Alkaline earths, reactions

Although adiabatic correlation arguments [10] could, in principle, be used to understand the observed spin-orbit effects, such considerations have been shown [119-123] to be poor predictors for the product electronic state branching in chemiluminescent alkaline earth reactions. Because of the relatively low ionization potentials of the excited alkaline earth atoms, their reactions proceed by charge transfer to an ionic surface [116]. As the reactants approach but before charge... 

Historically an earth was a non-metallic substance, nearly insoluble in water and unchanged on heating. The alkaline earth oxides, e.g. CaO, have an alkaline reaction in addition to being clearly earths . 

Salt Formation. Salt-forming reactions of adipic acid are those typical of carboxylic acids. Alkali metal salts and ammonium salts are water soluble alkaline earth metal salts have limited solubiUty (see Table 5). Salt formation with amines and diamines is discussed in the next section. 

Pentaerythritol is produced by reaction of formaldehyde [50-00-0] and acetaldehyde [75-07-0] in the presence of a basic catalyst, generally an alkah or alkaline-earth hydroxide. Reaction proceeds by aldol addition to the carbon adjacent to the hydroxyl on the acetaldehyde. The pentaerythrose [3818-32-4] so produced is converted to pentaerythritol by a crossed Cannizzaro reaction using formaldehyde. All reaction steps are reversible except the last, which allows completion of the reaction and high yield industrial production. 

Arsenic pentafluoride can be prepared by reaction of fluorine and arsenic trifluoride or arsenic from the reaction of NF O and As (16) from the reaction of Ca(FS02)2 and H AsO (17) or by reaction of alkaH metal or alkaline-earth metal fluorides or fluorosulfonates with H AsO or H2ASO2F (18). 

Hexafluoroarsenic acid [17068-85-8] can be prepared by the reaction of arsenic acid with hydrofluoric acid or calcium fluorosulfate (29) and with alkaH or alkaline-earth metal fluorides or fluorosulfonates (18). The hexafluoroarsenates can be prepared directly from arsenates and hydrofluoric acid, or by neutrali2ation of HAsF. The reaction of 48% HF with potassium dihydrogen arsenate(V), KH2ASO4, gives potassium hydroxypentafluoroarsenate(V)... 

Chemical Properties. In addition to the reactions Hsted in Table 3, boron trifluoride reacts with alkali or alkaline-earth metal oxides, as well as other inorganic alkaline materials, at 450°C to yield the trimer trifluoroboroxine [13703-95-2] (BOF), MBF, and MF (29) where M is a univalent metal ion. The trimer is stable below — 135°C but disproportionates to B2O2 and BF at higher temperatures (30). 

Properties. Lithium fluoride [7789-24-4] LiF, is a white nonhygroscopic crystaUine material that does not form a hydrate. The properties of lithium fluoride are similar to the aLkaline-earth fluorides. The solubility in water is quite low and chemical reactivity is low, similar to that of calcium fluoride and magnesium fluoride. Several chemical and physical properties of lithium fluoride are listed in Table 1. At high temperatures, lithium fluoride hydroly2es to hydrogen fluoride when heated in the presence of moisture. A bifluoride [12159-92-17, LiF HF, which forms on reaction of LiF with hydrofluoric acid, is unstable to loss of HF in the solid form. 

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). 

Ultimately, as the stabilization reactions continue, the metallic salts or soaps are depleted and the by-product metal chlorides result. These metal chlorides are potential Lewis acid catalysts and can greatiy accelerate the undesired dehydrochlorination of PVC. Both zinc chloride and cadmium chloride are particularly strong Lewis acids compared to the weakly acidic organotin chlorides and lead chlorides. This significant complication is effectively dealt with in commercial practice by the co-addition of alkaline-earth soaps or salts, such as calcium stearate or barium stearate, ie, by the use of mixed metal stabilizers. 

The ionic hydrazides are extremely sensitive and explode on contact with ak or upon heating. The alkaline-earth hydrazides, which have the general formula M(N2H2), appear to be less sensitive (15). Hydrazides such as aluminum hydrazide [25546-96-7] Al(N2H2)3, have also been made (16). The hydrazide anion is more nucleophilic than hydrazine and undergoes reactions not possible using hydrazine itself (17). Thus, styrene in ethyl ether solution at 0°C is... 

