Bases alkaline earth metals

Similarly, CALB has been used in combination with a palladium/alkaline earth metal-based racemization catalyst to effect a DKR on the benzylic amine 56e (Scheme 2.27). The (R)-amide 57e was obtained in very good yield and excellent optical purity. Several other substrates also underwent the reaction [29],... 

Group 4 metal based catalysts have been studied intensively in hydroamination reactions involving alkynes and allenes [77 81], but (achiral) hydroamination reac tions involving aminoalkenes were only recently reported [82 84]. The reactivity of these catalysts is significantly lower than that of rare earth, alkali, and alkaline earth metal based catalysts. In most instances, gem dialkyl activation [37] of the aminoalk ene substrate is required for catalytic turnover. 

We start with the observations of Kirchoff and Bunsen in Germany in 1859. They observed the bright line spectra for many alkali and alkaline-earth metal-based salts and are credited with the discovery of spectro-chemical analysis. The so-called principal atomic emission series for the common alkali metals is shown in Fig. 4.66. Note that these older atomic spectra are calibrated in terms of wave number, denoted by v, of the emitted radiation whose units are in reciprocal centimeters (denoted by cm ). 

Alkaline Earth Metal-Based Glasses/Interconnects Interface... 

F. 6 Selected alkaline earth-metal-based catalysis (DiPP = 2,6-diisopropylphenyl) [36,38,39, 107-111]... 

The development of group-4-metal-based catalysts for intramolecular hydro-amination of aUcenes has also led to several advanced systems for asymmetric hydroamination (Fig. 19). Most group 4 metal catalyst systems exhibit inferior reactivity and substrate scope (Table 19) in comparison to most rare earth metaland alkaline earth metal-based catalyst systems. They typically require high catalyst loadings and elevated reaction temperatures. However, the recent development of zwitterionic zirconium catalysts with significantly improved reactivities and selectivities [60, 118] promises to close this gap. 

Processes rendered obsolete by the propylene ammoxidation process (51) include the ethylene cyanohydrin process (52—54) practiced commercially by American Cyanamid and Union Carbide in the United States and by I. G. Farben in Germany. The process involved the production of ethylene cyanohydrin by the base-cataly2ed addition of HCN to ethylene oxide in the liquid phase at about 60°C. A typical base catalyst used in this step was diethylamine. This was followed by liquid-phase or vapor-phase dehydration of the cyanohydrin. The Hquid-phase dehydration was performed at about 200°C using alkah metal or alkaline earth metal salts of organic acids, primarily formates and magnesium carbonate. Vapor-phase dehydration was accomphshed over alumina at about 250°C. 

Difluoroethanol is prepared by the mercuric oxide cataly2ed hydrolysis of 2-bromo-l,l-difluoroethane with carboxyHc acid esters and alkaH metal hydroxides ia water (27). Its chemical reactions are similar to those of most alcohols. It can be oxidi2ed to difluoroacetic acid [381-73-7] (28) it forms alkoxides with alkaH and alkaline-earth metals (29) with alkoxides of other alcohols it forms mixed ethers such as 2,2-difluoroethyl methyl ether [461-57-4], bp 47°C, or 2,2-difluoroethyl ethyl ether [82907-09-3], bp 66°C (29). 2,2-Difluoroethyl difluoromethyl ether [32778-16-8], made from the alcohol and chlorodifluoromethane ia aqueous base, has been iavestigated as an inhalation anesthetic (30,31) as have several ethers made by addition of the alcohol to various fluoroalkenes (32,33). Methacrylate esters of the alcohol are useful as a sheathing material for polymers ia optical appHcations (34). The alcohol has also been reported to be useful as a working fluid ia heat pumps (35). The alcohol is available ia research quantities for ca 6/g (1992). 

Erythroidine behaves as a lactone and when one of its salts with an alkali or alkaline earth metal is catalytically hydrogenated under pressure, a mixture of dihydro-j3-erythroidines, with two tetrahydro- compounds is produced, from which dihydro- -erythroidine can be isolated as the hydrobromide. The dihydro- base has m.p. 85-6° (dec.), + 102-5° and... 

Zeolites are naturally occurring hydrous aluminum-sodium silicates in porous granule form. They are capable of exchanging their sodium base for calcium or magnesium and of expelling these alkaline earth metals for sodium by treatment with salt. Thus, they are a type of ion-exchange media. (Some zeolites act as molecular sieves by adsorption of water and polar compounds.)... 

Slag modifiers raise the fusion point or sintering temperature of the ash and directly neutralize any S03 formed. They are based on alkaline-earth metals such as magnesium, calcium, and strontium, or rare-earth metals such as cerium they are available as oxides, salts, or soaps. 

Krafft temperatures depend not only on chain length but on the cation. Eth-oxylation of the base alcohol reduces the Krafft temperature due to the higher solubility of the sulfate. Calcium and other earth alkaline metals produce an increase of the Krafft temperature that is significantly reduced by ethoxylation of the alcohol. The decrease is more significant for alkaline earth metals than for alkaline cations as shown in Table 6 [81,82], although it should be noted that, according to other workers, sodium dodecyl sulfate has a Krafft temperature of 16°C. 

Now consider strong and weak bases. The common strong bases are oxide ions and hydroxide ions, which are provided by the alkali metal and alkaline earth metal oxides and hydroxides, such as calcium oxide (see Table J.l). As we have seen,... 

A note on good practice The oxides and hydroxides of the alkali and alkaline earth metals are not Bronsted bases the oxide and hydroxide ions they contain are the bases (the cations are spectator ions). However, for convenience, chemists often refer to the compounds themselves as bases. 

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... 

Studies of CpLi solutions showed high conductivity, suggesting ionic particles in solution.91 Ionic particles could consist of the free ions, but anionic cyclopentadienides MCp2- particles isoelectronic to the well-known alkaline earth cyclopentadienides Cp2M (M = alkaline earth metal),103 could also be envisioned. Moreover, the structural motif of a sandwich complex where two Cp ligands bind to a metal center is well established throughout the periodic table. Indeed, the Cp2 Li anion was suggested based on NMR techniques,114-116 and... 

Based on donor atom type, macrocyclic ligands can be considered to span two extreme types. First there are those systems which chiefly contain nitrogen, sulfur, phosphorus, and/or arsenic donors. These macrocycles tend to have considerable affinity for transition and other heavy metal ions they usually show much less tendency to form stable complexes with ions of the alkali and alkaline earth metals. The present discussion will be restricted to a consideration of a selection of such ligands and their complexes. 

Atienza et al. [657] reviewed the applications of flow injection analysis coupled to spectrophotometry in the analysis of seawater. The method is based on the differing reaction rates of the metal complexes with 1,2-diaminocycl-ohexane-N, N, N, A/Metra-acetate at 25 °C. A slight excess of EDTA is added to the sample solution, the pH is adjusted to ensure complete formation of the complexes, and a large excess of 0.3 mM to 6 mM-Pb2+ in 0.5 M sodium acetate is then added. The rate of appearance of the Pbn-EDTA complex is followed spectrophotometrically, 3 to 6 stopped-flow reactions being run in succession. Because each of the alkaline-earth-metal complexes reacts at a different rate, variations of the time-scan indicates which ions are present. 

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