Americium(III) oxide

Americium(III) oxide or americium sesquioxide is an oxide of the element americium. It has the empirical formula Am2O3. Since all isotopes of americium are only artificially produced, americium (III) oxide has no natural occurrence. The colour depends on the crystal structure, of which there are more than one. It is soluble in acids.
Formation.
Americium(III) oxide can be made by heating americium dioxide in hydrogen at 600°C.
Forms.
The hexagonal form is coloured tan, and the cubic form is coloured red-brown the same as persimmon. The cubic form converts to the hexagonal form on heating to 800°C. The cubic form is non-stoichimetric with variable oxygen composition. It darkens with increasing oxygen.


Indium trihydride

Indium trihydride is an inorganic compound with the chemical formula (). It has been observed in matrix isolation and laser ablation experiments. Gas phase stability has been predicted. The infrared spectrum was obtained in the gas phase by laser ablation of indium in presence of hydrogen gas InH3 is of no practical importance
Chemical properties.
Solid InH3 is a three-dimensional network polymeric structure, where In atoms are connected by In-H-In bridging bonds, is suggested to account for the growth of broad infrared bands when samples of InH3 and InD3 produced on a solid hydrogen matrix are warmed. Such a structure is known for solid AlH3. When heated above , indium trihydride decomposes to produce indium–hydrogen alloy and elemental hydrogen. As of 2013, the only known method of synthesising indium trihydride is the autopolymerisation of indane below .
Other indium hydrides.
Several compounds with In-H bonds have been reported. Examples of complexes with two hydride ligands replaced by other ligands are K3[K(Me2SiO)7][HIn(Me3CCH2)3]4 and HIn(2-Me2NCH2-C6H4)2.
Although InH3 is labile, adducts are known with the stoichiometry InH3Ln (n = 1 or 2).
1:1 amine adducts are made by the reaction of LiInH4 with a trialkylammonium salt. The trimethylamine complex is only stable below −30 °C or in dilute solution. The 1:1 and 1:2 complexes with tricyclohexylphosphine (PCy3) have been characterised crystallographically. The average In-H bond length is 168 pm. Indium hydride is also known to form adducts with NHCs.


Monoethanolamine oleate

Monoethanolamine oleate (properly ethanolammonium oleate) is an antivaricose agent. It is a salt formed by Lowry–Brønsted acid–base reaction between monoethanolamine and oleic acid, is systematically named 2-hydroxyethylammonium (9"Z")-octadecenoate, and has a structural formula [CH3(CH2)7CH=CH(CH2)7CO2][H3NCH2CH2OH]. It is injected topically into varicosities to cause sclerosis (closure) of the abnormal vein.
Uses.
Ethanolamine Oleate (Ethanolamin) injection is indicated for the treatment of patients with esophageal varices that have recently bled, to prevent rebleeding.
Ethanolamin is not indicated for the treatment of patients with esophageal varices that have not bled. There is no evidence that treatment of this population decreases the likelihood of bleeding.
Sclerotherapy with Ethanolamin has no beneficial effect upon portal hypertension, the cause of esophageal varices, so that recanalization and collateralization may occur, necessitating reinjection.


Isotopes of palladium

Naturally occurring palladium (46Pd) is composed of six stable isotopes, 102Pd, 104Pd, 105Pd, 106Pd, 108Pd, and 110Pd, although 102Pd and 110Pd are theoretically unstable. The most stable radioisotopes are 107Pd with a half-life of 6.5 million years, 103Pd with a half-life of 17 days, and 100Pd with a half-life of 3.63 days. Twenty-three other radioisotopes have been characterized with atomic weights ranging from 90.949 u (91Pd) to 128.96 u (129Pd). Most of these have half-lives that are less than a half an hour except 101Pd (half-life: 8.47 hours), 109Pd (half-life: 13.7 hours), and 112Pd (half-life: 21 hours).
The primary decay mode before the most abundant stable isotope, 106Pd, is electron capture and the primary mode after is beta decay. The primary decay product before 106Pd is rhodium and the primary product after is silver.
Radiogenic 107Ag is a decay product of 107Pd and was first discovered in the Santa Clara meteorite of 1978. The discoverers suggest that the coalescence and differentiation of iron-cored small planets may have occurred 10 million years after a nucleosynthetic event. 107Pd versus Ag correlations observed in bodies, which have clearly been melted since accretion of the solar system, must reflect the presence of short-lived nuclides in the early solar system.
Palladium-103.
Palladium-103 is a radioisotope of the element palladium that has uses in radiation therapy for prostate cancer and uveal melanoma. Palladium-103 may be created from palladium-102 or from rhodium-103 using a cyclotron. Palladium-103 has a half-life of 16.99 days and decays by electron capture to rhodium-103, emitting characteristic x-rays with 21 keV of energy.
Palladium-107.
Palladium-107 is the second-longest lived (half-life of 6.5 million years) and least radioactive (decay energy only 33 keV, specific activity 5 Ci/g) of the 7 long-lived fission products. It undergoes pure beta decay (without gamma radiation) to 107Ag, which is stable.
Its yield from thermal neutron fission of uranium-235 is 0.1629% per fission, only 1/4 that of iodine-129, and only 1/40 those of 99Tc, 93Zr, and 135Cs. Yield from 233U is slightly lower, but yield from 239Pu is much higher, 3.3%. Fast fission or fission of some heavier actinides"[which?]" will produce palladium-107 at higher yields.
One source estimates that palladium produced from fission contains the isotopes 104Pd (16.9%),105Pd (29.3%), 106Pd (21.3%), 107Pd (17%), 108Pd (11.7%) and 110Pd (3.8%). According to another source, the proportion of 107Pd is 9.2% for palladium from thermal neutron fission of 235U, 11.8% for 233U, and 20.4% for 239Pu (and the 239Pu yield of palladium is about 10 times that of 235U).
Because of this dilution and because 105Pd has 11 times the neutron absorption cross section, 107Pd is not amenable to disposal by nuclear transmutation. However, as a noble metal, palladium is not as mobile in the environment as iodine or technetium.


Mercury methylation

Mercury methylation is the process of forming methylmercury (MeHg). The methylation of mercury can occur abiotically or biotically. Biotically, the primary methylators of mercury are sulfate-reducing and iron-reducing bacteria. Three mechanisms have been proposed for the biotic methylation of mercury by sulfate-reducing bacteria. Mercury methylation can be problematic as methylmercury is toxic and can be bio-magnified through the food web.
Chemistry.
Chemical elements on Earth cycle through atmospheric, terrestrial, and aquatic environments in a process called biogeochemical cycling. Mercury goes through its own version of biogeochemical cycling named the mercury cycle where it circulates through the environment and changes between oxidation states: Hg(0), Hg(I), Hg(II). When mercury is present in the environment microbial organisms can uptake the elemental form of mercury. This signals the transcription of the genes "hgcA" and "hgcB" are transcribed to synthesize the HgcA and HgcB proteins. These proteins can then start the methylation reaction to form methylmercury.
Biochemical.
Microbial.
Species from all three domains of life have been found to play a role in the methylation of mercury. More species have been discovered that genetically are capable of mercury methylation due to the discovery of the "hgcAB" genes. It is not known if the HgcA and HgcB proteins create a multienzyme complex or work sequentially. It has also been shown that deletion of either gene results in the complete loss of the ability to methylate mercury.
Bacterial species currently known to methylate mercury include the major of "Desulfovibrio spp." (i.e. Desulfovibrio desulfuricans). and "Geobacter spp." (i.e. "Geobacter sulfurreducens") Other species with the "hgcAB" genes that suspected to produce MeHg include "Bacteroidetes", "Chloroflexi", "Nitrospirae".
Archaeal species known to methylate mercury include the majority of species of methanogen class "Methanomicrobia", however, class "Thermoplasmata" has been found to carry the "hgcAB" genes. No other species of methanogens have been found with the ability of mercury methylation.
Reactions.
pH influences on mercury methylation can be variable depending on the species that are undergoing the reactions. Some findings demonstrate that an increase in the hydrogen ion concentration resulted in large increases of the Hg(II) uptake, leading to potential impacts on the actual methylation of mercury. Another finding demonstrated that the decrease in pH leads to a shift in the production of methyl mercury species. Specifically, the production of dimethylmercury decreases and the production of monomethylmercury increases, but total remains essentially constant.
Enough adequate studies on the temperature influences on the methylation of mercury have not been published. Mercury methylation reaches maximum activity in the summer but this enhanced methylation may be due to other factors unrelated to temperature. However, it is evident that temperature affects microbial activity which will correspond to an impact on the subsequent biochemical reactions that lead to methylation of mercury.
Similar to the pH effects, different concentrations of available mercury ion lead to different products and complexes of mercury being produced. In addition, the enzymes HgcA and HgcB have a very low Km and will therefore readily bind to the available mercury even at very low concentrations.
Transport into cell.
Before mercury can be methylated, it must be transported into the cell through the lipid membrane. Mercury ions are bound by a mercury scavenger protein, MerP. MerP transfers the mercury ion to a cytoplasmic membrane transporter, MerT, then to the active site of mercuric reductase or mercury(II) reductase in the cytoplasm.
Normally mercury would be toxic to the cell, but some microorganisms are resistant to mercury ion due to an inducible "mer" operon. Translation of the operon results in the synthesis of mercuric reductase. Mercuric reductase will reduce the mercury ion into elemental mercury, which is volatilized from the cell. If mercuric reductase is not employed, methylation of mercury can occur via three identified pathways.
Biochemical pathway.
Cultures of sulfate reducing bacteria grown without the presence of sulfate will not methylate mercury. It is a possibility that the respiration of these cells is coupled to mercury methylation.
The "Acetyl-CoA pathway" for mercury methylation is done by sulfate reducing bacteria and is catalyzed by a corrinoid dependent protein. Through this pathway, the methyl group is proposed to originate from C-3 serine. A transfer of the methyl group from CH3-Tetrahydrofolate to the corrinoid protein requires the genes "hgcA" and "hgcB" . The methyl group now on the corrinoid protein will then be transferred to mercury ion.
This activity was shown to decrease in aerobic environments, suggesting that the methylation occurs anaerobically.
Acetate Metabolic pathway (methyl-transferase enzymes) is very similar to the acetyl CoA pathway, where methyltransferase enzymes involving tetrahydrofolate intermediates are utilized.
It was shown that methylation of mercury was greater by three orders of magnitude in cells that were capable of utilizing acetate.
Methylation of mercury can also occur using a cobalamin dependent "methionine synthase". The cobalamin dependent process requires the use of the substrate S-adenosylmethionine, a biological methylating agent.
As methionine synthase was used, it is possible that the enzyme that methylates mercury is also able to transfer methyl groups from CH3-Tetrahydrofolate to thiols.
Environmental impact.
Animal health.
Methyl mercury is a toxic substance to living organisms. The toxicity of methylmercury in humans is due to methyl mercury crossing the blood-brain barrier and causing cell lysis in the central nervous system. The cell damage is irreversible. The half-life of methylmercury in human tissue is 70 days, which allows it ample time to accumulate to toxic levels. Humans are exposed to methyl mercury from the consumption of aquatic species. As mercury bioaccumulates through the food chain, the amount of methyl mercury increases to these toxic levels.


