow. | 1 | Inorganic Reactions + Inorganic Compounds |
In hydrothermal liquefaction processes, long carbon chain molecules in biomass are thermally cracked and oxygen is removed in the form of HO (dehydration) and CO (decarboxylation). These reactions result in the production of high H/C ratio bio-oil. Simplified descriptions of dehydration and decarboxylation reactions can be found in the literature (e.g. Asghari and Yoshida (2006) and Snåre et al. (2007). | 0 | Organic Reactions |
Hydrogen bromide (along with hydrobromic acid) is produced by combining hydrogen and bromine at temperatures between 200 and 400 °C. The reaction is typically catalyzed by platinum or asbestos. | 1 | Inorganic Reactions + Inorganic Compounds |
HDAC11 has been shown to be related to HDACs 3 and 8, but its overall sequence is quite different from the other HDACs, leading it to be in its own category. HDAC11 has a catalytic domain located in its N-terminus. It has not been found incorporated in any HDAC complexes such as Nurd or SMRT which means it may have a special function unique to itself. It has been found that HDAC11 remains mainly in the nucleus. | 0 | Organic Reactions |
Sodium hydroxide is traditionally used in soap making (cold process soap, saponification). It was made in the nineteenth century for a hard surface rather than liquid product because it was easier to store and transport.
For the manufacture of biodiesel, sodium hydroxide is used as a catalyst for the transesterification of methanol and triglycerides. This only works with anhydrous sodium hydroxide, because combined with water the fat would turn into soap, which would be tainted with methanol. NaOH is used more often than potassium hydroxide because it is cheaper and a smaller quantity is needed. Due to production costs, NaOH, which is produced using common salt is cheaper than potassium hydroxide. | 1 | Inorganic Reactions + Inorganic Compounds |
A particularly common α-substitution reaction in the laboratory is the halogenation of aldehydes and ketones at their α positions by reaction Cl, Br or I in acidic solution. Bromine in acetic acid solvent is often used.
Remarkably, ketone halogenation also occurs in biological systems, particularly in marine alga, where , bromoacetone, , and other related compounds have been found.
The halogenation is a typical α-substitution reaction that proceeds by acid catalyzed formation of an enol intermediate. | 0 | Organic Reactions |
Lanthanum also forms a diiodide, LaI. It is an electride and is best formulated {La,2I,e}, with the electron delocalised in a conduction band. Several other lanthanides form similar compounds, including CeI, PrI and GdI. Lanthanum diiodide adopts the same tetragonal crystal structure as PrI.
Lanthanum(III) iodide reacts with lanthanum metal under an argon atmosphere in a tantalum capsule at 1225 K to form the mixed-valence compound LaI.
Reduction of LaI or LaI with metallic sodium in an argon atmosphere at 550 °C gives lanthanum monoiodide, LaI, which has a hexagonal crystal structure. | 1 | Inorganic Reactions + Inorganic Compounds |
Lead azide in its pure form was first prepared by Theodor Curtius in 1891. Due to sensitivity and stability concerns, the dextrinated form of lead azide (MIL-L-3055) was developed in the 1920s and 1930s with large scale production by DuPont Co beginning in 1932. Detonator development during World War II resulted in the need for a form of lead azide with a more brisant output. RD-1333 lead azide (MIL-DTL-46225), a version of lead azide with sodium carboxymethyl cellulose as a precipitating agent, was developed to meet that need. The Vietnam War saw an accelerated need for lead azide and it was during this time that Special Purpose Lead Azide (MIL-L-14758) was developed; the US government also began stockpiling lead azide in large quantities. After the Vietnam War, the use of lead azide dramatically decreased. Due to the size of the US stockpile, the manufacture of lead azide in the US ceased completely by the early 1990s. In the 2000s, concerns about the age and stability of stockpiled lead azide led the US government to investigate methods to dispose of its stockpiled lead azide and obtain new manufacturers. | 1 | Inorganic Reactions + Inorganic Compounds |
Trimethylboroxine is used in the methylation of various aryl halides through palladium-catalyzed Suzuki-Miyaura coupling reactions:
Another form of the Suzuki-Miyaura coupling reaction exhibits selectivity to aryl chlorides:
Boroxines have also been examined as precursors to monomeric oxoborane, HB≡O. This compound quickly converts back to the cyclic boroxine, even at low temperatures. | 1 | Inorganic Reactions + Inorganic Compounds |
Methylation sometimes involve use of nucleophilic methyl reagents. Strongly nucleophilic methylating agents include methyllithium () or Grignard reagents such as methylmagnesium bromide (). For example, will add methyl groups to the carbonyl (C=O) of ketones and aldehyde.:
Milder methylating agents include tetramethyltin, dimethylzinc, and trimethylaluminium. | 0 | Organic Reactions |
The WGSR is a highly valuable industrial reaction that is used in the manufacture of ammonia, hydrocarbons, methanol, and hydrogen. Its most important application is in conjunction with the conversion of carbon monoxide from steam reforming of methane or other hydrocarbons in the production of hydrogen. In the Fischer–Tropsch process, the WGSR is one of the most important reactions used to balance the H/CO ratio. It provides a source of hydrogen at the expense of carbon monoxide, which is important for the production of high purity hydrogen for use in ammonia synthesis.
