Metal hydrides potassium hydride

Potassium 3-aniinopropylaniide [56038-00-7] (KAPA), KNHCH2CH2CH2-NH2, pX = 35, can be prepared by the reaction of 1,3-diaminopropane and potassium metal or potassium hydride [7693-26-7] (57—59). KAPA powder has been known to explode during storage under nitrogen in a drybox, and is therefore made in situ. KAPA is extremely effective in converting an internal acetylene or aHene group to a terminal acetylene (60) (see Acetylene-DERIVED chemicals). 

In KGjH4SiMe3, isolated as colorless, air-sensitive needles from the reaction between C5H5SiMe3 and potassium metal or potassium hydride,... 

Metal hydrides. Lithium hydride, sodium hydride, potassium hydride and lithium aluminium hydride all react violently with water liberating hydrogen the heat of reaction may cause explosive ignition. Excess metal hydride from a reaction must be destroyed by the careful addition of ethyl acetate or acetone. 

Metal Hydrides. Potassium, sodium, and copper hydrides ignite in chlorine.20... 

M-H (metal hydride) Sodium hydride Potassium hydride Strong, not nucleophilic base Deprotonation of weak organic acids with acidities as high as pKa 25... 

The simple procedure given below can be used for most solids, other than those which are extremely reactive with even the slightest amount of moisture or air. Examples of reagents which can be weighed by this method are sodium hydride, potassium hydride, lithium metal, lithium... 

NITROCARBOL (75-52-5) Forms explosive mixture with air (flash point 95°F/35°C). Thermally unstable. Shock, friction, pressure, or elevated temperature above 599°F/315°C can cause explosive decomposition, especially if confined. Violent reaction with strong oxidizers, alkyl metal halides, diethylaluminum bromide, formic acid, methylzinc iodide. Contact with acids, bases, acetone, aluminum powder, amines, bis(2-aminoethyl)amine, haolforms make this material more sensitive to explosion. Reacts, possibly violently, with ammonium hydroxide, calcium hydroxide, calcium hypochlorite, 1,2-diaminomethane, formaldehyde, hexamethylbenzene, hydrocarbons, hydroxides, lithium perchlorite, m-methyl aniline, nickel peroxide, nitric acid, metal oxides, potassium hydride, potassium hydroxide, sodium hydride. Mixtures with ammonia, aniline, diethylenetriamine, metal oxides, methyl amine, morpholine, phosphoric acid, silver nitrate form shock-sensitive compounds. Forms high-explosive compound with urea perchlorate. Mixtures with hydrocarbons and other combustible materials can cause fire and explosions. Attacks some plastics, rubber, and coatings. 

Hydrides commonly used in laboratories are lithium aluminum hydride, potassium hydride, sodium hydride, sodium borohydride, and calcium hydride. The following methods for their disposal demonstrate that the reactivity of metal hydrides varies considerably. Most hydrides can be decomposed safely by one of the four methods, but the properties of a given hydride must be well understood in order to select the most appropriate method. (CAUTION Most of the methods described below produce hydrogen gas, which can present an explosion hazard. The reaction shouid be carried out in a hood, behind a shield, and with proper safeguards to avoid exposure of the effluent gas to spark or flame. Any stirring device must be spark-proof.)... 

Normally C-alkylation involves the use of expensive condensing agents like sodamide, metal hydrides, potassium tertiary butoxide etc. and involves the use of anhydrous organic solvents. Due to the high selectivity of PTC, it is used for synthesis of monoalkyl derivatives of nitriles (Scheme 13). ... 

It is important to consider interactions between NHCs and alkali metals since, in many cases, NHCs are generated by deprotonation of a precursor molecule using an alkali salt of a strong base, such as potassium teri-butoxide, sodium hydride, potassium hydride, or u-butyllithium [19,20]. The influence of alkali metals in solution on stable diaminocarbenes has been investigated by C NMR and it has been postulated that metal ions in solution may act as catalysts for the dimerization of these NHCs [21]. Crystallographically characterized group 1 centers with coordinated neutral NHC ligands, however, are few and far between. 

Acetylene Bromine, chlorine, brass, copper and copper salts, fluorine, mercury and mercury salts, nitric acid, silver and silver salts, alkali hydrides, potassium metal... 