Phenyl(trichloromethyl)mercury

Phenyl(trichloromethyl)mercury is an organomercury compound with the formula C6H5HgCCl3. It is a white solid that is soluble in organic solvents. The compound is used as a source of dichlorocarbene, e.g. in cyclopropanation reactions, illustrated with tetrachloroethylene as a substrate, the product being hexachlorocyclopropane:
The compound is prepared by treating phenylmercuric chloride with sources of dichlorocarbene. These include the base/haloform reaction and thermolysis of sodium trichloroacetate:
Related compounds.
Closely related compounds include phenyl(bromodichloromethyl)mercury (CAS registry number 3294-58-4) and phenyl(tribromomethyl)mercury (CAS registry number 3294-60-8). According to X-ray crystallography, the former has nearly linear coordination geometry at mercury, with a C-Hg-C angle of 179° and Hg-C distances of 2.047 Å.
Also known is bis(trichloromethyl)mercury, Hg(CCl3)2.


Methyl hypochlorite

Methyl hypochlorite is the simplest of the organic alkyl hypochlorites. It is an unstable compound that can be produced by the reaction of methanol with hypochlorous acid. It was first synthesized by Sandmeyer in the 1880s.
Methyl hypochlorite forms in the Earth's atmosphere by a reaction between ClO and CH3OO and is thought to be an important species in ozone destruction over the Arctic and Antarctic regions.


Dechlorane plus

Dechlorane plus (abbrev. "DDC-CO") is a polychlorinated flame retardant produced by Oxychem. Its log P is 11.27±0.94. It is produced by the Diels-Alder reaction of two equivalents of hexachlorocyclopentadiene with one equivalent of cyclooctadiene. The "syn" and "anti" isomer are formed in the approximate ratio of 1:3.
Dechlorane plus was first found in the environment in 2006 in air around the Great Lakes. Since then, its environmental occurrence has been further documented in several studies including sediments of the Great Lakes; zooplankton, fish, and mussels in Lake Winnipeg and Lake Ontario; air and seawater from the Arctic to Antarctica; and Chinese air. Modeling data indicates that Dechlorane Plus may be persistent, bioaccumulative, and subject to long-range transport and that it may be candidates for Annex D evaluation under the United Nations Stockholm Convention on Persistent Organic Pollutants.
Dechlorane plus was added to the list of REACH Substances of Very High Concern on January 15, 2018.


Polythionates

Polythionates are oxoanions with the formula S"n"(SO3)22- ("n"≥0). They occur naturally and are the products of redox reactions of thiosulfate. Polythionates are readily isolable, unlike the parent polythionic acids.
Preparation.
Many members of the polythionates have been characterized: dithionate, trithionate, tetrathionate, pentathionate, etc.
These salts are often generated by oxidation of thiosulfate. For example, tetrathionate is obtained by oxidation of thiosulfate ion with iodine (reaction is used in iodometry):
More specialized routes involve reactions of sulfur chlorides with bisulfite salts:
Potassium pentathionate ion has been obtained from SCl2, sodium thiosulfate, and potassium acetate. Initially prismatic crystals of potassium tetrathionate appear, then lamellar crystals of potassium pentathionate, from which the influence of tartaric acid makes an aqueous solution of pentathionic acid.
Potassium hexathionate K2S6O6 has been synthesized by combining KNO2 and K2S2O3 in concentrated HCl at low temperatures.


Confederate Monument of Bardstown

The Confederate Monument of Bardstown, in Bardstown, Kentucky was erected in 1903 in the Bardstown/St. Joseph's Cemetery to honor the sacrifice of 67 Confederate soldiers who died during the American Civil War, 17 of which are unknown. Most were under the command of Major General Braxton Bragg who died in 1862 in conflicts around Bardstown. It was dedicated by the J. Crepps Wickliffe Chapter of the United Daughters of the Confederacy. The base is made of limestone, and the statue of the Confederate soldier was made of zinc. A relief portrait of General Robert E. Lee is located directly beneath the statue.
The inscription reads:
 Lord God of hosts, Be with us yet;
 Lest we forget, Lest we forget.
 Marble tells not of their valor's worth,
 Nameless, they rest in quiet earth.
 We care not whence they came,
 Dear is their lifeless clay;
 Whether unknown, or known to fame,
 their cause and country still the same,
 they died and wore the gray."
It was placed on the National Register of Historic Places on July 17, 1997, one of sixty monuments to the American Civil War in Kentucky so honored on the same day. Starting in early autumn of 1999 the Sons of Confederate Veterans endeavored to restore/erect the individual gravemarkers.


Europium(III) nitrate

Europium(III) nitrate is an inorganic compound with the formula Eu(NO3)3. Its hexahydrate is the most common form, which is a colorless hygroscopic crystal.
Preparation.
Dissolving europium(III) oxide (Eu2O3) in dilute nitric acid produces europium(III) nitrate.
Complexes.
Europium(III) nitrate reacts with some ligands to form complexes. It reacts with 1,3,5-trimesic acid, producing europium metal-organic framework, a coordination polymer, under hydrothermal conditions.


Nickel(II) phosphate

Nickel(II) phosphate is an inorganic compound with the formula Ni3(PO4)2. It is a mint green paramagnetic solid that is insoluble in water.
Hydrated nickel(II) phosphate.
The hydrate Ni3(PO4)2·8(H2O) is a light green solid, which can be prepared by hydrothermal synthesis and also occurs as the mineral arupite. It features octahedral Ni centers, which are bound to water and phosphate.


Selenium oxybromide

Selenium oxybromide (SeOBr2) is a selenium oxohalide chemical compound.
Preparation.
Selenium oxybromide can be prepared through the reaction of selenium dioxide and selenium tetrabromide. Selenium and selenium dioxide are reacted with bromine to form selenium monobromide and selenium tetrabromide. Dissolving the selenium dioxide in the tetrabromide will produce the oxybromide.
Properties.
Selenium oxybromide is a reddish-brown solid with a low melting point (41.6 °C) and chemical properties similar to selenium oxychloride. It boils at 220 °C and decomposes near the boiling point, making distillation an ineffective purification method. Its electrical conductivity in the liquid state just above the melting temperature is 6×10−5 S/m. SeOBr2 is hydrolyzed by water to form H2SeO3 and HBr.
SeOBr2 is highly reactive, with most reactions taking place in the liquid state. Selenium will dissolve in it, forming Se2Br2. Iron, copper, gold, platinum, and zinc are all attacked by SeOBr2.


