Potassium high dispersion

In 1973, the direct potassium metal reduction of zinc salts was reported.3 This active zinc powder reacted with alkyl and aryl bromides to form the alkyl- and arylzinc bromides under mild conditions.4 The reduction of anhydrous zinc salts by alkali metals can be facilitated through the use of electron carriers. Lithium and sodium naphthalenide reduce zinc salts to give highly reactive metal powders under milder and safer conditions. Graphite5 and liquid ammonia6 have also been employed as electron carriers in producing zinc powders. A highly dispersed reactive zinc powder was formed from the sodium metal reduction of zinc salts on titanium dioxide.7... 

Sodium metal may be dispersed by melting on various supporting solids (sodium carbonate, kieselguhr, etc.) or by high-speed stirring of a suspension of the metal in various hydrocarbon solvents held just above the melting point of the metal. Dispersions of the latter type may be poured in air, and they react with water only with effervescence. They are often used synthetically where sodium shot or lumps would react too slowly. Sodium and potassium, when dispersed on supports such as carbon, alumina, or silica are often more reactive than the metals. 

The potassium promoter is usually added as the carbonate but it was shown that the hydroxide, nitrate, fluoride, and the like, gave simQar results [15]. Highly-dispersed catalysts are formed when potassium/iron complex salts such as K Fe(C0)4 are supported on AljOj orSiOj [58]. After reduction,... 

The portions of elements which are not removed by either reagent are considered to be incorporated in acid-insoluble minerals, particularly clays, pyrite, and quartz. This group includes all of the silicon, the remaining sodium and potassium, and the residual iron, aluminium, and titanium. The acid-insoluble minerals are present as discrete phases. Frequently the mineral particles are quite small (see Figure 7, for example) and very highly dispersed through the... 

Potassium salts of hydrazones are also available by other procedures. Potassium amide has been used to generate potassium salts of monoaryl ketone hydrazones. The reactive intermediate generated in these cases is a dianion. Highly dispersed forms of potassium have also been reported to generate potassium salts from N.N-dimethylhydrazones at -60 C. The use of K/AI2O3 in metalation of aldehyde hydrazone anions produces modest yields of alkylated products in THF suspension. In hexane suspension, side reactions believed to include nitrile formation lead to lower synthetic yields of hydrazone pr ucts. 

Chlorine in the earth crust is not very abimdant and it is highly dispersed. Small amounts of this element are in the composition of numerous minerals and rocks. However, main source are chlorides of alkali and alkali-earth metals, first of all halite NaCl. Rarer are potassium, calcium, magnesium chlorides bischofite, carnallite, sylvin, sylvinite, kainite and other evaporite or lake salt. The important source of chlorine in ground water is also sea water. 

Alkanenitriles can be converted to alkanes by reductive decyanation with metallic sodium or potassium and several useful procedures are available. Sodium in liquid ammonia and potassium in HMPA are efficient reagents for the decyanation of alkanenitriles (equation 82). Sodium in the presence of tn s(acetylacetonato)iron III is a good combination for the reductive decyanation of primary and secondary alkanenitriles (equation 83). Highly dispersed potassium over alumina, easily prepared by melting potassium over dried alumina, converts primary, secondary and tertiary alkanenitriles to corresponding alkanes in good yield (equation 84) Recently, it has... 

At high temperatures the potassium was dispersed in atomic form, but on slow coohng to lower temperatures it could be condensed into colloidal aggregates. The halogens and hydrogen dissolved endothermically in halide lattices, the heats of solution being... 

When potassium thiocyanate (m.p. 173-179 C) is heated to about 430 C, the molten mass turns blue after cooling the color disappears. This phenomenon is probably due to the splitting-off of sulphur, which remains in highly dispersed colloidal form in the molten potassium thiocyanate, and which regenerates potassium thiocyanate on cooling ... 

Other preparation steps, such as loading the support with Pd and Au, washing, drying, reducing and promoting with potassium acetate, have also been optimized to contribute to the improvement of catalyst performance. The catalysts prepared by this modified method have a uniform distribution of highly dispersed Pd and Au... 

Aryl bromides can equally be coupled effectively with thiophenes 19 using the catalytic system tetrakis(triphenylphosphine)paIladium and potassium acetate (Scheme 10, Table 5) [39]. The use of highly dispersed palladium-polypyrrole... 

The nitrile group of 4-cyanopyridine is replaced quantitatively by hydrogen when treated with titanium trichloride in aqueous acetic acid. Under the same conditions, 2-cyanopyridine undergoes reductive decyanation only in poor yield, and 3-cyanopyridine is inert." Highly dispersed potassium on neutral alumina, easily prepared by melting potassium over alumina in an inert atmosphere, effects reductive cleavage of the cyano-group of alkyl nitriles in hexane at room temperature (e.g. Scheme 2). Alternatively, activated tertiary or secondary... 

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