Potassium, Pubidium, and Cesium idjdrides. Although all the other alkah metal hydrides have been synthesized and some of the properties measured, only potassium hydride [7693-26-7] is commercially available. KH is manufactured in small amounts and sold as a mineral oil dispersion. It is a stronger base than NaH and is used to make the strong reducing agent KBH(C2H )2 and the super bases RNHK and ROK (6). 

KTB and KTA are superior to alkaU metal hydrides for deprotonation reactions because of the good solubiUties, and because no hydrogen is produced or oil residue left upon reaction. Furthermore, reactions of KTA and KTB can be performed in hydrocarbon solvents as sometimes requited for mild and nonpolar reaction conditions. Potassium alkoxides are used in large quantities for addition, esterification, transesterification, isomerization, and alkoxylation reactions. 

Potassium Hydride. Potassium hydride [7693-26-7] KH, made from reaction of molten potassium metal with hydrogen at ca 200°C, is suppHed in an oil dispersion. Pressure Chemical Company (U.S.) is a principal suppHer. KH is much more effective than NaH or LiH for enolization reactions (63,64). Use of KH as a base and nucleophile has been reviewed (65). 

MetaHic potassium and potassium—sodium alloys are made by the reaction of sodium with fused KCl (8,98) or KOH (8,15). Calcium metal and calcium hydride are prepared by the reduction of granular calcium chloride with sodium or sodium and hydrogen, respectively, at temperatures below the fusion point of the resulting salt mixtures (120,121). 

The drying of flammable solvents with sodium or potassium metal and metal hydrides poses serious potential fire hazards and adequate precautions should be stressed. 

The reduction of iminium salts can be achieved by a variety of methods. Some of the methods have been studied primarily on quaternary salts of aromatic bases, but the results can be extrapolated to simple iminium salts in most cases. The reagents available for reduction of iminium salts are sodium amalgam (52), sodium hydrosulfite (5i), potassium borohydride (54,55), sodium borohydride (56,57), lithium aluminum hydride (5 ), formic acid (59-63), H, and platinum oxide (47). The scope and mechanism of reduction of nitrogen heterocycles with complex metal hydrides has been recently reviewed (5,64), and will be presented here only briefly. 

In acidic electrolytes only lead, because it forms passive layers on the active surfaces, has proven sufficiently chemically stable to produce durable storage batteries. In contrast, in alkaline medium there are several substances basically suitable as electrode materials nickel hydroxide, silver oxide, and manganese dioxide as positive active materials may be combined with zinc, cadmium, iron, or metal hydrides. In each case potassium hydroxide is the electrolyte, at a concentration — depending on battery systems and application — in the range of 1.15 - 1,45 gem"3. Several elec-... 

Self-Test L.2A Calculate the mass of potassium metal needed to react with 0.450 g of hydrogen gas to produce solid potassium hydride, KH. 

A 20 g sample, prepared and stored in a dry box for several months, developed a thin crust of oxidation/hydrolysis products. When the crust was disturbed, a violent explosion occurred, later estimated as equivalent to 230 g TNT. A weaker explosion was observed with potassium tetrahydroaluminate. The effect was attributed to superoxidation of traces of metallic potassium, and subsequent interaction of the hexahydroaluminate and superoxide after frictional initiation. Precautions advised include use of freshly prepared material, minimal storage in a dry diluent under an inert atmosphere and destruction of solid residues. Potassium hydrides and caesium hexahydroaluminate may behave similarly, as caesium also superoxidises in air. 

Metal hydrides MRH Calcium hydride 5.35/37, Potassium hydride 4.98/52... 

See Hydrazine and derivatives, above Hydrogen sulfide Oxidants Non-metal hydrides, above Potassium phosphinate Air, or Nitric acid Sulfur dioxide, below... 

Potassium Potassium tert-butoxide Potassium hydride See under Alkali metals Organic compounds, sulfuric acid Air, chlorine, acetic acid, acrolein, acrylonitrile, maleic anhydride, nitroparaf-fins, /V-nitrosomethylurea, tetrahydrofuran, water... 

The importance of reactions with complex, metal hydrides in carbohydrate chemistry is well documented by a vast number of publications that deal mainly with reduction of carbonyl groups, N- and O-acyl functions, lactones, azides, and epoxides, as well as with reactions of sulfonic esters. With rare exceptions, lithium aluminum hydride and lithium, sodium, or potassium borohydride are the... 

Metal hydrides Germane, lithium aluminum hydride, potassium hydride, sodium hydride... 

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