Organoboron chemistry

Organoborane or organoboron compounds are chemical compounds of boron and carbon that are organic derivatives of BH3, for example trialkyl boranes. Organoboron chemistry or organoborane chemistry is the chemistry of these compounds.
Organoboron compounds are important reagents in organic chemistry enabling many chemical transformations, the most important one called hydroboration. Reactions of organoborates and boranes involve the transfer of a nucleophilic group attached to boron to an electrophilic center either inter- or intramolecularly. α,β-Usaturated borates, as well as borates with a leaving group at the α position, are highly susceptible to intramolecular 1,2-migration of a group from boron to the electrophilic α position. Oxidation or protonolysis of the resulting organoboranes may generate a variety of organic products, including alcohols, carbonyl compounds, alkenes, and halides.
Properties of the B-C bond.
The C-B bond has low polarity (the difference in electronegativity 2.55 for carbon and 2.04 for boron), and therefore alkyl boron compounds are in general stable though easily oxidized.
In part because its lower electronegativity, boron often forms electron-deficient compounds, such as the triorganoboranes. Vinyl groups and aryl groups donate electrons and make boron less electrophilic and the C-B bond gains some double bond character. Like the parent borane, diborane, organoboranes are classified in organic chemistry as strong electrophiles because boron is unable to gain a full octet of electrons. Unlike diborane however, most organoboranes do not form dimers.
Synthesis.
From Grignard reagents.
Simple organoboranes such as triethylborane or tris(pentafluorophenyl)boron can be prepared from trifluoroborane (as the ether complex) and the ethyl or pentafluorophenyl Grignard reagent. The borates (R4B−) are generated via addition of R−-equivalents (RMgX, RLi, etc.) to R3B.
From alkenes.
Alkenes insert into B-H bonds of boranes in a process called hydroboration. The process involves anti-Markovnikov addition. Hydroboration of alkenes or alkynes with borane (BH3) or borane equivalents leads to the conversion of only 33% of the starting olefin to product after oxidation or protonolysis—the remaining olefin is incorporated into boron-containing byproducts. One organoboron reagent that is often employed in synthesis is 9-BBN. Hydroborations take place stereospecifically in a "syn" mode, that is on the same face of the alkene. In this concerted reaction the transition state is represented as a square with the corners occupied by carbon, carbon, hydrogen and boron with maximum overlap between the two olefin p-orbitals and the empty boron orbital.
By borylation.
Metal-catalyzed C-H Borylation reactions are transition metal catalyzed organic reactions that produce an organoboron compound through functionalization of aliphatic and aromatic C-H bonds. A common reagent in this type of reaction is bis(pinacolato)diboron.
Classes of organoboron compounds.
Organoboranes and hydrides.
Among the most studied classes of organoboron compounds have the formula BRnH3−n. As discussed above, these compounds are used as catalysts, reagents, and synthetic intermediates. The trialkyl and triaryl derivatives feature trigonal planar boron center that is typically only weakly Lewis acidic. Except for a few very bulky derivatives, the hydrides (BRnH3−n for n = 1 or 2) exist as dimers, reminiscent of the structure of diborane itself. Trisubstituted derivatives, e.g. triethylboron are monomers.
Borinic and boronic acids and esters (BRn(OR)3-n).
Compounds of the type BRn(OR)3-n are called borinic esters (n = 2), boronic esters (n = 1), and borates (n = 0). Boronic acids are used in Suzuki reaction. Trimethyl borate, which is debatably not an organoboron compound, is an intermediate in the production of sodium borohydride.
Boron clusters.
Boron is renowned for forming cluster compounds, e.g. dodecaborate [B12H12]2-. Many organic derivatives are known for such clusters. One example is [B12(CH3)12]2- and its radical derivative [B12(CH3)12]−. Related cluster compounds with carbon vertices are called carboranes. The best known is orthocarborane, with the formula C2B10H12. Although they have few commercial applications, carboranes have attracted much attention because they are so structurally unusual. Anionic derivatives, dicarbollides, e.g., [C2B9H11]2− are ligands that behave like cyclopentadienide.
Bora-substituted aromatic compounds.
In borabenzene, one CH center in benzene is replaced by boron. These compounds are invariably isolated as adducts, e.g., C5H5B-pyridine. The cyclic compound borole, a structural analog of pyrrole, has not been isolated, but substituted derivatives known as boroles are known. The cyclic compound borepin is aromatic.
Boryl compounds.
Boryl anions have the formula R2B−. Nucleophilic anionic boryl compounds have long been elusive but a 2006 study described a boryllithium compound, which reacts as a nucleophile: Organometallic compounds with metal to boron bonds, (i.e., M–BR2), are known as boryl complexes. Related ligands are borylenes (M–B(R)–M).
The absence of lithium boryl compounds is notable because in other period 2 elements lithium salts are common e.g. lithium fluoride, lithium hydroxide, lithium amide, and methyllithium. The gap highlights the very low electronegativity of boron. Reaction of base with a borohydride R2BH does not result in deprotonation to the boryl anion R2B− but to formation of the boryl anion R2B−H(base)+. This reaction product has a complete octet. Instead the boryl compound is prepared by reductive heterolysis of a boron-bromide bond by lithium metal. The new boryl lithium compound is very similar to and isoelectronic with N-heterocyclic carbenes. It is designed to benefit from aromatic stabilization (6-electron system counting the nitrogen lone pairs and an empty boron p-orbital, see structure A) and from kinetic stabilization from the bulky 2,6-diisopropylphenyl groups. X-ray diffraction confirms sp2 hybridization at boron and its nucleophilic addition reaction with benzaldehyde gives further proof of the proposed structure.
Alkylideneboranes.
Alkylideneboranes of the type RB=CRR with a boron – carbon double bond are rarely encountered. An example is borabenzene. The parent compound is HB=CH2 which can be detected at low temperatures. A fairly stable derivative is CH3B=C(SiMe3)2 but is prone to cyclodimerisation.
NHC adducts of boron.
NHCs and boranes form stable NHC borane adducts. Triethylborane adducts can be synthesised directly from the imidazolium salt and lithium triethylborohydride. Members of this compound class are investigated for use as reagent or catalyst.
Diborenes.
Chemical compounds with boron to boron double bonds are rare. In 2007 the first neutral diborene (RHB=BHR) was presented by Gregory Robinson of the University of Georgia. Each boron atom has a proton attached to it and each boron atom is coordinated to a NHC carbene. The parent structure with the additional carbene ligands is diborane(2).
A reported diboryne is based on similar chemistry.
Reactions.
Organoboranes (R3B) and borates (R4B−, generated via addition of R− to R3B) possess boron–carbon bonds that are polarized toward carbon. Thus, the carbon attached to boron is nucleophilic, and in borates this property may be harnessed to transfer one of the R groups to an electrophilic center either inter- or (more often) intramolecularly. In the latter case, the nucleophilic R group is able to undergo 1,2-migration towards an electrophilic carbon attached to boron. The resulting reorganized borane can then be oxidized or subjected to protonolysis to afford organic products. Examples covered in this article are shown below.
Hydroboration of alkenes or alkynes is an efficient method for the generation of boranes; however, the use of borane (BH3) or borane equivalents leads to the conversion of only 33% of the starting olefin to product after oxidation or protonolysis—the remaining olefin is incorporated into boron-containing byproducts. The use of a stoichiometric amount of 9-borabicyclo[3.3.1]nonane (9-BBN) as the hydroborating reagent provides a solution to this problem.
Hydroboration-oxidation.
In organic synthesis the hydroboration reaction is taken further to generate other functional groups in the place of the boron group. The hydroboration-oxidation reaction offers a route to alcohols by oxidation of the borane with hydrogen peroxide or to the carbonyl group with the stronger oxidizing agent chromium oxide.
Rearrangements.
Carbon monoxide is found to react with trialkylboranes. What follows is a 1,2-rearrangement whereby an alkyl substituent migrates from boron to the carbon of the carbonyl group. Homologated primary alcohols result from the treatment of organoboranes with carbon monoxide and a hydride.
Allylboration.
Asymmetric allylboration demonstrates another useful application of organoboranes in carbon–carbon bond formation. In this example from Nicolaou's synthesis of the epothilones, asymmetric allylboration (using an allylborane derived from chiral alpha-pinene) is used in conjunction with TBS protection and ozonolysis. Overall, this provides a two-carbon homologation sequence that delivers the required acetogenin sequence.
As reducing agent.
Borane hydrides such as 9-BBN and L-selectride (lithium tri-sec-butylborohydride) are reducing agents. An example of an asymmetric catalyst for carbonyl reductions is the CBS catalyst. This catalyst is also based on boron, the purpose of which is coordination to the carbonyl oxygen atom.
Borates.
Trialkylboranes, BR3, can be oxidized to the corresponding borates, B(OR)3. One method for the determination of the amount of C-B bonds in a compound is by oxidation of R3B with trimethylamine oxide (Me3NO) to B(OR)3. The trimethylamine (Me3N) formed can then be titrated.
Boronic acids RB(OH)2 react with potassium bifluoride K[HF2] to form trifluoroborate salts K[RBF3] which are precursors to nucleophilic alkyl and aryl boron difluorides, ArBF2. The salts are more stable than the boronic acids themselves and used for instance in alkylation of certain aldehydes:
Suzuki reaction and related reactions.
Organoboron compounds also lend themselves to transmetalation reactions, especially with organopalladium compounds. This reaction type is exemplified in the Suzuki reaction, which involves coupling of aryl- or vinyl-boronic acid with an aryl- or vinyl-halide catalyzed by a palladium(0) complex,
][\text{Base}] R1-R2}\\
This reaction is an important method for making carbon-carbon bonds.
Mechanism and stereochemistry.
Boranes alone are generally not nucleophilic enough to transfer an alkyl group to an electrophilic center. However, after nucleophilic attack, the resulting borate is highly nucleophilic. If the nucleophile contains unsaturated functionality or a leaving group at the α position, one of the R groups attached to boron is able to migrate to the electrophilic α carbon (see equation (2) below). The propensity of an organic group to migrate depends on its ability to stabilize negative charge: alkynyl > aryl ≈ alkenyl > primary alkyl > secondary alkyl > tertiary alkyl. Migration takes place with retention of configuration at the migrating carbon and inversion of configuration at the migration terminus (provided it is sp3 hybridized). Bis(norbornyl)borane and 9-BBN are often used as "dummy" hydroboration reagents for this reason—only the R group derived from the hydroborated olefin is likely to migrate upon nucleophilic activation.
α-Halo enolates are commonly used as nucleophiles in this context. After nucleophilic attack at boron, the resulting ketoboronate rearranges to a neutral enolborane. Upon protonolysis, a functionalized carbonyl compound results. The intermediate enolboranes may also be quenched with electrophiles.
Alkynylboronates are versatile intermediates that can be converted to either ketones or olefins after simultaneous migration and attack of the alkyne on a separate electrophile. The electrophile and migrating group end up "trans" in the resulting alkenylborane. Protonolysis of this intermediate generates olefins, while oxidation leads to ketones after tautomerization.
Scope and limitations of reactions.
The scope of organoboranes and borates as reagents for organic synthesis is extremely wide. Reactions of organoboron compounds may produce alcohols, carbonyl compounds, halides, peroxides, amines, and other functionality depending on other starting materials employed and reaction conditions. This section covers a small subset of these methods, focusing on the synthesis of alcohols, carbonyl compounds, and halides.
Alcohol synthesis from organoboranes and borates relies on either nucleophilic group transfer to a carbonyl group or oxidation of an intermediate organoborane. Homologated primary alcohols result from the treatment of organoboranes with carbon monoxide and a hydride.
Tertiary alcohols with two identical groups attached to the alcohol carbon may be synthesized through a double migration reaction of alkynylborates in the presence of acid. Use of a single equivalent of acid and oxidation or protonolysis leads to ketones or olefins, respectively (see Mechanism and Stereochemistry section above).
Acylation of borates is possible in the presence of an acyl halide. Here, the borate was generated from tri(cyclopentyl)borane and phenyllithium; the three cyclopentyl groups are serving as "dummy" groups and do not migrate to a significant amount.
Treatment of trialkylboranes with α-halo enolates leads to functionalized ketones. Because the migration is stereospecific (retentive with respect to the migrating group and invertive at the α carbon), this method provides a means for the synthesis of enantiopure α-alkyl or -aryl ketones.
α-Halo ester enolates also add to boranes to eventually afford α-functionalized products; however, yields are slightly lower. Diazoesters and diazoketones may also be used in this context without the requirement for external base. α,α'-Dialo enolates react with boranes to form α-halo carbonyl compounds that can be further functionalized at the α position.
Halides may be synthesized from organoboranes by activating with hydroxide or alkoxide and treatment with X2. Two of the three alkyl groups attached to the borane may be converted to halide in the presence of excess base, but the use of disiamylborane as the hydroborating reagent permits the selective halogenation of only the hydroborated olefin.
Treatment of an alkenylborane with iodine or bromine leads to migration of one of the organic groups attached to boron. Alkynyl groups migrate selectively, forming enynes after treatment with sodium acetate and hydrogen peroxide.
Other uses.
TEB – Triethylborane was used to ignite the JP-7 fuel of the Pratt & Whitney J58 variable cycle engines powering the Lockheed SR-71 Blackbird.


Potassium fluoride

Potassium fluoride is the chemical compound with the formula KF. After hydrogen fluoride, KF is the primary source of the fluoride ion for applications in manufacturing and in chemistry. It is an alkali halide and occurs naturally as the rare mineral carobbiite. Solutions of KF will etch glass due to the formation of soluble fluorosilicates, although HF is more effective.
Preparation.
Potassium fluoride is prepared by dissolving potassium carbonate in hydrofluoric acid. Evaporation of the solution forms crystals of potassium bifluoride. The bifluoride on heating yields potassium fluoride:
Platinum or heat resistant plastic containers are often used for these operations.
Potassium chloride converts to KF upon treatment with hydrogen fluoride. In this way, potassium fluoride is recyclable.
Crystalline properties.
KF crystallizes in the cubic NaCl crystal structure. The lattice parameter at room temperature is 0.266 nm.
Applications in organic chemistry.
In organic chemistry, KF can be used for the conversion of chlorocarbons into fluorocarbons, via the Finkelstein (alkyl halides) and Halex reactions (aryl chlorides). Such reactions usually employ polar solvents such as dimethyl formamide, ethylene glycol, and dimethyl sulfoxide. More efficient fluorination of aliphatic halides can be achieved with a combination of crown ether and bulky diols in acetonitrile solvent.
Safety considerations.
Like other sources of the fluoride ion, F−, KF is poisonous, although lethal doses approach gram levels for humans. It is harmful by inhalation and ingestion. It is highly corrosive, and skin contact may cause severe burns.


Sodium nitride

Sodium nitride is the inorganic compound with the chemical formula Na3N. In contrast to lithium nitride and some other nitrides, sodium nitride is an extremely unstable alkali metal nitride. It can be generated by combining atomic beams of sodium and nitrogen deposited onto a low-temperature sapphire substrate.
It readily decomposes into its elements:
Synthesis.
Sodium nitride can be synthesized in two different ways: by the thermal decomposition of NaNH2 or by the direct reaction of the elements. The most common way to successfully synthesize sodium nitride has been done by Dieter Fischer & Martin Jansen and Grigori Vajenine using the latter method. The first way is to introduce desired ratios of Na and N2 in gas phase separately and depositing them in a vacuum chamber on a cooled substrate, which is then heated to room temperate (298 K) to crystallize.
The second method is to react elemental sodium with plasma activated nitrogen on a metal surface. This synthesis can be further facilitated by introducing liquid Na-K alloy to the compound with the excess liquid removed and washed with fresh alloy. The solid is then separated from the liquid using a centrifuge. However Vajenine’s method is very air-sensitive and can decompose and combust rapidly, unless exposed to a pure oxygen (O2) environment.
Characteristics.
Sodium nitride can be of reddish brown or dark blue color depending on the synthesis of the compound due to intrinsic properties. It shows no signs of decomposition after several weeks when at room temperature. The compound does not have a melting point as it decomposes back into its elemental forms as demonstrated using mass spectrometry around 360 K. The estimated enthalpy of formation for the compound is +64 kJ/mol.
Structure.
Sodium nitride seems to be about 90% ionic at room temperature, but has the band gap typical for a semiconductor. It adopts the anti-ReO3 structure with a simple lattice made up of NNa6 octahedra. The compound has N−Na bond lengths of 236.6 pm. This structure has been confirmed through X-ray diffraction and more recently neutron diffraction on powder and single crystals.


