Reactivity, of alkali metals

The reactivity of alkali metals with B decreases as their atomic number increases Li reacts completely with B at 700°C, whereas with K the reaction is not complete until 1200°C, at which T the pressure of the alkali metal is ca. 20 x 10 N m . These pressures demand the use of thick-walled reaction vessels. The boron-alkali metal mixture is placed in a Mo crucible inside such a container made of Fe or Mo, depending on the reaction T. 

The coordination of /3-diketonates and related species to alkali and alkaline earth cations has long been recognized. Combes first prepared Be(acac)2 in 1887,255 and the contribution of Sidgwick and Brewer concerning the nature of dihydrated alkali metal /3-diketonates plays a seminal role in the development of this area of coordination chemistry.19 A review concerning the structure and reactivity of alkali metal enolates has been written, 6 and sections on alkali and alkaline earth /3-diketonates can be found within more generalized accounts of /3-diketone complexes.257,258... 

Amides with electron-withdrawing substituents can be sufficiently labile towards nucleophilic attack to enable their use as protective groups. This is the case, for example, with trifluoro- [102,290] and trichloroacetamides [163], which are readily hydrolyzed under mild conditions (Figure 10.13). Suitable nucleophiles are hydrazine [291], aliphatic amines, and hydroxide, but if a hydrophobic support has been chosen, it must be borne in mind that the reactivity of alkali metal hydroxides will be reduced because of poor diffusion into the support. Amides of electron-poor amines (e.g. anilides) can also be readily cleaved by nucleophiles [292],... 

Tetr 32 2979 (1976) (regiospecific preparation of ketone enolates and synthetic uses) 33 2737 (1977) (structure and reactivity of alkali metal enolates)... 

These reactions were pioneered by Grice and co-workers who first addressed the reactivity of alkali metal dimers with halogen molecules [108-111]. These reactions are four-center harpoon reactions. They are interesting because of the possibility of two sequential electron jumps [112. ... 

The reactivity of alkali metals increases upon descending the column. By the time rubidium and cesium are reached, contact with the moisture in air would be explosive. 

These are mainly used in the study of reactions involving alkali metals. Because of the extreme reactivity of alkali metals it is impossible to have a reversible electrode of the type M(s) M+(aq) or M(s) MX(s) X (aq). This can be overcome by dissolving the alkali metal in Hg(l) which gives an alkali metal amalgam which is attacked much less vigorously by water. The Na(Hg) Na" "(aq) electrode is a common example of this type of electrode which behaves reversibly. 

The extremely high reactivity of alkali metal solutions calls for the utmost care in their handling. They must not be exposed to the air indeed, solutions such as potassium in hexamethylphosphoric-triamide are pyrophoric. Moisture and other adsorbed impurities have to be meticulously removed from all surfaces that come in contact with these reagents. A relatively simple technique to achieve this goal is described elsewhere1415. 

Reactions involving Enols or Enolic Derivatives.—A review of the structure and reactivity of alkali-metal enolates includes some steroidal reactions. A study of the mechanism of isomerization of androst-5-en-17/3-ol-3-one to testosterone indicated that the acid-catalysed process proceeds through rate-determining enolization whereas the base-catalysed reaction proceeds through rate-determining protonation of an enolate ion. Bromination of the 4,4,6-trimethyl-A -3-oxo-compounds (111)—(113) gave the 2a-bromo-derivatives, each of which showed anomalous o.r.d. curves. Bromination at C-2 was favoured for the... 

The alkali metals are easily vaporized at temperatures of 300—500"C, and most studies of this group have been reviewed in Sections 2 and 3. The reactivity of alkali metals in co-condensation reactions is high, but little different from that in diffusion flame studies. However, the alkali metals have been used in a number of low-temperature reactions, largely to produce radicals or intermediates of spectroscopic interest. For example, the trichloromethyl radical has been produced in a solid argon matrix by reaction of lithium atoms with carbon tetrachloride [294]. A similar technique has been used to produce the CBr2H radical from bromoform [295], the CCljH radical from chloroform [296], and the methyl radical from methyl iodide and methyl bromide [297]. In all these cases the corresponding lithium halide is produced. 

Kim, D.W. Jeong, H.-J. Lim, S.T. Sohn,M.-H. Katzenellenbogen, J.K. Chi, D.Y. Facile nucleophilic fluorination reactions using tert-alcohols as a reaction medium significantly enhanced reactivity of alkali metal fluorides and improved selectivity. J. Org. Chem. 2008, 75(3),957-962. 

The reactivity of alkali metals to water increases from top to bottom of the periodic table. For example, potassium reacts much more rapidly than lithium. They can also form oxides (For example, lithium can form oxides such as Li O.) and a variety of other compounds, since they are highly reactive. Alkali metals are good electrical and thermal conductors. All of them have one valence electron in their outer most shell, which is in the s orbital in the groimd state. The Group lA elements usually exhibit an oxidation state of+1. They have a valence shell configuration ofny. ... 

Alkylation.—The structure and reactivity of alkali-metal enolates has been reviewed, as have the regiospecific preparation and synthetic uses of ketone... 

L. M. Jackman and B. C. Lange, Structure and Reactivity of Alkali Metal Enolates , Tetrahedron, 1977, 33, 2737. 

In 1855, the Alsatian chemist Charles Adolphe Wurtz (1817-1884) observed the high reactivity of alkali metals with aliphatic halides (Eqs. 2.2a,b) and developed a C-C-coupHng method that was later named after him [3] ... 

A particular advantage of the elastomeric electrolyte is in the fabrication of on-chip power sources, in which thin film structures similar to those described above can be deposited directly as components on an integrated circuit. This technology has been demonstrated in principle but encapsulation problems have yet to be overcome due to the extreme reactivity of alkali metals. 

The reactivity of alkali metal clusters was also apparent from the outset when Rabo et al. [6] noted the reversible reaction of Na + with O2 to form adsorbed... 

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