Inclusion of alkali metals

Pedersen used reactions of nucleophilic substitution to synthesize most of the crown ethers he has obtained. On the other hand, Lehn and his coworkers [17] (Fig. 7.1.4) carried out cyclization reactions involving amide formation under high dilution conditions in their quest for cryptands such as 54. Pedersen analysis of the selective inclusion of alkali metal cations into the crown ethers cavity... 

As can be appreciated in the examples illustrated in Table 4.14, a number of superconductors based on the inclusion of alkali metals and thalium have been prepared. Superconducting transition temperatures in these compounds are significantly higher than those observed for the correponding graphite intercalates. Apparently, in the case of the fullerenes there is a near linear relationship between the superconducting transition temperature, Tp, and the alkali metal size. Such a relationship, deduced from the correlation between Tp and the... 

We have not attempted to cover all or even most aspects of crown chemistry and some may say that the inclusions are eclectic. We felt that anyone approaching the field would need an appreciation for the jargon currently abounding and for the so-called template effect since the latter has a considerable bearing on the synthetic methodology. We have, therefore, included brief discussions of these topics in the first two chapters. In chapters 3—8, we have tried to present an overview of the macrocyclic polyethers which have been prepared. We have taken a decidedly organic tack in this attempting to be comprehensive in our inclusion of alkali and alkaline earth cation binders rather than the compounds of use in transition metal chemistry. Nevertheless, many of the latter are included in concert with their overall importance. 

Since the demonstration by Schumacher et al ) of the use of alkali metal vapor inclusion into a supersonic beam to produce clusters, there have been a number of attempts to generalize the approach. It has recently been recognized that instead of high temperature ovens, with their concommitant set of complex experimental problems, an intense pulsed laser beam focused on a target could be effectively used to produce metal atoms in the throat of a supersonic expansion valve. ) If these atoms are injected into a high pressure inert gas, such as helium, nucleation to produce clusters occurs. This development has as its most important result that clusters of virtually any material now can be produced and studied with relative ease. 

Only few investigations have been published on the gas-phase ion chemistry of host-guest complexes of calixarenes. With the advent of ESI mass spectrometry, especially when combined with ion-trap and FT-ICR mass spectrometry, this field has started to be developed. Binding selectivities of alkali metal ions to cahxarene-based crown ethers and open-chain ethers have been studied , the inclusion of neutral guests into the protonated resorcarene-based cavitand hosts by gas-phase ion-molecule reactions with amines have been studied and the formation of capsules from various calixarene tetraether derivatives and alkylammonium ions as ionic guests (notably enabling their detection by mass spectrometry) have been described recently . ... 

The limited solubility of starch and its modified products may affect the reversibility of many reactions. This may explain several, apparently unusual, reactions reported in starch chemistry. There are, for example, reports of starch esterification with sodium hydrogenphosphates, acylation of starch with acyl amides (which is equivalent to the transformation of an amide into an ester), and the formation of alkali-metal starchates upon treatment of starch with alkali (a reaction which fails for simple alcohols). A specific property of starch is its ability to form surface sorption and helical inclusion-complexes with many inorganic and organic guest molecules.4... 

For all preceding chalcogenide compounds prepared in supercritical amines, the metal centers are always monovalent. This includes both the alkali metal and the transition metal. In attempts to make more electronically interesting compounds, the inclusion of polyvdent metal ions with open shells in the chalcogenide framework was attempted. This was done by replacing the alkali metal cations with divalent cations or trivalent rare earth cations. However,... 

The finding of alkali metal hydroxide inclusions is important both from theoretical interest and from application. A possible consequence could be the isolation of alkali metal hydroxides from their aqueous solutions. Dried solid NaOH and KOH are made in industry by ordinary evaporation of their aqueous solutions obtained by electrolysis of NaCl and KCl, respectively. This method is uneconomical and wastes a lot of energy. On the contrary, the crystal inclusion method is very simple and economical Examples of such isolation processes are given below. 

Phenol-type hosts also form stable crystal inclusions with alkali metal hydroxides. For example, when a mixture of 7 (28.6 g 0.1 mol) and a 5 % LiOH aqueous solution... 

Alkali metal inclusion gives rise to very strongly basic zeolites, with strong electron donating power (Lewis bases). These are very active as basic catalysts, but their reactivity is too high to permit useful application. Where reducible cations are present in the framework such as in the titanosilicate, ETS-10, inclusion of sodium metal results in the reversible reduction of the framework... 

This chapter reviews the effect of alkali metal halogenides and zwitterionic form of glycine on the iodine-triiodide equilibrium in aqueous solution and the interaction of I2, and I3 with lithium halogenides (LiCl). It reveals and analyzes the results obtained by experimental studies using UV and IR spectroscopy, as well as the outcomes of theoretical investigations. Computational studies have been carried out using quantum-chemical methods of DFT-B3PW91/midi, explicit inclusion of solvent molecules, as well as by application of COSMO continuum model [30]. 

A review of nuclear magnetic properties of alkali metal nuclei is followed by a brief survey of solvation of alkali metal cations, their hydration especially. The chemistry of alkali metal anions is then evoked. Chemical shifts and relaxation rates will be described with emphasis on the predominant factors contributing to these observables. A brief history of alkali metal NMR will be followed by selected applications to ion pairing phenomena, inclusion complexes, preferential solvation, the chelate effect, and polyelectrolytes. 

The high temperatures of coal char oxidation lead to a partial vaporization of the mineral or ash inclusions. Compounds of the alkali metals, the alkaline earth metals, silicon, and iron are volatilized during char combustion. The volatilization of silicon, magnesium, calcium, and iron can be greatly enhanced by reduction of their refractory oxides to more volatile forms (e.g., metal suboxides or elemental metals) in the locally reducing environment of the coal particle. The volatilized suboxides and elemental metals are then reoxidized in the boundary layer around the burning particle, where they subsequently nucleate to form a submicron aerosol. 

Based on the concept of mixed-framework lattices, we have reported a novel class of hybrid solids that were discovered via salt-inclusion synthesis [4—7]. These new compounds exhibit composite frameworks of covalent and ionic lattices made of transition-metal oxides and alkali and alkaline-earth metal halides, respectively [4]. It has been demonstrated that the covalent frameworks can be tailored by changing the size and concentration of the incorporated salt. The interaction at the interface of these two chemically dissimilar lattices varies depending upon the relative strength of covalent vs. ionic interaction of the corresponding components. In some cases, the weak interaction facilitates an easy... 

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