The water–gas shift reaction may be an undesired side reaction in processes involving water and carbon monoxide, e.g. the rhodium-based Monsanto process. The iridium-based Cativa process uses less water, which suppresses this reaction. | 1 | Inorganic Reactions + Inorganic Compounds |
Amine alkylation (amino-dehalogenation) is a type of organic reaction between an alkyl halide and ammonia or an amine. The reaction is called nucleophilic aliphatic substitution (of the halide), and the reaction product is a higher substituted amine. The method is widely used in the laboratory, but less so industrially, where alcohols are often preferred alkylating agents.
When the amine is a tertiary amine the reaction product is a quaternary ammonium salt in the Menshutkin reaction:
Amines and ammonia are generally sufficiently nucleophilic to undergo direct alkylation, often under mild conditions. The reactions are complicated by the tendency of the product (a primary amine or a secondary amine) to react with the alkylating agent. For example, reaction of 1-bromooctane with ammonia yields almost equal amounts of the primary amine and the secondary amine. Therefore, for laboratory purposes, N-alkylation is often limited to the synthesis of tertiary amines. An exception is the amination of alpha-halo carboxylic acids that do permit synthesis of primary amines with ammonia. Intramolecular reactions of haloamines X-(CH)-NH give cyclic aziridines, azetidines and pyrrolidines.
N-alkylation is a general and useful route to quaternary ammonium salts from tertiary amines, because overalkylation is not possible.
Examples of N-alkylation with alkyl halides are the syntheses of benzylaniline, 1-benzylindole, and azetidine. Another example is found in the derivatization of cyclen. Industrially, ethylenediamine is produced by alkylation of ammonia with 1,2-dichloroethane. | 0 | Organic Reactions |
The nucleophiles used are typically generated from precursors (pronucleophiles) in situ after their deprotonation with base. These nucleophiles are then subdivided into "hard" and "soft" nucleophiles using a paradigm for describing nucleophiles that largely rests on the Acid dissociation constant| of their conjugate acids. "Hard" nucleophiles typically have conjugate acids with greater than 25, while "soft" nucleophiles typically have conjugate acids with less than 25.
This descriptor is important because of the impact these nucleophiles have on the stereoselectivity of the product. Stabilized or "soft" nucleophiles invert the stereochemistry of the -allyl complex. This inversion in conjunction with the inversion in stereochemistry associated with the oxidative addition of palladium yields a net retention of stereochemistry. Unstabilized or "hard" nucleophiles, on the other hand, retain the stereochemistry of the -allyl complex, resulting in a net inversion of stereochemistry.
This trend is explained by examining the mechanisms of nucleophilic attack. "Soft" nucleophiles attack the carbon of the allyl group, while "hard" nucleophiles attack the metal center, followed by reductive elimination. | 0 | Organic Reactions |
Tetraselenium tetranitride is the inorganic compound with the formula . Like the analogous tetrasulfur tetranitride , is an orange solid. It is however less soluble and more shock-sensitive than .
As determined by X-ray crystallography, adopts a cage structure similar to that of . The Se−Se and Se−N distances are 2.740 and 1.800 Å, respectively. The N−Se−N angles are 90°.
Among its many reactions, reacts with aluminium chloride to form adducts of . | 1 | Inorganic Reactions + Inorganic Compounds |