Ammonium pertechnetate

Ammonium pertechnetate is a chemical compound with the formula NH4TcO4. It is the ammonium salt of pertechnetic acid. The most common form uses 99Tc. The compound is readily soluble in aqueous solutions forming ammonium and pertechnetate ions.
It can be synthesized by the reaction of pertechnetic acid and ammonium nitrate:
It thermally decomposes under inert atmosphere at 700 °C to technetium dioxide:


Hydrate

In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understood.
Chemical nature.
Inorganic chemistry.
Hydrates are inorganic salts "containing water molecules combined in a definite ratio as an integral part of the crystal" that are either bound to a metal center or that have crystallized with the metal complex. Such hydrates are also said to contain "water of crystallization" or "water of hydration". If the water is heavy water, where the hydrogen involved is the isotope deuterium, then the term "deuterate" may be used in place of "hydrate".
A colorful example is cobalt(II) chloride, which turns from blue to red upon hydration, and can therefore be used as a water indicator.
The notation ""hydrated compound"⋅"n"H2O", where "n" is the number of water molecules per formula unit of the salt, is commonly used to show that a salt is hydrated. The "n" is usually a low integer, though it is possible for fractional values to occur. For example, in a monohydrate "n" = 1, and in a hexahydrate "n" = 6. Numerical prefixes of Greek origin are:
A hydrate that has lost water is referred to as an anhydride; the remaining water, if any exists, can only be removed with very strong heating. A substance that does not contain any water is referred to as anhydrous. Some anhydrous compounds are hydrated so easily that they are said to be hygroscopic and are used as drying agents or desiccants.
Organic chemistry.
In organic chemistry, a hydrate is a compound formed by the hydration, i.e. "Addition of water or of the elements of water (i.e. H and OH) to a molecular entity". For example: ethanol, CH3−CH2−OH, is the product of the hydration reaction of ethene, CH2=CH2, formed by the addition of H to one C and OH to the other C, and so can be considered as the hydrate of ethene. A molecule of water may be eliminated, for example, by the action of sulfuric acid. Another example is chloral hydrate, CCl3−CH(OH)2, which can be formed by reaction of water with chloral, CCl3−CH=O.
Many organic molecules, as well as inorganic molecules, form crystals that incorporate water into the crystalline structure without chemical alteration of the organic molecule (water of crystallization). The sugar trehalose, for example, exists in both an anhydrous form (melting point 203 °C) and as a dihydrate (melting point 97 °C). Protein crystals commonly have as much as 50% water content.
Molecules are also labeled as hydrates for historical reasons not covered above. Glucose, C6H12O6, was originally thought of as C6(H2O)6 and described as a carbohydrate.
Hydrate formation is common for active ingredients. Many manufacturing processes provide an opportunity for hydrates to form and the state of hydration can be changed with environmental humidity and time. The state of hydration of an active pharmaceutical ingredient can significantly affect the solubility and dissolution rate and therefore its bioavailability.
Clathrate hydrates.
Clathrate hydrates (also known as gas hydrates, gas clathrates, etc.) are water ice with gas molecules trapped within; they are a form of clathrate. An important example is methane hydrate (also known as gas hydrate, methane clathrate, etc.).
Nonpolar molecules such as methane can form clathrate hydrates with water, especially under high pressure. Although there is no hydrogen bonding between water and guest molecules when methane is the guest molecule of the clathrate, guest–host hydrogen bonding often forms when the guest is a larger organic molecule such as tetrahydrofuran. In such cases the guest–host hydrogen bonds result in the formation of L-type Bjerrum defects in the clathrate lattice.
Stability.
The stability of hydrates is generally determined by the nature of the compounds, their temperature, and the relative humidity (if they are exposed to air).


Plagioclase

Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more properly known as the plagioclase feldspar series. This was first shown by the German mineralogist Johann Friedrich Christian Hessel (1796–1872) in 1826. The series ranges from albite to anorthite endmembers (with respective compositions NaAlSi3O8 to CaAl2Si2O8), where sodium and calcium atoms can substitute for each other in the mineral's crystal lattice structure. Plagioclase in hand samples is often identified by its polysynthetic crystal twinning or 'record-groove' effect.
Plagioclase is a major constituent mineral in the Earth's crust, and is consequently an important diagnostic tool in petrology for identifying the composition, origin and evolution of igneous rocks. Plagioclase is also a major constituent of rock in the highlands of the Earth's moon. Analysis of thermal emission spectra from the surface of Mars suggests that plagioclase is the most abundant mineral in the crust of Mars.
Its name comes from Ancient Greek (, "oblique") + (, "fracture"), in reference to its two cleavage angles.
Plagioclase series members.
The composition of a plagioclase feldspar is typically denoted by its overall fraction of anorthite (%An) or albite (%Ab), and readily determined by measuring the plagioclase crystal's refractive index in crushed grain mounts, or its "extinction angle" in thin section under a polarizing microscope. The extinction angle is an optical characteristic and varies with the albite fraction (%Ab). There are several named plagioclase feldspars that fall between albite and anorthite in the series. The following table shows their compositions in terms of constituent anorthite and albite percentages.
Intermediate members.
The intermediate members of the plagioclase group are very similar to each other and normally cannot be distinguished except by their optical properties. The specific gravity in each member (albite 2.62) increases 0.02 per 10% increase in anorthite (2.75).


Cobalt(III) oxide

Cobalt (III) oxide is the inorganic compound with the formula of Co2O3. Although only two oxides of cobalt are well characterized, CoO and Co3O4, procedures claiming to give Co2O3 have been described. Thus treatment of Co(II) salts such as cobalt(II) nitrate with an aqueous solution of sodium hypochlorite (also known as bleach) gives a black solid. Some formulations of the catalyst hopcalite contain "Co2O3".


