Hydrides of alkali metals

Reacts with calcium and magnesium hydrides in tetrahydrofuran forming tetrahydro aluminates, Ca(AlH4)2 reacts with hydrides of alkali metals in ether forming aluminum hydride ... 

POTASSIUM lODATE (7758-05-6) Noncombustible, but many chemical reactions can cause fire and explosions. A strong oxidizer. Reacts violently with many materials, including reducing agents, combustible materials, organic substances, manganese dioxide, arsenic, finely divided metals or carbon materials, hydrides of alkali metals or alkaline earths, metal cyanides, metal thiocyanates, phosphonium iodide, red phosphorus, sulfides, sulfur, xenon tetrafluoride. Forms explosive compounds with solid organic matter. Attacks chemically active metals (e.g., aluminum, copper, zinc, etc.). 

The high-boiling polar organic solvents - dimethylsulfoxide, sulfolane, dimethylsulfone, dimethylformamide, dimethylacetamide - are generally used for synthesizing the polyesterketones and polyesteresterketones by means of polycondensation in this case the reaction catalysts are the anhydrous hydroxides, carbonates, fluorides and hydrides of alkali metals. 

Table 1. Physical Properties of Alkali Metal Hydrides...

The main methods of reducing ketones to alcohols are (a) use of complex metal hydrides (b) use of alkali metals in alcohols or liquid ammonia or... 

High inhibitive efficiency relative to thermal destruction of n-alkanes is displayed by hydrides and amides of alkali metals [33-35]. 

In anionic polymerization, as in carbonium ion polymerization, termination does not involve bimolecular reaction between two growing chains. Neither can recombination of ions lead to termination, since a carbon-metal bond is highly polar, in the case of alkali metals frequently completely ionized, and in every case very reactive. The termination step leading to the formation of a terminal C=C double bond is not too probable. This reaction involves the formation of a metal hydride, and this does not contribute greatly to the driving force. Consequently, such a termination is observed at higher temperatures only and it is probably more common in coordination polymerization where the metals involved are less electropositive. 

Perhaps of more significance is a detailed study132 into the reductive desulphonylation of 7-methyl-7-phenylsulphonylestratrienes. The goal was stereoselective removal of the sulphonyl group, and hydride reductions, alkali-metal-amalgam reductions and electrochemical reductions were explored. The latter proved to be the most effective and the best results are illustrated in Scheme 3. 

Brown, H. C., The Reactions of Alkali Metal Hydrides and Boro-hydrides with Lewis Acids of Boron and Aluminum, Congr. Lect., 17th Int. Congr. Pure Appl. Chem. p. 167. Butterworths, London, 1960. 

The interstitial hydrides of transition metals differ from the salt-like hydrides of the alkali and alkaline-earth metals MH and MH2, as can be seen from their densities. While the latter have higher densities than the metals, the transition metal hydrides have expanded metal lattices. Furthermore, the transition metal hydrides exhibit metallic luster and are semiconducting. Alkali metal hydrides have NaCl structure MgH2 has rutile structure. 

The synthesis of alkali metal organophosphides and arsenides is usually most conveniently achieved by the direct metalation of a primary or secondary phosphine/arsine with a strong deprotonating agent such as an alkyllithium or an alkali metal hydride ... 

Intimate mixtures of chlorates, bromates or iodates of barium, cadmium, calcium, magnesium, potassium, sodium or zinc, with finely divided aluminium, arsenic, copper carbon, phosphorus, sulfur hydrides of alkali- and alkaline earth-metals sulfides of antimony, arsenic, copper or tin metal cyanides, thiocyanates or impure manganese dioxide may react violently or explosively, either spontaneously (especially in presence of moisture) or on initiation by heat, friction, impact, sparks or addition of sulfuric acid [1], Mixtures of sodium or potassium chlorate with sulfur or phosphorus are rated as being exceptionally dangerous on frictional initiation. 

Phase-transfer catalytic conditions provide an extremely powerful alternative to the use of alkali metal hydrides for the synthesis of cyclopropanes via the reaction of dimethyloxosulphonium methylides with electron-deficient alkenes [e.g. 54-56] reaction rates are increased ca. 20-fold, while retaining high yields (86-95%). Dimethylphenacylsulphonium bromide reacts in an analogous manner with vinyl-sulphones [57] and with chalcones [58] and trimethylsulphonium iodide reacts with Schiff bases and hydrazones producing aziridines [59]. 

