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Hexamethyldisilazane
Bis(trimethylsilyl)amine (also known as hexamethyldisilazane and HMDS) is an organosilicon compound with the molecular formula CH3)3Sisub>2NH. The molecule is a derivative of ammonia with trimethylsilyl groups in place of two hydrogen atoms. An electron diffraction study shows that silicon-nitrogen bond length (173.5 pm) and Si-N-Si bond angle (125.5°) to be similar to disilazane (in which methyl groups are replaced by hydrogen atoms) suggesting that steric factors are not a factor in regulating angles in this case. This colorless liquid is a reagent and a precursor to bases that are popular in organic synthesis and organometallic chemistry. Additionally, HMDS is also increasingly used as molecular precursor in chemical vapor deposition techniques to deposit silicon carbonitride thin films or coatings. Synthesis and derivatives Bis(trimethylsilyl)amine is synthesized by treatment of trimethylsilyl chloride with ammonia: :2 (CH3)3SiCl + 3 NH3 → CH3)3Sisub>2NH + 2 NH4Cl Ammoniu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HMDS USES '', a video game
{{disambiguation ...
HMDS may refer to: * either of two related reagents in organometallic chemistry: ** Hexamethyldisilazane ( CH3)3Sisub>2NH) ** Hexamethyldisilazide ( CH3)3Sisub>2NM) *** M = Li as in Lithium bis(trimethylsilyl)amide (LiHMDS) *** M = Na as in Sodium bis(trimethylsilyl)amide (NaHMDS) *** M = K as in Potassium bis(trimethylsilyl)amide (KHMDS) * Hexamethyldisiloxane (O i(CH3)3sub>2) * Her Majesty's Diplomatic Service, of the United Kingdom * Helmet mounted display and sight, a system for military pilots * ''Harvest Moon DS ''Harvest Moon DS'', known in Japan as , is a farm simulation role-playing video game for the Nintendo DS, part of the ''Story of Seasons'' series. It was published and developed by Marvelous Interactive Inc., and released in Japan on March 17, 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HMDS Application '', a video game
{{disambiguation ...
HMDS may refer to: * either of two related reagents in organometallic chemistry: ** Hexamethyldisilazane ( CH3)3Sisub>2NH) ** Hexamethyldisilazide ( CH3)3Sisub>2NM) *** M = Li as in Lithium bis(trimethylsilyl)amide (LiHMDS) *** M = Na as in Sodium bis(trimethylsilyl)amide (NaHMDS) *** M = K as in Potassium bis(trimethylsilyl)amide (KHMDS) * Hexamethyldisiloxane (O i(CH3)3sub>2) * Her Majesty's Diplomatic Service, of the United Kingdom * Helmet mounted display and sight, a system for military pilots * ''Harvest Moon DS ''Harvest Moon DS'', known in Japan as , is a farm simulation role-playing video game for the Nintendo DS, part of the ''Story of Seasons'' series. It was published and developed by Marvelous Interactive Inc., and released in Japan on March 17, 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithium Bis(trimethylsilyl)amide
Lithium bis(trimethylsilyl)amide is a lithiated organosilicon compound with the formula . It is commonly abbreviated as LiHMDS or Li(HMDS) (lithium hexamethyldisilazide - a reference to its conjugate acid HMDS) and is primarily used as a strong non-nucleophilic base and as a ligand. Like many lithium reagents, it has a tendency to aggregate and will form a cyclic trimer in the absence of coordinating species. Preparation LiHMDS is commercially available, but it can also be prepared by the deprotonation of bis(trimethylsilyl)amine with ''n''-butyllithium. This reaction can be performed ''in situ''. : Once formed, the compound can be purified by sublimation or distillation. Reactions and applications As a base LiHMDS is often used in organic chemistry as a strong non-nucleophilic base. Its conjugate acid has a p''K''a of ~26, making it is less basic than other lithium bases, such as LDA (p''K''a of conjugate acid ~36), but it is more sterically hindered and hence less nu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Bis(trimethylsilyl)amide
Sodium bis(trimethylsilyl)amide is the organosilicon compound with the formula . This species, usually called NaHMDS (sodium hexamethyldisilazide), is a strong base used for deprotonation reactions or base-catalyzed reactions. Its advantages are that it is commercially available as a solid and it is soluble not only in ethers, such as THF or diethyl ether, but also in aromatic solvents, like benzene and toluene by virtue of the lipophilic TMS groups. NaHMDS is quickly destroyed by water to form sodium hydroxide and bis(trimethylsilyl)amine. Structure Although the Na–N bond is polar covalent as a solid, when dissolved in nonpolar solvents this compound is trimeric, consisting of a central ring. Applications in synthesis NaHMDS is used as a strong base in organic synthesis. Typical reactions: *To deprotonate ketones and esters to generate enolate derivatives. *Generate carbenes by dehydrohalogenation of halocarbons. These carbene reagents add to alkenes to give substituted cy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyroglutamic Acid
Pyroglutamic acid (also known as PCA, 5-oxoproline, pidolic acid) is a ubiquitous but little studied natural amino acid derivative in which the free amino group of glutamic acid or glutamine cyclizes to form a lactam. The names of pyroglutamic acid conjugate base, anion, salts, and esters are pyroglutamate, 5-oxoprolinate, or pidolate. It is a metabolite in the glutathione cycle that is converted to glutamate by 5-oxoprolinase. Pyroglutamate is found in many proteins including bacteriorhodopsin. ''N''-terminal glutamic acid and glutamine residues can spontaneously cyclize to become pyroglutamate, or enzymatically converted by glutaminyl cyclases. This is one of several forms of blocked ''N''-termini which present a problem for ''N''-terminal sequencing using Edman chemistry, which requires a free primary amino group not present in pyroglutamic acid. The enzyme pyroglutamate aminopeptidase can restore a free ''N''-terminus by cleaving off the pyroglutamate residue. Pyroglutam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acetonitrile
Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not classed as organic). It is produced mainly as a byproduct of acrylonitrile manufacture. It is used as a polar aprotic solvent in organic synthesis and in the purification of butadiene. The skeleton is linear with a short distance of 1.16 Å. Acetonitrile was first prepared in 1847 by the French chemist Jean-Baptiste Dumas. Applications Acetonitrile is used mainly as a solvent in the purification of butadiene in refineries. Specifically, acetonitrile is fed into the top of a distillation column filled with hydrocarbons including butadiene, and as the acetonitrile falls down through the column, it absorbs the butadiene which is then sent from the bottom of the tower to a second separating tower. Heat is then employed in the separatin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xylene
In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are substituted determines which of three structural isomers results. It is a colorless, flammable, slightly greasy liquid of great industrial value. The mixture is referred to as both xylene and, more precisely, xylenes. Mixed xylenes refers to a mixture of the xylenes plus ethylbenzene. The four compounds have identical empirical formulas . Typically the four compounds are produced together by various catalytic reforming and pyrolysis methods. Occurrence and production Xylenes are an important petrochemical produced by catalytic reforming and also by carbonization, coal carbonisation in the manufacture of coke (fuel), coke fuel. They also occur in crude oil in concentrations of about 0.5–1%, depending on the source. Small quantities occur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glutamic Acid
Glutamic acid (symbol Glu or E; the ionic form is known as glutamate) is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can synthesize enough for its use. It is also the most abundant excitatory neurotransmitter in the vertebrate nervous system. It serves as the precursor for the synthesis of the inhibitory gamma-aminobutyric acid (GABA) in GABA-ergic neurons. Its molecular formula is . Glutamic acid exists in three optically isomeric forms; the dextrorotatory -form is usually obtained by hydrolysis of gluten or from the waste waters of beet-sugar manufacture or by fermentation.Webster's Third New International Dictionary of the English Language Unabridged, Third Edition, 1971. Its molecular structure could be idealized as HOOC−CH()−()2−COOH, with two carboxyl groups −COOH and one amino group −. However, in the solid state and mildly acidic water solutio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Encyclopedia Of Reagents For Organic Synthesis
The ''Encyclopedia of Reagents for Organic Synthesis'' is published in print and online by John Wiley & Sons Ltd. The online version is also known as e-EROS. The encyclopedia contains a description of the use of reagents used in organic chemistry. The eight-volume print version includes 3500 alphabetically arranged articles and the online version is regularly updated to include new reagents and catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...s. References External links *Print version Encyclopedias of science Chemistry books {{encyclopedia-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xanthine
Xanthine ( or ; archaically xanthic acid; systematic name 3,7-dihydropurine-2,6-dione) is a purine base (genetics), base found in most human body tissues and fluids, as well as in other organisms. Several stimulants are derived from xanthine, including caffeine, theophylline, and theobromine. Xanthine is a product on the pathway of purine degradation. * It is created from guanine by guanine deaminase. * It is created from hypoxanthine by xanthine oxidoreductase. * It is also created from xanthosine by purine nucleoside phosphorylase. Xanthine is subsequently converted to uric acid by the action of the xanthine oxidase enzyme. Use and manufacturing Xanthine is used as a drug precursor (chemistry), precursor for human and animal medications, and is manufactured as a pesticide ingredient. Clinical significance Derivatives of xanthine (known collectively as xanthines) are a group of alkaloids commonly used for their effects as mild stimulants and as bronchodilators, notably in the t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Derivative (chemistry)
In chemistry, a derivative is a compound that is derived from a similar compound by a chemical reaction. In the past, derivative also meant a compound that ''can be imagined to'' arise from another compound, if one atom or group of atoms is replaced with another atom or group of atoms, but modern chemical language now uses the term structural analog for this meaning, thus eliminating ambiguity. The term "structural analogue" is common in organic chemistry. In biochemistry, the word is used for compounds that at least theoretically can be formed from the precursor compound. Chemical derivatives may be used to facilitate analysis. For example, melting point (MP) analysis can assist in identification of many organic compounds. A crystalline derivative may be prepared, such as a semicarbazone or 2,4-dinitrophenylhydrazone (derived from aldehydes or ketones), as a simple way of verifying the identity of the original compound, assuming that a table of derivative MP values is available ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microwave Chemistry
Microwave chemistry is the science of applying microwave radiation to chemical reactions. Microwaves act as high frequency electric fields and will generally heat any material containing mobile electric charges, such as polar molecules in a solvent or conducting ions in a solid. Polar solvents are heated as their component molecules are forced to rotate with the field and lose energy in collisions. Semiconducting and conducting samples heat when ions or electrons within them form an electric current and energy is lost due to the electrical resistance of the material. Microwave heating in the laboratory began to gain wide acceptance following papers in 1986, although the use of microwave heating in chemical modification can be traced back to the 1950s. Although occasionally known by such acronyms as ''MAOS'' (microwave-assisted organic synthesis), ''MEC'' (microwave-enhanced chemistry) or ''MORE synthesis'' (microwave-organic reaction enhancement), these acronyms have had little acce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