Fullerene chemistry

Fullerene chemistry is a field of organic chemistry devoted to the chemical properties of fullerenes. Research in this field is driven by the need to functionalize fullerenes and tune their properties. For example, fullerene is notoriously insoluble and adding a suitable group can enhance solubility. By adding a polymerizable group, a fullerene polymer can be obtained. Functionalized fullerenes are divided into two classes: exohedral fullerenes with substituents outside the cage and endohedral fullerenes with trapped molecules inside the cage.
This article covers the chemistry of these so-called "buckyballs," while the chemistry of carbon nanotubes is covered in carbon nanotube chemistry.
Chemical properties of fullerenes.
Fullerene or C60 is soccer-ball-shaped or "Ih" with 12 pentagons and 20 hexagons. According to Euler's theorem these 12 pentagons are required for closure of the carbon network consisting of "n" hexagons and C60 is the first stable fullerene because it is the smallest possible to obey this rule. In this structure none of the pentagons make contact with each other. Both C60 and its relative C70 obey this so-called isolated pentagon rule (IPR). The next homologue C84 has 24 IPR isomers of which several are isolated and another 51,568 non-IPR isomers. Non-IPR fullerenes have thus far only been isolated as endohedral fullerenes such as Tb3N@C84 with two fused pentagons at the apex of an egg-shaped cage. or as fullerenes with exohedral stabilization such as C50Cl10 and reportedly C60H8. Fullerenes with less than 60 carbons do not obey isolated pentagon rule (IPR).
Because of the molecule's spherical shape the carbon atoms are highly pyramidalized, which has far-reaching consequences for reactivity. It is estimated that strain energy constitutes 80% of the heat of formation. The conjugated carbon atoms respond to deviation from planarity by orbital rehybridization of the sp² orbitals and π orbitals to a sp2.27 orbital with a gain in p-character. The p lobes extend further outside the surface than they do into the interior of the sphere and this is one of the reasons a fullerene is electronegative. The other reason is that the empty low-lying π* orbitals also have a high s character.
The double bonds in fullerene are not all the same. Two groups can be identified: 30 so-called [6,6] double bonds connect two hexagons and 60 [5,6] bonds connect a hexagon and a pentagon. Of the two the [6,6] bonds are shorter with more double-bond character and therefore a hexagon is often represented as a cyclohexatriene and a pentagon as a pentalene or [5]radialene. In other words, although the carbon atoms in fullerene are all conjugated the superstructure is not a super aromatic compound. The X-ray diffraction bond length values are 139.1 pm for the [6,6] bond and 145.5 pm for the [5,6] bond.
C60 fullerene has 60 π electrons but a closed shell configuration requires 72 electrons. The fullerene is able to acquire the missing electrons by reaction with potassium to form first the salt and then the In this compound the bond length alternation observed in the parent molecule has vanished.
Fullerene reactions.
Fullerenes tend to react as electrophiles. An additional driving force is relief of strain when double bonds become saturated. Key in this type of reaction is the level of functionalization i.e. monoaddition or multiple additions and in case of multiple additions their topological relationships (new substituents huddled together or evenly spaced). In conformity with IUPAC rules, the terms methanofullerene are used to indicate the ring-closed (cyclopropane) fullerene derivatives, and fulleroid to ring-open (methanoannulene) structures.
Nucleophilic additions.
Fullerenes react as electrophiles with a host of nucleophiles in nucleophilic additions. The intermediary formed carbanion is captured by another electrophile. Examples of nucleophiles are Grignard reagents and organolithium reagents. For example, the reaction of C60 with methylmagnesium chloride stops quantitatively at the penta-adduct with the methyl groups centered around a cyclopentadienyl anion which is subsequently protonated. Another nucleophilic reaction is the Bingel reaction.
Fullerene reacts with chlorobenzene and aluminium chloride in a Friedel-Crafts alkylation type reaction. In this hydroarylation the reaction product is the 1,2-addition adduct (Ar-CC-H).
Pericyclic reactions.
The [6,6] bonds of fullerenes react as dienes or dienophiles in cycloadditions for instance Diels-Alder reactions. 4-membered rings can be obtained by [2+2]cycloadditions for instance with benzyne. An example of a 1,3-dipolar cycloaddition to a 5-membered ring is the Prato reaction.
Hydrogenations.
Fullerenes are easily hydrogenated by several methods. Examples of hydrofullerenes are C60H18 and C60H36. However, completely hydrogenated C60H60 is only hypothetical because of large strain. Highly hydrogenated fullerenes are not stable, as prolonged hydrogenation of fullerenes by direct reaction with hydrogen gas at high temperature conditions results in cage fragmentation. At the final reaction stage this causes collapse of cage structure with formation of polycyclic aromatic hydrocarbons.
Oxidations.
Although more difficult than reduction, oxidation of fullerene is possible for instance with oxygen and osmium tetraoxide.
Hydroxylations.
Fullerenes can be hydroxylated to fullerenols or fullerols. Water solubility depends on the total number of hydroxyl groups that can be attached. One method is fullerene reaction in diluted sulfuric acid and potassium nitrate to C60(OH)15. Another method is reaction in diluted sodium hydroxide catalysed by TBAH adding 24 to 26 hydroxyl groups. Hydroxylation has also been reported using solvent-free NaOH / hydrogen peroxide. C60(OH)8 was prepared using a multistep procedure starting from a mixed peroxide fullerene. The maximum number of hydroxyl groups that can be attached (hydrogen peroxide method) stands at 36–40.
Electrophilic additions.
Fullerenes react in electrophilic additions as well. The reaction with bromine can add up to 24 bromine atoms to the sphere. The record holder for fluorine addition is C60F48. According to in silico predictions the as yet elusive C60F60 may have some of the fluorine atoms in endo positions (pointing inwards) and may resemble a tube more than it does a sphere.
Eliminations.
Protocols have been investigated for removing substituents via eliminations after they have served their purpose. Examples are the retro-Bingel reaction and the retro-Prato reaction.
Carbene additions.
Fullerenes react with carbenes to methanofullerenes. The reaction of fullerene with dichlorocarbene (created by sodium trichloroacetate pyrolysis) was first reported in 1993. A single addition takes place along a [6,6] bond.
Radical additions.
Fullerenes can be considered radical scavengers. With a simple hydrocarbon radical such as the t-butyl radical obtained by thermolysis or photolysis from a suitable precursor the tBuC60 radical is formed that can be studied. The unpaired electron does not delocalize over the entire sphere but takes up positions in the vicinity of the tBu substituent.
Fullerenes as ligands.
Fullerene is a ligand in organometallic chemistry. The [6,6] double bond is electron-deficient and usually forms metallic bonds with η = 2 hapticity. Bonding modes such as η = 5 or η = 6 can be induced by modification of the coordination sphere.
Variants.
Open-cage fullerenes.
A part of fullerene research is devoted to so-called open-cage fullerenes whereby one or more bonds are removed chemically exposing an orifice. In this way it is possible to insert into it small molecules such as hydrogen, helium or lithium. The first such open-cage fullerene was reported in 1995. In endohedral hydrogen fullerenes the opening, hydrogen insertion and closing back up has already been demonstrated.
Heterofullerenes.
In heterofullerenes at least one carbon atom is replaced by another element. Based on spectroscopy, substitutions have been reported with boron (borafullerenes), nitrogen (azafullerenes), oxygen, arsenic, germanium, phosphorus, silicon, iron, copper, nickel, rhodium and iridium.
Reports on isolated heterofullerenes are limited to those based on nitrogen and oxygen.
Fullerene dimers.
The C60 fullerene dimerizes in a formal [2+2] cycloaddition to a C120 bucky dumbbell in the solid state by mechanochemistry (high-speed vibration milling) with potassium cyanide as a catalyst. The trimer has also been reported using 4-aminopyridine as catalyst (4% yield) and observed with scanning tunneling microscopy as a monolayer.
Synthesis.
Multistep fullerene synthesis.
Although the procedure for the synthesis of the C60 fullerene is well established (generation of a large current between two nearby graphite electrodes in an inert atmosphere) a 2002 study described an organic synthesis of the compound starting from simple organic compounds.
In the final step a large polycyclic aromatic hydrocarbon consisting of 13 hexagons and three pentagons was submitted to flash vacuum pyrolysis at 1100 °C and 0.01 Torr. The three carbon chlorine bonds served as free radical incubators and the ball was stitched up in a no-doubt complex series of radical reactions. The chemical yield was low: 0.1 to 1%. A small percentage of fullerenes is formed in any process which involves burning of hydrocarbons, e.g. in candle burning. The yield through a combustion method is often above 1%. The method proposed above does not provide any advantage for synthesis of fullerenes compared to the usual combustion method, and therefore, the organic synthesis of fullerenes remains a challenge for chemistry.
A similar exercise aimed at construction of a C78 cage in 2008 (but leaving out the precursor's halogens) did not result in a sufficient yield but at least the introduction of Stone Wales defects could be ruled out. C60 synthesis through a fluorinated fullerene precursor was reported in 2013
Purification.
Fullerene purification is the process of obtaining a fullerene compound free of contamination. In fullerene production mixtures of C60, C70 and higher homologues are always formed. Fullerene purification is key to fullerene science and determines fullerene prices and the success of practical applications of fullerenes. The first available purification method for C60 fullerene was by HPLC from which small amounts could be generated at large expense.
A practical laboratory-scale method for purification of soot enriched in C60 and C70 starts with extraction in toluene followed by filtration with a paper filter. The solvent is evaporated and the residue (the toluene-soluble soot fraction) redissolved in toluene and subjected to column chromatography. C60 elutes first with a purple color and C70 is next displaying a reddish-brown color.
In nanotube processing the established purification method for removing amorphous carbon and metals is by competitive oxidation (often a sulfuric acid / nitric acid mixture). It is assumed that this oxidation creates oxygen containing groups (hydroxyl, carbonyl, carboxyl) on the nanotube surface which electrostatically stabilize them in water and which can later be utilized in chemical functionalization. One report reveals that the oxygen containing groups in actuality combine with carbon contaminations absorbed to the nanotube wall that can be removed by a simple base wash. Cleaned nanotubes are reported to have reduced D/G ratio indicative of less functionalization, and the absence of oxygen is also apparent from IR spectroscopy and X-ray photoelectron spectroscopy.
Experimental purification strategies.
A recent kilogram-scale fullerene purification strategy was demonstrated by Nagata "et al." In this method C60 was separated from a mixture of C60, C70 and higher fullerene compounds by first adding the amidine compound DBU to a solution of the mixture in 1,2,3-trimethylbenzene. DBU as it turns out only reacts to C70 fullerenes and higher which reaction products separate out and can be removed by filtration. C60 fullerenes do not have any affinity for DBU and are subsequently isolated. Other diamine compounds like DABCO do not share this selectivity.
C60 but not C70 forms a 1:2 inclusion compound with cyclodextrin (CD). A separation method for both fullerenes based on this principle is made possible by anchoring cyclodextrin to colloidal gold particles through a sulfur-sulfur bridge. The Au/CD compound is very stable and soluble in water and selectively extracts C60 from the insoluble mixture after refluxing for several days. The C70 fullerene component is then removed by simple filtration. C60 is driven out from the Au/CD compound by adding adamantol which has a higher affinity for the cyclodextrin cavity. Au/CD is completely recycled when adamantol in turn is driven out by adding ethanol and ethanol removed by evaporation; 50 mg of Au/CD captures 5 mg of C60 fullerene.


Promethium(III) oxide

Promethium(III) oxide is a compound with the formula Pm2O3. It is the most common form of promethium.
Crystal structure.
Promethium oxide exists in three major crystalline forms:
The low-temperature cubic form converts to the monoclinic structure upon heating to 750–800 °C, and this transition can only be reversed by melting the oxide. The transition from the monoclinic to hexagonal form occurs at 1740 °C.


Oosterboschite

Oosterboschite is a rare selenide mineral with the formula (Pd,Cu)7Se5. It crystallises in the orthorhombic crystal system. It has a creamy yellow colour and a Moh's hardness of 5. It is often found as grains with no clear shape. The crystals are opaque and often no bigger than 0.4 mm.
Occurrence.
The mineral was approved by the IMA in 1970, after being discovered in the Musonoi Cu–Co mine, near Kolwezi, Katanga Province, Congo. It was later also discovered at the Copper Hills prospect, East Pilbara, Australia, and at Hope’s Nose, Torquay, Devon, England. It is often found in the oxidation zones of the mines, together with verbeekite, trogtalite, selenian digenite, covellite, gold, and chrisstanleyite. It was named after Robert Oosterbosch, a Belgian mining engineer that was very active in the Katanga region, where the type locality is also located.


In-Methylcyclophane

In-Methylcyclophanes are organic compounds and members of a larger family of cyclophanes. These compounds are used to study how chemical bonds in molecules adapt to strain. In-methylcyclophanes in particular have a methyl group in proximity to a benzene ring. This is only possible when both methyl group and ring are attached to the same rigid scaffold. In one In-methylcyclophane molecule this is accomplished with a triptycene frame.
This particular compound is synthesed starting from anthracene with a methyl group added to each arene ring (1,8,9-trimethylanthracene). A triptycene compound is formed from a reaction of this anthracene compound with an aryne in a Diels-Alder reaction in isoamyl nitrite. In this synthesis the precursor to the reactive aryne is 2-amino-6-methylbenzoic acid. Next the methyl substituents are functionalized with bromine groups by the photochemical reaction with "N"-bromosuccinimide or NBS. The final cyclophane is put together by reaction with 1,3,5-tris(mercaptomethyl)benzene with nucleophilic sulfhydryl groups and electrophilic alkyl bromides in a nucleophilic aliphatic Substitution.
X-ray crystallography of the tri-sulfone derivative of this cyclophane shows that the methyl group located 289.6 picometers from the center of the benzene ring. The carbon-to-carbon bond linking the methyl group to the triptycene frame is actually shortened and measures 147.5 to 149.5 pm. The similar bond in the triptycene precursor is 154 pm. Proton NMR analysis shows a chemical shift of 2.52 ppm for the methyl protons compared to that of 3.16 to 3.85 in the anthracene compound. The reason for this anomaly is that the methyl protons are in line with the aromatic ring current of the benzene ring and are therefore severely shielded, an effect similar to the nucleus-independent chemical shift method of analyzing aromaticity.


Zinc chromate

Zinc chromate, ZnCrO4, is a chemical compound containing the chromate anion, appearing as odorless yellow powder or yellow-green crystals, but, when used for coatings, pigments are often added. It is used industrially in chromate conversion coatings, having been developed by the Ford Motor Company in the 1920s.
Production.
A process known as the Cronak process is used to create zinc chromate for use in industry. This process is done by putting zinc or a zinc plated metal in a solution of sodium dichromate and sulfuric acid for a few seconds. Zinc chromate can also be synthesized by using neutral potassium chromate (K2CrO4) and zinc sulfate (ZnSO4), which forms a precipitate.
K2CrO4 + ZnSO4 → ZnCrO4 + K2SO4
Uses.
Zinc chromate's main use is in industrial painting as a coating over iron or aluminum materials. It was used extensively on aircraft by the US military, especially during the 1930s and 1940s. It is also used in a variety of paint coatings for the aerospace and automotive industries. Its use as a corrosion-resistant agent was applied to aluminium alloy parts first in commercial aircraft, and then in military ones. During the 1940 and 1950s it was typically found as the "paint" in the wheel wells of retractable landing gear on US military aircraft to protect the aluminium from corrosion. This compound was a useful coating because it is an anti-corrosive and anti-rust primer. Since it is highly toxic, it also destroys organic growth on the surface. Zinc chromate is also used in spray paints, artists' paints, pigments in varnishes, and in making linoleum.
When used as a pigment, it is known as Zinc Yellow, Buttercup Yellow or Yellow 36. It is rarely used in art because the pigment degenerates into a brown color. This effect can be seen in Georges Seurat's famous painting "A Sunday Afternoon on the Island of La Grande Jatte". The degradation of zinc yellow in Seurat's painting was thoroughly investigated and these findings were subsequently employed in a digital rejuvenation of the painting.
Zinc chromate putty was used as sealant in addition to two O-rings between sections of the failed solid rocket booster on Space Shuttle Challenger. Blowholes in this putty may have been a minor contributor to its catastrophic loss.
Toxicity.
Recent studies have shown that not only is zinc chromate highly toxic, it is also a carcinogen. Exposure to zinc chromate can cause tissue ulceration and cancer. A study published in the "British Journal of Industrial Medicine" showed a significant correlation between the use of zinc chromate and lead chromate in factories and the number of cases in lung cancer experienced by the workers. Because of its toxicity the use of zinc chromate has greatly diminished in recent years.