Acetyhdes of the alkaU and alkaline-earth metals are formed by reaction of acetylene with the metal amide in anhydrous Hquid ammonia. 

The reaction of chlorine gas with a mixture of ore and carbon at 500—1000°C yields volatile chlorides of niobium and other metals. These can be separated by fractional condensation (21—23). This method, used on columbites, is less suited to the chlorination of pyrochlore because of the formation of nonvolatile alkaU and alkaline-earth chlorides which remain in the reaction 2one as a residue. The chlorination of ferroniobium, however, is used commercially. The product mixture of niobium pentachloride, iron chlorides, and chlorides of other impurities is passed through a heated column of sodium chloride pellets at 400°C to remove iron and aluminum by formation of a low melting eutectic compound which drains from the bottom of the column. The niobium pentachloride passes through the column and is selectively condensed the more volatile chlorides pass through the condenser in the off-gas. The niobium pentachloride then can be processed further. 

Basic oxides of metals such as Co, Mn, Fe, and Cu catalyze the decomposition of chlorate by lowering the decomposition temperature. Consequendy, less fuel is needed and the reaction continues at a lower temperature. Cobalt metal, which forms the basic oxide in situ, lowers the decomposition of pure sodium chlorate from 478 to 280°C while serving as fuel (6,7). Composition of a cobalt-fueled system, compared with an iron-fueled system, is 90 wt % NaClO, 4 wt % Co, and 6 wt % glass fiber vs 86% NaClO, 4% Fe, 6% glass fiber, and 4% BaO. Initiation of the former is at 270°C, compared to 370°C for the iron-fueled candle. Cobalt hydroxide produces a more pronounced lowering of the decomposition temperature than the metal alone, although the water produced by decomposition of the hydroxide to form the oxide is thought to increase chlorine contaminate levels. Alkaline earths and transition-metal ferrates also have catalytic activity and improve chlorine retention (8). 

The stability of the alkali metal ozonides increases from Li to Cs alkaline-earth ozonides exhibit a similar stability pattern. Reaction of metal ozonides with water proceeds through the intermediate formation of hydroxyl radicals. 

Alkali Meta.IPhospha.tes, A significant proportion of the phosphoric acid consumed in the manufacture of industrial, food, and pharmaceutical phosphates in the United States is used for the production of sodium salts. Alkali metal orthophosphates generally exhibit congment solubility and are therefore usually manufactured by either crystallisation from solution or drying of the entire reaction mass. Alkaline-earth and other phosphate salts of polyvalent cations typically exhibit incongment solubility and are prepared either by precipitation from solution having a metal oxide/P20 ratio considerably lower than that of the product, or by drying a solution or slurry with the proper metal oxide/P20 ratio. 

The use of alkali or alkaline-earth sulfides cataly2es the reaction so that it is complete in a few hours at 150—160°C use of aluminum chloride as the catalyst gives a comparable reaction rate at 115°C. When an excess of sulfur is used, the product can be distilled out of the reactor, and the residue of sulfur forms part of the charge in the following batch reaction. The reaction is carried out in a stainless steel autoclave, and the yield is better than 98% based on either reactant. Phosphoms sulfochloride is used primarily in the manufacture of insecticides (53—55), such as Parathion. 

The alkah metal phosphides of formula M P and the alkaline-earth phosphides of formula M2P2 contain the P anion. Calcium diphosphide [81103-86-8] CaP2, contains P reaction with water Hberates diphosphine and maintains the P—P linkage. 

Lewis acids, such as the haUde salts of the alkaline-earth metals, Cu(I), Cu(II), 2inc, Fe(III), aluminum, etc, are effective catalysts for this reaction (63). The ammonolysis of polyamides obtained from post-consumer waste has been used to cleave the polymer chain as the first step in a recycle process in which mixtures of nylon-6,6 and nylon-6 can be reconverted to diamine (64). The advantage of this approach Hes in the fact that both the adipamide [628-94-4] and 6-aminohexanoamide can be converted to hexarnethylenediarnine via their respective nitriles in a conventional two-step process in the presence of the diamine formed in the original ammonolysis reaction, thus avoiding a difficult and cosdy separation process. In addition, the mixture of nylon-6,6 and nylon-6 appears to react faster than does either polyamide alone. 

