Alkaline earth metals reaction with water

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). 

With the exception of beryllium, the alkaline earth elements react with water to yield metal hydroxides, M(OH)2. Magnesium undergoes reaction only at temperatures above 100°C calcium and strontium react slowly with liquid water at room temperature. Only barium reacts vigorously. 

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. 

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. 

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. 

BeryUium reacts with fused alkaU haUdes releasing the alkaU metal until an equUibrium is estabUshed. It does not react with fused haUdes of the alkaline-earth metals to release the alkaline-earth metal. Water-insoluble fluoroberyUates, however, are formed in a fused-salt system whenever barium or calcium fluoride is present. BeryUium reduces haUdes of aluminum and heavier elements. Alkaline-earth metals can be used effectively to reduce beryUium from its haUdes, but the use of alkaline-earths other than magnesium [7439-95-4] is economically unattractive because of the formation of water-insoluble fluoroberyUates. Formation of these fluorides precludes efficient recovery of the unreduced beryUium from the reaction products in subsequent processing operations. 

Hydrogen can be prepared by the reaction of water or dilute acids on electropositive metals such as the alkali metals, alkaline earth metals, the metals of Groups 3, 4 and the lanthanoids. The reaction can be explosively violent. Convenient laboratory methods employ sodium amalgam or calcium with water, or zinc with hydrochloric acid. The reaction of aluminium or ferrosilicon with aqueous sodium hydroxide has also been used. For small-scale preparations the hydrolysis of metal hydrides is convenient, and this generates twice the amount of hydrogen as contained in the hydride, e.g. ... 

Section 20.1 deals with the processes by which these metals are obtained from their principal ores. Section 20.2 describes the reactions of the alkali and alkaline earth metals, particularly those with hydrogen, oxygen, and water. Section 20.3 considers the redox chemistry of the transition metals, their cations (e.g., Fe2+, Fe3+), and their oxoanions (e.g., Cr042-). ... 

The compounds formed by the reaction of hydrogen with the alkali and alkaline earth metals contain H- ions for example, sodium hydride consists of Na+ and H- ions. These white crystalline solids are often referred to as saline hydrides because of their physical resemblance to NaCL Chemically, they behave quite differently from sodium chloride for example, they react with water to produce hydrogen gas. Typical reactions are... 

Alkaline earth metal A metal in Group 2 of file periodic table, 31 hydrogen reactions with, 542 oxygen reactions with, 543-544 reactions, 54U, 552q water reactions with, 542... 

Foreign cations can increasingly lower the yield in the order Fe, Co " < Ca " < Mn < Pb " [22]. This is possibly due to the formation of oxide layers at the anode [42], Alkali and alkaline earth metal ions, alkylammonium ions and also zinc or nickel cations do not effect the Kolbe reaction [40] and are therefore the counterions of choice in preparative applications. Methanol is the best suited solvent for Kolbe electrolysis [7, 43]. Its oxidation is extensively inhibited by the formation of the carboxylate layer. The following electrolytes with methanol as solvent have been used MeOH-sodium carboxylate [44], MeOH—MeONa [45, 46], MeOH—NaOH [47], MeOH—EtsN-pyridine [48]. The yield of the Kolbe dimer decreases in media that contain more than 4% water. 

That eh is the intermediate species and not the H atom has been verified by adding NzO and methanol to water then, N2, not H2, is the principal product. Alkali and alkaline earth metals above Na in the electrochemical series will also generate eh on dissolution in water. Moreover the H/D isotope effect in water containing 50% D is consistent with the reaction 2eh—H2 + 20H (Anbar and Meyerstein, 1966 Hart and Anbar, 1970). 

The collected papers of a symposium at Dallas, April 1956, cover all aspects of the handling, use and hazards of lithium, sodium, potassium, their alloys, oxides and hydrides, in 19 chapters [1], Interaction of all 5 alkali metals with water under various circumstances has been discussed comparatively [2], In a monograph covering properties, preparation, handling and applications of the enhanced reactivity of metals dispersed finely in hydrocarbon diluents, the hazardous nature of potassium dispersions, and especially of rubidium and caesium dispersions is stressed [3], Alkaline-earth metal dispersions are of relatively low hazard. Safety practices for small-scale storage, handling, heating and reactions of lithium potassium and sodium with water are reviewed [4],... 

Water, in its reaction with the alkali- and alkaline-earth metals, resembles ammonia, but the complexes with the halides of the platinum metals are different. The water molecule has two lone pairs of electrons, but these pairs seem to be less active in complex formation. There are many cases in which from the magnetic moment it can be concluded that the hydrates are still ionic, whereas in the corresponding NH3 complex there is covalency, the NH3 molecules sharing their lone electron-pairs with the metal atom. 

Table 2 gives thermoehemica data of alkaline-earth metal hydrides. All form orthorhombic crystals. Calcium hydride is a convenient portable source of hydrogen gas, which results from its reaction with water. 

Quinalizarin reagent blue precipitate or cornflower-blue colouration with magnesium salts. The colouration can be readily distinguished from the blue-violet colour of the reagent. Upon the addition of a little bromine water, the colour disappears (difference from beryllium). The alkaline earth metals and aluminium do not interfere under the conditions of the test, but all elements of Groups I to III should be removed. Phosphates and large amounts of ammonium salts decrease the sensitivity of the reaction. 

The complexes Mg(N03)2 terpy 2H20, Ca(SCN)2 2terpy H20, and Ba(SCN)2 terpyH20 have been reported, but are of unknown structure (455). ESR studies of the terpy radical anion obtained from the reaction of terpy with alkaline earth metals (Mg, Ca, Sr, or Ba) have indicated that a significant interaction occurs between the anion and the cation (79). Spectrophotometric measurements have indicated that magnesium sulfate forms a 1 1 complex with terpy in water, with K = 5.858 + 0.023 mol (185,186). 

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