Indium(III) nitrate

Indium(III) nitrate is a nitrate salt of indium.
References.
https://pubs.acs.org/doi/pdf/10.1021/ed021p407?rand=xc1saf2j


Ikaite

Ikaite is the mineral name for the hexahydrate of calcium carbonate, CaCO3·6H2O. Ikaite tends to form very steep or spiky pyramidal crystals, often radially arranged, of varied sizes from thumbnail size aggregates to gigantic salient spurs. It is only found in a metastable state and decomposes rapidly by losing most of its water content once removed from near-freezing water. This "melting mineral" is more commonly known through its pseudomorphs.
Distribution.
It is usually considered a rare mineral, but this is likely due to difficulty in preserving samples. It was first discovered in nature by the Danish mineralogist Pauly in the Ikka (then spelt Ika) fjord in southwest Greenland, close to Ivittuut, the locality of the famous cryolite deposit. Here ikaite occurs in truly spectacular towers or columns (up to tall) growing out of the fjord floor towards the surface water, where they are naturally truncated by waves, or unnaturally by the occasional boat. At the Ikka Fjord, it is believed that the ikaite towers are created as the result of a groundwater seep, rich in carbonate and bicarbonate ions, entering the fjord bottom in the form of springs, where it hits the marine fjord waters rich in calcium. Ikaite has also been reported as occurring in high-latitude marine sediments at Bransfield Strait, Antarctica; Sea of Okhotsk, Eastern Siberia, off Sakhalin; and Saanich Inlet, British Columbia, Canada. In addition it has been reported in a deep sea fan off the Congo, and therefore probably has worldwide occurrence. The most recent occurrence has been reported by Dieckmann et al. (2008). They found the mineral ikaite directly precipitated in grain sizes of hundreds of micrometers in sea ice in the Weddell Sea and throughout fast ice off Adélie Land, Antarctica. In addition, ikaite can also form large crystals within sediment that grow to macroscopic size, occasionally with good crystal form. There is strong evidence that some of these marine deposits are associated with cold seeps. Ikaite has also been reported as a cryogenic deposit in caves where it precipitates from freezing carbonate-rich water.
Structure.
Ikaite crystallizes in the monoclinic crystal system in space group C2/c with lattice parameters a~8.87A, b~8.23A, c~11.02A, β~110.2°. The structure of ikaite consists of an ion pair of (Ca2+CO32−)0 surrounded by a cage of hydrogen-bonded water molecules which serve to isolate one ion pair from another.
Stability.
Synthetic ikaite was discovered in the nineteenth century in a study by Pelouze. Ikaite is only thermodynamically stable at moderate pressures, so when found near the Earth's surface is always metastable. Nevertheless, as it appears to be at least moderately common in nature, it is clear that the conditions for metastable nucleation and growth cannot be too restrictive. Cold water is certainly required for formation, and nucleation inhibitors like phosphate ions for the growth of anhydrous calcium carbonate phases, such as calcite, aragonite, and vaterite probably aid its formation and preservation. It is thought that perhaps the structure of calcium carbonate in a concentrated aqueous solution also consists of an ion pair, and that this is why ikaite readily nucleates at low temperatures, outside of its thermodynamic stability range. When removed from its natural cold water environment, ikaite rapidly disintegrates into monohydrocalcite or anhydrous calcium carbonate phases and water, earning the nickname of the melting mineral.
Pseudomorphs.
The presence of ikaite may be recorded through geological time through the presence of pseudomorphs of other calcium carbonate phases after it. Although it can be hard to uniquely define the original mineral for every specimen, there appears to be good evidence for ikaite as the precursor for the majority of the following locality names of pseudomorphs:
Ikaite or its pseudomorphs have been reported as occurring in marine, freshwater, and estuarine environments.
The common ingredient appears to be cold temperatures, although the presence of traces of other chemicals such as nucleation inhibitors for anhydrous calcium carbonate may also be required. It has also been reported as forming in winter on Hokkaido at a saline spring.
Since cold water can be found at depth in the oceans even in the tropics, ikaite can form at all latitudes. However, the presence of ikaite pseudomorphs can be used as a paleoclimate proxy or paleothermometry representing water near freezing conditions.
Thinolite deposits.
Thinolite is an unusual form of calcium carbonate found on the shore (Greek: "thinos" = shore) of Mono Lake, California. This and other lakes now largely in the desert or semi-desert environments of the southwestern US were part of a larger post-glacial lake that covered much of the region near the end of the last glaciation. It is thought that at this time, conditions similar to that of the Ikka fjord allowed for the growth of massive ikaite.
Isotope geochemistry.
Isotope geochemistry can reveal information about the origin of the elements that make up minerals. The isotopic composition of ikaite and the pseudomorphs is actively studied. Studies of the ratio of 13C to 12C in ikaite relative to a natural, standard ratio can help to determine the origin of the carbon pool (organic/inorganic) which was consumed to form ikaite. Some studies have shown that oxidizing methane is the source of both modern day ikaite and glendonites in high latitude, marine sediments. Similarly the ratio of 18O to 16O, which varies in nature with temperature and latitude, can be used to show that glendonites were formed in waters very close to the freezing point, in agreement with the observed formation of ikaite.


Bismuth oxynitrate

Bismuth oxynitrate is the name applied to a number of compounds that contain Bi3+, nitrate ions and oxide ions and which can be considered as compounds formed from Bi2O3, N2O5 and H2O. Other names for bismuth oxynitrate include bismuth subnitrate and bismuthyl nitrate. In older texts bismuth oxynitrate is often simply described as BiONO3. Bismuth oxynitrate was once called magisterium bismuti or bismutum subnitricum, and was used as a white pigment, in beauty care, and as a gentle disinfectant for internal and external use.
Bismuth oxynitrate is commercially available as Bi5O(OH)9(NO3)4 (CAS number: 1304-85-4) or as BiONO3·H2O (CAS Number 13595-83-0).
Some compounds have been fully characterised with single crystal studies and found to contain the octahedral [Bi6Ox(OH)8−x](10-x)+ cation. There is indirect evidence that either the octahedral cation Bi6O4(OH)46+ or the octahedral cation Bi6(OH)126+ is present in aqueous solution following the polymerisation of Bi(H2O)83+, the Bi3+ ion present in acidic solutions. The ion Bi6O4(OH)46+ is found in the perchlorate compound Bi6O4(OH)4ClO4·7H2O and is isoelectronic with the octahedral Sn6O4(OH)4 cluster found in the hydrate of tin(II) oxide, 3SnO·H2O. The compounds that contain this are:-
The compound Bi6O5(OH)3(NO3)5.3H2O(equivalent to 6Bi2O3.5N2O5.9H2O) also contains the octahedral units but this time they are joined to form {[Bi6O5(OH)3]5+}2.
Additionally some oxynitrates have layer structures (a common motif also found in bismuth(III) oxyhalides):-
Cluster cation structure.
The octahedral ion has 6 Bi3+ ions at the corners of an octahedron. There is no covalent bond between the Bi atoms, they are held in position by bridging O2− and OH− anions, one at the centre of each of the eight triangular faces, bridging three Bi ions. The Bi ions are essentially four coordinate and are at the apex of a flat square pyramid. An ab initio theoretical study of the hydration mechanism of Bi3+ and the structure concludes that the lone pairs on the Bi3+ ions are stereochemically active.
Preparation of bismuth oxynitrates.
Bismuth oxynitrates can be prepared from bismuth(III) nitrate. For example, hydrolysis of a solution of bismuth nitrate through the addition of alkali or the reaction of the pentahydrate, BiNO3·5H2O with KOH, or the controlled thermal decomposition of the pentahydrate.
The thermal decomposition of bismuth nitrate pentahydrate proceeds through the following stages
The final oxynitrate product of thermal dehydration is believed to be Bi5O7NO3, which is isostructural with β–Bi5O7I and has a layer structure. The ultimate stage of thermal decomposition of oxynitrates is bismuth(III) oxide, Bi2O3.


