Alkali metal carbides

Carbamoyl complexes from metal carbonyls and amines 5.8.2.12.4 Carbanions reactions with alkene complexes 5.8.2.3,4 metal carbonyls 5.8.2.S.5 Carbene complexes by alkene metathesis 5.8.2.3.11 formation 5.8.2.8.5 Carbides alkali metal formation 5.10.2.1 bonding 5.10.2 formation 5.10.2 industrial uses 5.10.2 interstitial formation 5.10.2 Carbometallacycle formation 5.S.2.2.2 Carbometallacycles from n-allyl complexes 5.S.2.3.9 Carbon reaction with alkali metals 5.10.2.1 Carbon dioxide complexes formation 5.8.2.14.1 Carbon monoxide displacement by alkenes 5.8.2.3.1 Carbonyl complexes by ligand exchange 5.8.2.12.2 from carbon monoxide 5.8.2.12.1, 5.8.2.12.2... 

Fixed-Bed Vapor-Phase Oxidation of Naphthalene. A sihca gel or sihcon carbide support is used for catalyst involved in the oxidation of naphthalene. The typical naphthalene oxidation catalyst is a mixture of vanadium oxide and alkali metal sulfate on the siUca support. Some changes, such as the introduction of feed vaporizers, are needed to handle a naphthalene feed (14), but otherwise the equipment is the same. 

Drying agents that combine irreversibly with water include the alkali metals, the metal hydrides (discussed in Chapter 2), and calcium carbide. 

The heavier alkaline earth metals Ca, Sr, Ba (and Ra) react even more readily with non-metals, and again the direct formation of nitrides M3N2 is notable. Other products are similar though the hydrides are more stable (p. 65) and the carbides less stable than for Be and Mg. There is also a tendency, previously noted for the alkali metals (p. 84), to form peroxides MO2 of increasing stability in addition to the normal oxides MO. Calcium, Sr and Ba dissolve in liquid NH3 to give deep blue-black solutions from which lustrous, coppery, ammoniates M(NH3)g can be recovered on evaporation these ammoniates gradually decompose to the corresponding amides, especially in the presence of catalysts ... 

Alkali-metal graphites are extremely reactive in air and may explode with water. In general, reactivity decreases with ease of ionization of M in the sequence Li > Na > K > Rb > Cs. Under controlled conditions H2O or ROH produce only H2, MOH and graphite, unlike the alkali-metal carbides M2C2 (p. 297) which produce hydrocarbons such as acetylene. In an important new reaction CgK has been found to react smoothly with transition metal salts in tetrahydrofuran at room temperature to give the corresponding transition metal lamellar compounds ... 

Carbon forms binary compounds with most elements those with metals are considered in this section whilst those with H, the halogens, O, and the chalcogens are discussed in subsequent sections. Alkali metal fullerides and encapsulated (endohedral) metallafullerenes have already been considered (pp. 285, 288 respectively) and met-allacarbohedrenes (metcars) will be dealt with later in this section (p. 300). Silicon carbide is discussed on p. 334. General methods of preparation of metal carbides are ... 

Substances which react with water to liberate flammable gas, e.g. carbides (liberate acetylene), alkali metals (hydrogen), organometallics (hydrocarbons - see Table 6.8), and where the heat of reaction is sufficient to ignite the gas. Thus metals which are less electronegative than hydrogen (see Table 6.10) will displace this element from water or alcohols, albeit at different rates. 

The mono- and di-alkali metal acetylides, copper acetylides, iron, uranium and zirconium carbides all ignite in chlorine, the former often at ambient temperature. See Caesium acetylide Halogens Dicopper(I) acetylide Halogens Iron carbide Halogens... 

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). 

Eor inert SAMs such as n-aUcanethiolates/Au, alkaline earth and alkali metal deposition on inert SAMs tends to exhibit low sticking coefficients of the nascent metal atoms due to quite weak interactions with the -CH3 terminus sometimes <10 of the impinging metal atoms stick to the surface while the rest scatter off the smface [23, 58]. Bammel and co-workers observed quite slow penetration of Na through this inert SAM [59]. In the case of Mg and Ca depositions on n-aUcanethiolate SAMs it was observed that while Mg does not react it does undergo continuous penetration thorough the SAM. In contrast, Ca does react to some extent resulting in calcium carbide species formation [56, 57]. In the case of K on an n-aUcanethiolate SAM the results are more complicated. For example, at 10 K atoms per SAM molecule, it has been reported that half of the deposited metal penetrates to the SAM/Au interface while the remainder is claimed to remain embedded within the SAM matrix [60], though such space is not available theoretically in a dense SAM. 

The general methods for the production of the alkali metals are (1) Electrolytic processes involving the electrolysis of (a) the fused hydroxide, or (b) a fused salt— chloride, nitrate, cyanide, etc. (2) Chemical processes involving the reduction of hydroxide, or carbonate, or other salt with carbon, metal carbide, iron, calcium, magnesium, aluminium, etc. W. Spring 5 claims to have reduced a little potassium chloride by passing hydrogen over the salt at a red heat. 

CARBIDES. A binary solid compound of carbon and another element. The most familiar carbides are those of calcium, tungsten, silicon, boron, and iron (cemcntitc) Two factors have an important bearing on the properties of carbides (1) the difference in electronegativity between carbon and the second elemenl. and (2) whether the second element is a transition metal. Saltlike carbides of alkali metals are obtained by reaction with acetylene. Those ohlained from silver, copper, and mercury sails are explosive. See also Carbon and Iron Metals, Alloys, and Steels. 

The metaniobates of the alkali metals, MNb03, the orthoniobates MjNbOj and the pyroniobates, M+NbeOy, where M is an alkali metal, can be prepared by various alkali carbonate or hydroxide fusion processes. Niobium fonns a nitride, NbN, and a carbide, NbC. 

Several of the mono- and di-alkali metal acetylides and copper acetylides ignite at ambient temperature or on slight warming, with either liquid or vapour. The alkaline earth, iron, uranium and zirconium carbides ignite in the vapour on heating. 

Finely powdered metals, diethyl ether, hydrogen, unsaturated organic compounds, carbide salts, acetylene, alkali metal Oxidizing agents... 

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