The aramids are formed in the low temperature reaction, -10 to 60°C, of equimolar amounts of the diacid chloride and the diamine in an amide solvent, typically dimethyl acetamide (DMAc) or A/-meth5i-2-pyrrohdinone (NMP) and usually with a small amount of an alkaU or alkaline-earth hydroxide and a metal salt, such as LiOH [1310-65-2] LiCl, Ca(OH)2 [1305-62-0] or CaCl2 added to increase the solubiUty of the polymer and neutralize the hydrochloric acid generated in the reaction. 

The speed of the reaction depends both on the metal and on the alcohol, increasing as electropositivity iacreases and decreasiag with length and branching of the chain. Thus sodium reacts strongly with ethanol, but slowly with tertiary butyl alcohol. The reaction with alkaU metals is sometimes carried out ia ether, ben2ene, or xylene. Some processes use the metal amalgam or hydride iastead of the free metal. Alkaline earth metals and aluminum are often covered with an oxide film which hinders the reaction. 

The acidic character of siUca is shown by its reaction with a large number of basic oxides to form siUcates. The phase relations of numerous oxide systems involving siUca have been summarized (23). Reactions of siUca at elevated temperatures with alkaU and alkaline-earth carbonates result in the displacement of the more volatile acid, CO2, and the formation of the corresponding siUcates. Similar reactions occur with a number of nitrates and sulfates. Sihca at high temperature in the presence of sulfides gives thiosiUcates or siUcon disulfide, SiS2. 

Fused basic salts and basic oxides react with vitreous siUca at elevated temperatures. Reaction with alkaline-earth oxides takes place at approximately 900°C. Hahdes tend to dissolve vitreous siUca at high temperatures fluorides are the most reactive (95). Dry halogen gases do not react with vitreous siUca below 300°C. Hydrogen fluoride, however, readily attacks vitreous siUca. 

Sulfur combines directly with hydrogen at 150—200°C to form hydrogen sulfide. Molten sulfur reacts with hydrogen to form hydrogen polysulfides. At red heat, sulfur and carbon unite to form carbon disulfide. This is a commercially important reaction in Europe, although natural gas is used to produce carbon disulfide in the United States. In aqueous solutions of alkaU carbonates and alkaU and alkaline-earth hydroxides, sulfur reacts to form sulfides, polysulfides, thiosulfates, and sulfites. 

Other. Insoluble alkaline-earth metal and heavy metal stannates are prepared by the metathetic reaction of a soluble salt of the metal with a soluble alkah—metal stannate. They are used as additives to ceramic dielectric bodies (32). The use of bismuth stannate [12777-45-6] Bi2(Sn02)3 5H20, with barium titanate produces a ceramic capacitor body of uniform dielectric constant over a substantial temperature range (33). Ceramic and dielectric properties of individual stannates are given in Reference 34. Other typical commercially available stannates are barium stannate [12009-18-6] BaSnO calcium stannate [12013 6-6] CaSnO magnesium stannate [12032-29-0], MgSnO and strontium stannate [12143-34-9], SrSnO. ... 

Composite Oxyalkoxides. Composite oxyalkoxides can be prepared by reaction of tetraalkyl titanates and alkaline-earth metal hydroxides. These oxyalkoxides and their derivatives can be hydroly2ed and thermally decomposed to give alkaline-earth metal titanates such as barium titanate (150). 

Barium is a member of the aLkaline-earth group of elements in Group 2 (IIA) of the period table. Calcium [7440-70-2], Ca, strontium [7440-24-6], Sr, and barium form a closely aUied series in which the chemical and physical properties of the elements and thek compounds vary systematically with increa sing size, the ionic and electropositive nature being greatest for barium (see Calcium AND CALCIUM ALLOYS Calcium compounds Strontium and STRONTIUM compounds). As size increases, hydration tendencies of the crystalline salts increase solubiUties of sulfates, nitrates, chlorides, etc, decrease (except duorides) solubiUties of haUdes in ethanol decrease thermal stabiUties of carbonates, nitrates, and peroxides increase and the rates of reaction of the metals with hydrogen increase. 

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