Strontium ranelate

Strontium ranelate, a strontium(II) salt of ranelic acid, is a medication for osteoporosis marketed as Protelos or Protos by Servier. Studies indicate it can also slow the course of osteoarthritis of the knee. The drug is unusual in that it both increases deposition of new bone by osteoblasts and reduces the resorption of bone by osteoclasts. It is therefore promoted as a "dual action bone agent" (DABA).
On 13 May 2013, Servier released a Direct Healthcare Professional Communication which stated that new restrictions for the use of strontium ranelate are now in place, as randomised trials have shown an increased risk of myocardial infarction. Servier states that the use is now restricted to treatment of severe osteoporosis in postmenopausal women at high risk for fracture. The European Pharmacovigilance Risk Assessment Committee (PRAC) recommends restriction in the use of strontium ranelate, based on a routine benefit-risk assessment of the medicine, which included data showing an increased risk of heart problems, including heart attacks. On 21 February 2014 the European Medicine Agency recommended that strontium ranelate remain available with restrictions relative to patients with existing heart disease.
Uses.
Strontium ranelate is registered as a prescription drug in more than 70 countries for the treatment of post-menopausal osteoporosis to reduce the risk of vertebral and hip fractures. In the United States, strontium ranelate is not approved by the FDA. In the United Kingdom, strontium ranelate is prescribed under the National Health Service as a medicine for the treatment of post menopausal osteoporosis.
2 major phase III clinical studies, SOTI (Spinal Osteoporosis Therapeutic Intervention) and TROPOS (Treatment of Peripheral Osteoporosis), were started in 2000 to investigate the efficacy of strontium ranelate in reducing vertebral fractures and peripheral fractures, including hip fractures. In the 3 years results, reported in 2004, strontium ranelate showed significant reduction in vertebral fractures with 41% and hip fractures with 36% compared with patients treated with placebo.
The efficacy was sustained in 5 years data. The 5 years data confirmed that strontium ranelate can reduce the vertebral fractures significantly no matter the risk factors of the osteoporotic women have. These include their age (<70, 70–80 and >80), bone mineral density (osteoporotic and osteopenia), prevalent fractures (0 prevalent fracture, 1–2 prevalent fractures and >2 prevalent fractures), symptomatic fractures, body mass index and smoking.
Strontium ranelate shows anti-fracture efficacy in very old elderly and osteopenic patients.
Contraindications.
Strontium ranelate is contraindicated in hypersensitivity to the active substance or to any of the excipients. It is not recommended in patients with severe renal disease, i.e. creatinine clearance below 30 mL/min due to lack of data. Precaution is advised in patients at increased risk of venous thromboembolism (VTE), including patients with a history of VTE. Precaution is advised in patients with phenylketonuria, as formulations of strontium ranelate contain phenylalanine. Precaution as it interferes with colorimetric measurements of calcium in blood and urine.
Side effects.
Strontium ranelate increased the risk of venous thromboembolism, pulmonary embolism and serious cardiovascular disorders, including myocardial infarction. Its use is now restricted.
The most common side effects include nausea, diarrhea, headache and eczema, but with only 2–4% increase compared with placebo group. However, most of those side effects resolved within 3 months. Occasional severe allergic reactions have been reported including drug rash with eosinophilia and systemic symptoms (DRESS syndrome)
Interactions.
According to the manufacturer, strontium ranelate should be taken 2 hours apart from food, milk and derivative products, and medicinal products containing calcium. Should be taken 2 hours before antacids. Treatment should be suspended while taking oral tetracycline and quinolone antibiotics, as these chelate the strontium ion.
Pharmacology.
Mechanism of action.
Strontium, which has the atomic number 38, belongs to group II in the periodic table of elements, just beneath calcium. Because its nucleus is very nearly the same size as that of calcium, the body easily takes up strontium and incorporates it into bones and tooth enamel in place of calcium. This is not a health problem, and in fact, it can provide a health benefit. For example, in clinical trials, the drug strontium ranelate was found to aid bone growth, increase bone density, and lessen vertebral, peripheral, and hip fractures in women.
Strontium ranelate is an antiosteoporotic agent which both increases bone formation and reduces bone resorption, resulting in a rebalance of bone turnover in favor of bone formation. This is similar to the effects of choline-stabilized orthosilicic acid.
Strontium ranelate stimulates the calcium-sensing receptors and leads to the differentiation of pre-osteoblast to osteoblast which increases the bone formation. Strontium ranelate also stimulates osteoblasts to secrete osteoprotegerin in inhibiting osteoclasts formed from pre-osteoclasts in relation to the RANKL system, which leads to the decrease of bone resorption.
Research.
A large international study, the "Strontium Ranelate Efficacy in Knee Osteoarthritis trial," or SEKOIA, reported in 2012 that the drug significantly slowed the course of knee OA compared to placebo in a double-blind ransomised controlled trial. The drug reduced knee OA pain symptoms, improved function, and reduced x-ray detectable cartilage loss, as shown by reductions in joint space narrowing over three years.
References.
Cessation of marketing of Protelos/Osseor: Extract of the letter sent to European Medicine Agency (EMA) and national European Agencies on 10 February 2017


Native vanadium

Native vanadium is the mineral form of the metal vanadium, with the accepted name "vanadium". This exceedingly rare mineral was found among fumaroles of the Colima volcano. Fumaroles of Colima are known of being vanadium-rich, depositing other vanadium minerals, that include shcherbinaite (V2O5) and colimaite (K3VS4).


Molybdenum(II) acetate

Molybdenum(II) acetate is a coordination compound with the formula Mo2(O2CCH3)4. It is a yellow, diamagnetic, air-stable solid that is slightly soluble in organic solvents. Molybdenum(II) acetate is an iconic example of a compound with a metal-metal quadruple bond.
Structure and bonding.
It adopts the same Chinese lantern structure as related acetate dimers such as rhodium(II) acetate, copper(II) acetate, and chromium(II) acetate. Each Mo(II) center in Mo2(O2CCH3)4 has four d valence electrons. These eight d-electrons form one σ, two π bonds, and one δ bond, creating a bonding electron configuration of σ2π4δ2. Each of these bonds are formed by the overlapping of pairs of d orbitals. The four acetate groups bridge the two metal centers. The Mo-O bond between each Mo(II) center and O atom from acetate has a distance of 2.119 Å, and the Mo-Mo distance between the two metal centers is 2.0934 Å.
Preparation.
Mo2(O2CCH3)4is prepared by treating molybdenum hexacarbonyl (Mo(CO)6) with acetic acid. The process strips CO ligands from the hexacarbonyl and results in the oxidation of Mo(0) to Mo(II).
Trinuclear clusters are byproducts.
The reaction of HO2CCH3 and Mo(CO)6 was first investigated by Bannister et al. in 1960. At the time, quadruple metal-metal bonds had not yet been discovered, so these authors proposed that Mo(O2CCH3)2 was tetrahedral. This perspective changed with Mason's characterization.
Applications.
Mo2(O2CCH3)4 is generally used as an intermediate compound in a process to form other quadruply bonded molybdenum compounds. The acetate ligands can be replaced to give new compounds such as [Mo2Cl8]4− and Mo2Cl4[P(C4H9)3]4.


Ethylmercury

Ethylmercury (sometimes ethyl mercury) is a cation composed of an organic CH3CH2- species (an ethyl group) bound to a mercury(II) centre, making it a type of organometallic cation, and giving it a chemical formula C2H5Hg+. The main source of ethylmercury is thimerosal.
Synthesis and structure.
Ethylmercury (C2H5Hg+) is a substituent of compounds: it occurs as a component of compounds of the formula C2H5HgX where X = chloride, thiolate, or another organic group. Most famously X = the mercaptide group of thiosalicylic acid as in thiomersal. In the body, ethylmercury is most commonly encountered as derivatives with a thiolate attached to the mercury. In these compounds, Hg(II) has a linear or sometimes trigonal coordination geometry. Given the comparable electronegativities of mercury and carbon, the mercury-carbon bond is described as covalent.
Toxicity.
The toxicity of ethylmercury is well studied. Like methylmercury, ethylmercury distributes to all body tissues, crossing the blood–brain barrier and the placental barrier, and ethylmercury also moves freely throughout the body. Risk assessment for effects on the human nervous system have been made by extrapolating from dose-response relationships for methylmercury. Estimates have suggested that ethylmercury clears from blood with a half-life of 3–7 days in adult humans, however this area has not been well studied.
Public health concerns.
Concerns based on extrapolations from methylmercury caused thiomersal to be removed from U.S. childhood vaccines, starting in 1999, but remains in all multi dose vaccines and flu shots (though many single use vaccines with no thimerosal are available). Clarkson has argued that risk assessments based on methylmercury were overly conservative, in light of observations that ethylmercury is eliminated from the body and the brain significantly faster than methylmercury. Moreover, Clarkson has argued that inorganic mercury metabolized from ethylmercury, despite its much longer half-life in the brain, is much less toxic than the inorganic mercury produced from mercury vapor, for reasons not yet understood.


Hyperammonemia

Hyperammonemia is a metabolic disturbance characterised by an excess of ammonia in the blood. It is a dangerous condition that may lead to brain injury and death. It may be primary or secondary.
Ammonia is a substance that contains nitrogen. It is a product of the catabolism of protein. It is converted to the less toxic substance urea prior to excretion in urine by the kidneys. The metabolic pathways that synthesize urea involve reactions that start in the mitochondria and then move into the cytosol. The process is known as the urea cycle, which comprises several enzymes acting in sequence. It is greatly exacerbated by common zinc deficiency, which raises ammonia levels further.
Signs and symptoms.
Complication.
Hyperammonemia is one of the metabolic derangements that contribute to hepatic encephalopathy, which can cause swelling of astrocytes and stimulation of NMDA-receptors in the brain. Overstimulation of NMDA-receptors induces excitotoxicity.
Diagnosis.
Types.
Specific types.
The following list includes such examples:
Treatment.
Treatment centers on limiting intake of ammonia and increasing its excretion. Dietary protein, a metabolic source of ammonium, is restricted and caloric intake is provided by glucose and fat. Intravenous arginine (argininosuccinase deficiency), sodium phenylbutyrate and sodium benzoate (ornithine transcarbamoylase deficiency) are pharmacologic agents commonly used as adjunctive therapy to treat hyperammonemia in patients with urea cycle enzyme deficiencies. Sodium phenylbutyrate and sodium benzoate can serve as alternatives to urea for the excretion of waste nitrogen. Phenylbutyrate, which is the product of phenylacetate, conjugates with glutamine to form phenylacetylglutamine, which is excreted by the kidneys. Similarly, sodium benzoate reduces ammonia content in the blood by conjugating with glycine to form hippuric acid, which is rapidly excreted by the kidneys. A preparation containing sodium phenylacetate and sodium benzoate is available under the trade name Ammonul.
Acidification of the intestinal lumen using lactulose can decrease ammonia levels by protonating ammonia and trapping it in the stool. This is a treatment for hepatic encephalopathy.
Treatment of severe hyperammonemia (serum ammonia levels greater than 1000 μmol/L) should begin with hemodialysis if it is otherwise medically appropriate and tolerated.


Scandium nitrate

Scandium(III) nitrate, Sc(NO3)3, is an ionic compound. It is an oxidizer, as all nitrates are. The salt is applied in optical coatings, catalysts, electronic ceramics and the laser industry.


Uranium(III) chloride

Uranium(III) chloride, UCl3, is a chemical compound that contains the earth metal uranium and chlorine. UCl3 is used mostly to reprocess spent nuclear fuel. Uranium(III) chloride is synthesized in various ways from uranium(IV) chloride; however, UCl3 is less stable than UCl4.
Preparation.
There are two ways to synthesize uranium(III) chloride. The following processes describe how to produce uranium(III) chloride.
(1) In a mixture of NaCl-KCl at 670–710 °C, add uranium tetrachloride with uranium metal.
(2) Heat uranium(IV) chloride in hydrogen gas.
Properties.
In solid uranium(III) chloride each uranium atom has nine chlorine atoms as near neighbours, at approximately the same distance, in a tricapped trigonal prismatic configuration.
Uranium(III) chloride is a green crystalline solid at room temperature. UCl3 melts at 837 °C and boils at 1657 °C. Uranium(III) chloride has a density of 5500 kg/m3 or 5.500 g/cm3.
Its composition by weight:
Its formal oxidative states:
Uranium(III) chloride is very soluble in water and is also very hygroscopic. UCl3 is more stable in a solution of hydrochloric acid.
Uses.
Reagent.
Uranium(III) chloride is used in reactions with tetrahydrofuran (THF) and sodium methylcyclopentadiene to prepare various uranium metallocene complexes.
Catalyst.
Uranium(III) chloride is used as a catalyst during reactions between lithium aluminium hydride (LiAlH4) and olefins to produce alkyl aluminate compounds.
Molten form.
The molten form of uranium(III) chloride is a typical compound in pyrochemical processes as it is important in the reprocessing of spent nuclear fuels. UCl3 is usually the form that uranium takes as spent fuel in electrorefining processes.
Hydrates.
There are three hydrates of uranium(III) chloride:
Each are synthesized by the reduction of uranium(IV) chloride in methylcyanide (acetonitrile), with specific amounts of water and propionic acid.
Precautions.
While there are no long-term data on the toxic effects thas UCl3, it is important to minimize exposure to this compound when possible.
Similar to other uranium compounds that are soluble, UCl3 is likely absorbed into the blood through the alveolar pockets of the lungs within days of exposure. Exposure to uranium(III) chloride leads to toxicity of the renal system.