With Hydrides. —As has already been stated, the hydrides of the metals of the alkali and alkaline earth groups produce hydrogen on being placed in water. However, in only two cases are these reactions worth consideration. 

On looking into the literature to see whether this value of d(ff) = 0.28 A is meaningful, it was found [1] that this is the value suggested by Pauhng [8] to account for the radius of H in the partially ioitic bonds in hydrogen halides and in alkali metal hydrides The author then used this value of d(H+) = 0.28 A to estimate the radii of alkali metal ions from the observed bond distances d(MH) j in the metal hydrides, MH. It was a pleasant surprise to find that,... 

L. Elansari, L. Antoine, R. Janot, J.C. Gachon, J.J. Kuntz, D. Guerard, Preparation of alkali metal hydrides by mechanical alloying, J. Alloys Compd. 329 (2001) L5-L8. 

Chemicals that are water or air reactive pose a significant fire hazard because they may generate large amounts of heat. These materials may be pyrophoric, that is, they ignite spontaneously on exposure to air. They may also react violently with water and certain other chemicals. Water-reactive chemicals include anhydrides, carbides, hydrides, and alkali metals (e.g., lithium, sodium, potassium). 

Alkyl chlorides are with a few exceptions not reduced by mild catalytic hydrogenation over platinum [502], rhodium [40] and nickel [63], even in the presence of alkali. Metal hydrides and complex hydrides are used more successfully various lithium aluminum hydrides [506, 507], lithium copper hydrides [501], sodium borohydride [504, 505], and especially different tin hydrides (stannanes) [503,508,509,510] are the reagents of choice for selective replacement of halogen in the presence of other functional groups. In some cases the reduction is stereoselective. Both cis- and rrunj-9-chlorodecaIin, on reductions with triphenylstannane or dibutylstannane, gave predominantly trani-decalin [509]. 

Zinc Bromate. Zn(Br03)2.6H20 mw 429.28 white deliq crysts mp 100° sp grav 2.566. V sol in w. Prepn is by treating Zn oxide with bromine w. Intimate mixts of the bromate with finely divided Al, As, Cu, C, P, S hydrides of alkali and alkaline earth metals, Sb sulfide, metal cyanides, K thiocyanate or impure Mn dioxide can react explosively (spontaneously in the pre-... 

The main methods of reducing ketones to alcohols are (a) use of complex metal hydrides (b) use of alkali metals in alcohols or liquid ammonia or amines 221 (c) catalytic hydrogenation 14,217 (d) Meerwein-Ponndorf reduction.169,249 The reduction of organic compounds by complex metal hydrides, first reported in 1947,174 is a widely used technique. This chapter reviews first the main metal hydride reagents, their reactivities towards various functional groups and the conditions under which they are used to reduce ketones. The reduction of ketones by hydrides is then discussed under the headings of mechanism and stereochemistry, reduction of unsaturated ketones, and stereochemistry and selectivity of reduction of steroidal ketones. Finally reductions with the mixed hydride reagent of lithium aluminum hydride and aluminum chloride, with diborane and with iridium complexes, are briefly described. 

The only new compound produced in these studies was LiAlF4 however, this work is significant because control was achieved even with the highly exothermic reactions of lithium aluminum hydride, alkali metal borohydrides, and alkali metal hexahydroaluminated with elemental fluorine. The reactions of alkali metal amides with fluorine have also been successfully controlled. These reactions provide extremely clean routes to the fluoride analogues. 

The alkali metal hydrides contain alkali metal cations and H- anions in a face-centered cubic crystal structure like that of sodium chloride (Section 10.9). Alkali metal hydrides are also ionic in the liquid state, as shown by the fact that the molten compounds conduct electricity. 

The decisive point of the novel scheme is the amortization of CioHgLi by the elimination of the metal hydride. The authors admit that the weakness of their scheme is the lack of evidence for the formation of alkali metal hydride and for the formation of H2 from the (supposed) reaction between the protonating agent and the alkali metal hydride. However, the main sense of this scheme consists of its better agreement with the observed stoichiometry. As to the first step of Scheme 1-27 (the proton landing), it can certainly have a more intimate mechanism, say, electron transfer from the anion radical to the protonating... 

Bulky stannyl anions which are not available from stannyl hydrides (see Section I.A.l) were prepared by using the reaction of alkali metals with tin halides (equations 24 - 26)31,40 41. 

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