Unquadoctium


Rubidium perchlorate

Rubidium perchlorate, RbClO4, is the perchlorate of rubidium. It is an oxidizing agent, as are all perchlorates.
Preparation and properties.
Rubidium perchlorate can be obtained through the careful heating of a rubidium chlorate solution, leading to a disproportionation reaction with the release of oxygen gas:
When heated, it decomposes into the chloride and oxygen:
It has two polymorphs. Below 279 °C, it crystallizes in orthorhombic crystal system with lattice constants "a" = 0.927 nm, "b" = 0.581 nm, "c" = 0.753 nm. Over 279 °C, it has a cubic structure with lattice constant "a" = 0.770 nm.
Table of solubility in water:


Magnesium salicylate

Magnesium salicylate is a common analgesic and nonsteroidal anti-inflammatory drug (NSAID) used to treat mild to moderate muscular pain. It is also used to treat headaches, general back pain, and certain joint pains like arthritis.
It is found in a variety of over-the-counter (OTC) medications, most notably the brand of such medication called "Doan's Pills," as an anti-inflammatory, primarily for back-pain relief. Magnesium salicylate can be an effective OTC alternative to prescription NSAIDs, with both anti-inflammatory and pain-relieving effects.
Controversy.
While magnesium salicylate is an alternative for pain relief, it still is an NSAID like others in its category and can cause stomach ulcers, without any proven superiority over other
over-the-counter type pain relievers (NSAID).
Doan's specifically, and the company producing it, Novartis, have been tried over their claim that the product is superior in providing back pain relief. In June 1996, the FTC (Federal Trade Commission) charged the company with violating federal law with its unsubstantiated claim. In March 1998, the court ruled in favor of the FTC, but there was no stipulation about how the company should or would have to amend its advertising/packaging. Thus, Doan's was able to continue marketing as a "superior treatment for back pain".
In May 1999 the FTC released a statement summarizing the proceedings and announced the commission's decision after a 4–0 vote imposing a penalty on Doan's and its marketer, Novartis, to "run ads to correct misbeliefs resulting from their unsubstantiated claim that Doan's Pills are superior to other over-the-counter analgesics for treating back pain" and to modify packaging to include the statement "Although Doan's is an effective pain reliever, there is no evidence that Doan's is more effective than other pain relievers for back pain." The ads were required to run for a period of one year.


Organorhodium chemistry

Organorhodium chemistry is the chemistry of organometallic compounds containing a rhodium-carbon chemical bond, and the study of rhodium and rhodium compounds as catalysts in organic reactions.
Stable organorhodium compounds and transient organorhodium intermediates are used as catalyst such as in olefin hydroformylation, olefin hydrogenation, olefin isomerization and the Monsanto process
Classification based on principal oxidation states.
Organometallic rhodium compounds share many characteristics with those of iridium, but less so with cobalt. Rhodium can exist in oxidation states of -III to +V, but rhodium(I) and rhodium(III) are the more common. Rhodium(I) compounds (d8 configuration) usually occur with square planar or trigonal bipyramidal geometries, while rhodium (III) compounds (d6 configuration) typically have an octahedral geometry.
Rhodium(0).
Rhodium(0) complexes are binary carbonyls, the principal examples being tetrarhodium dodecacarbonyl, Rh4(CO)10, and hexadecacarbonylhexarhodium, Rh6(CO)16. These compounds are obtained by reductive carbonylation of rhodium(III) salts or Rh2Cl2(CO)4. In contrast to the stability of the homologous Co2(CO)8, Rh2(CO)8 is very labile.
Rhodium(I).
Rhodium(I) complexes are important homogeneous catalysts. Common complexes include bis(triphenylphosphine)rhodium carbonyl chloride, chlorobis(ethylene)rhodium dimer, cyclooctadiene rhodium chloride dimer, chlorobis(cyclooctene)rhodium dimer, dicarbonyl(acetylacetonato)rhodium(I), and rhodium carbonyl chloride. Although not formally organometallic, Wilkinson's catalyst (RhCl(PPh3)3), is included in the list of important catalysts. The simple olefin complexes chlorobis(ethylene)rhodium dimer, chlorobis(cyclooctene)rhodium dimer, and cyclooctadiene rhodium chloride dimer are often used as sources of "RhCl", exploiting the lability of the alkene ligands or their susceptibility to removal by hydrogenation. (η5-Cp)RhL2 are derived from Rh2Cl2L4 (L = CO, C2H4).
Rhodium(II).
Unlike the prevalence of cobalt(II) complexes, compounds of rhodium(II) are rare. The sandwich compound rhodocene is one example, even it exists in equilibrium with a dimeric Rh(I) derivative. Although not organometallic, rhodium(II) acetate (Rh2(OAc)4) catalyzes cyclopropanations via organometallic intermediates. Rhodium(II) porphyrin complexes react with methane.
Rhodium(III).
Rhodium is usually supplied commercially in the Rh(III) oxidation state, the main starting reagent being hydrated rhodium trichloride. The latter reacts with olefins and with CO to give organometallic complexes, often concomitant with reduction to Rh(I). Cyclopentadienyl complexes of rhodium include the half-sandwich compound pentamethylcyclopentadienyl rhodium dichloride dimer.
Rhodium(V).
Strong donor ligands - hydride, silyl, boryl - are required to stabilize Rh(V). This oxidation state is invoked in borylation reactions.
Major applications.
Despite its high cost, rhodium is heavily relied on as a commercial catalyst.
Acetic acid and acetic anhydride syntheses.
The Monsanto process is an industrial method for the manufacture of acetic acid by catalytic carbonylation of methanol, although it has largely been supplanted by the iridium-based Cativa process.
The catalytically active species is the anion "cis"-[Rh(CO)2I2]−. which undergoes oxidative addition with methyl iodide. The related Tennessee Eastman acetic anhydride process affords acetic anhydride by carbonylation of methyl acetate.
Hydroformylation.
Hydroformylations often rely on rhodium-based catalysts. Water-soluble catalysts have also been developed. They facilitate the separation of the products from the catalyst.
Hydrogenation.
Wilkinson's catalyst is used as a homogeneous catalyst for the hydrogenation of olefins. The mechanism of catalysis involves oxidative addition of H2, π-complexation of alkene, migratory insertion (intramolecular hydride transfer or olefin insertion), and reductive elimination.
Cationic organorhodium(I) catalysts are useful for asymmetric hydrogenations, which are applied to bioactive products such as pharmaceutical agents and agrochemicals.
Other reactions.
Nitrobenzene reduction is another reaction catalysed by this compound type:


Fluorellestadite

Fluorellestadite is a rare nesosilicate of calcium, with sulfate and fluorine, with the chemical formula Ca10(SiO4)3(SO4)3F2. It is a member of the apatite group, and forms a series with hydroxylellestadite.
Etymology.
The mineral was originally named wilkeite by Eakle and Rogers in 1914, in honor of R. M. Wilke, a mineral collector and dealer. In 1922, a sample of “wilkeite” was analysed and found to be sufficiently different from the material reported by Eakle and Rogers to consider it a new species. The name “ellestadite” was proposed, in honor of Reuben B Ellestad (1900–1993), an American analytic chemist from the Laboratory for Rock Analysis, University of Minnesota, US.
In 1982 Rouse and Dunn showed that the Si:S ratio was close to 1:1, giving the formula Ca10(SiO4)3(SO4)3X2, where X represents fluorine (F), hydroxyl (OH) or chlorine (Cl), and they named minerals in this group the ellestadite group. The end members of the group were named hydroxylellestadite (X = OH), fluorellestadite (X = F) and chlorellestadite (X = Cl); ideal end-member chlorellestadite is assumed not to exist in nature, although it has been synthesized. Wilkeite was discredited as a unique species, as it is not an end member of any solid solution series, but an intermediate member.
The name fluorellestadite was changed to ellestadite-(F) in 2008 and changed back to fluorellestadite in 2010.
Structure.
The ellestadites are nesosilicates, which are minerals with isolated SiO4 tetrahedra. They are members of the apatite group, but whereas phosphorus is one of the chief constituents of apatite, in ellestadite it is almost completely replaced by sulfur and silicon, without appreciably altering the structure. The crystal class is hexagonal 6/m, space group P63/m. The tetrahedral groups are arranged to create the 63 screw axis, and the fluorine atoms are located in channels parallel to this direction. Some sources give unit cell parameters for one formula unit per unit cell (Z = 1), but some scientists consider the formula to be half the value accepted by the International Mineralogical Association (IMA), i.e. Ca5((Si,S)O4))3F, with two formula units per unit cell (Z = 2). Cell parameters for natural, as opposed to synthetic, material are a = 9.41 to 9.53 Å, and c = 6.90 to 6.94 Å. Rouse and Dunn postulated a hypothetical pure end-member with a = 9.543 Å and c = 6.917 Å. Synthetic material has a = 9.53 to 9.561 Å, and c = 6.91 to 6.920 Å.
Appearance.
Fluorellestadite occurs as acicular or hexagonal prismatic, poorly terminated crystals, and as fine-grained aggregates. Crystals are transparent and aggregates are translucent. Material from Crestmore, California, is light rose-red or yellow in color, and typically occurs in a matrix of blue calcite. Material from Russia is pale bluish-green or colorless. The streak is white with a weak bluish tint, and the luster is sub-resinous on broken surfaces, but very brilliant on prism faces.
Physical properties.
Fluorellestadite shows imperfect cleavage perpendicular to the long crystal axis. The mineral is very brittle, and breaks with a conchoidal fracture. Its hardness is , between that of fluorite and apatite, and its specific gravity is 3.03 to 3.07, similar to that of fluorite. It is easily soluble in dilute hydrochloric and nitric acids and is not radioactive. When intensely heated, ellestadite (wilkeite) becomes colorless and then assumes a pale bluish green color on cooling.
The mineral is uniaxial (-), with refractive indices nω = 1.638 to 1.655 and nε = 1.632 to 1.650. It is sometimes fluorescent, white to blue-white or yellow-white in short-wave ultraviolet light, and medium white-yellow-brown or weak white in long-wave light.
Occurrence and associations.
The type locality is Coal Mine No. 44, Kopeisk, Chelyabinsk coal basin, Chelyabinsk Oblast, Southern Urals, Russia, and type material is held at the Fersman Mineralogical Museum, Academy of Sciences, Moscow, Russia.
Ellestadite is a skarn mineral. It occurs associated with diopside, wollastonite, idocrase, monticellite, okenite, vesuvianite, calcite and others at Crestmore, Riverside County, California, US. At Crestmore a contact zone exists between crystalline limestone and granodiorite. The area was quarried for limestone in the early 1900s, revealing varied associations of metamorphic minerals, including ellestadite (named as wilkeite) with garnet, vesuvianite and diopside, in blue calcite. At the type locality it was formed in burned fragments of petrified wood in coal dumps, associated with lime, periclase, magnesioferrite, hematite, srebrodolskite and anhydrite. Ellestadite (wilkeite) is often altered to okenite.