Metal salts, decomposition

The hydrogenation kinetics of cydohexene catalyzed by Pt2(dba)3 dispersed in BMI.PFg, BMI.BF4 and BMl,OTf are shown in Fig. 6.3. The kinetics curves were treated using the pseudo-elementary step and fitted (Eq. (6.1) by the following integrated rate equation for metal-salt decomposition (A —> B, hi) and autocatalytic nanoduster surface growth (A + B — 2B, 2). For a more detailed description of the use of the pseudo-elementary step for the treatment of hydrogenation kinetic data and derivation of the kinetic equations see elsewhere [81-83]. 

Alkyl hydroperoxides can be Hquids or soHds. Those having low molecular weight are soluble in water and are explosive in the pure state. As the molecular weight increases, ie, as the active oxygen content is reduced, water solubiUty and the violence of decomposition decrease. Alkyl hydroperoxides are stronger acids than the corresponding alcohols and have acidities similar to those of phenols, Alkyl hydroperoxides can be purified through their alkali metal salts (28). 

Alkyl hydroperoxides form stable alkaU metal salts with caustic however, when equimolar amounts of the hydroperoxide and its sodium salt are present in aqueous solution, rapid decomposition to tert-AcohoX and oxygen occurs (28). 

Decomposition Hazards. The main causes of unintended decompositions of organic peroxides are heat energy from heating sources and mechanical shock, eg, impact or friction. In addition, certain contaminants, ie, metal salts, amines, acids, and bases, initiate or accelerate organic peroxide decompositions at temperatures at which the peroxide is normally stable. These reactions also Hberate heat, thus further accelerating the decomposition. Commercial products often contain diluents that desensitize neat peroxides to these hazards. Commercial organic peroxide decompositions are low order deflagrations rather than detonations (279). 

Bina Selenides. Most biaary selenides are formed by beating selenium ia the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts ia aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH 2S [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the teUurides. Selenides of the alkah, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are iasoluble ia water. Polyselenides form when selenium reacts with alkah metals dissolved ia hquid ammonia. Metal (M) hydrogen selenides of the M HSe type are known. Some heavy-metal selenides show important and useful electric, photoelectric, photo-optical, and semiconductor properties. Ferroselenium and nickel selenide are made by sintering a mixture of selenium and metal powder. 

Complexing agents, which act as buffers to help control the pH and maintain control over the free metal—salt ions available to the solution and hence the ion concentration, include citric acid, sodium citrate, and sodium acetate potassium tartrate ammonium chloride. Stabilizers, which act as catalytic inhibitors that retard the spontaneous decomposition of the bath, include fluoride compounds thiourea, sodium cyanide, and urea. Stabilizers are typically not present in amounts exceeding 10 ppm. The pH of the bath is adjusted. 

The heavy metal salts, ia contrast to the alkah metal salts, have lower melting points and are more soluble ia organic solvents, eg, methylene chloride, chloroform, tetrahydrofiiran, and benzene. They are slightly soluble ia water, alcohol, ahphatic hydrocarbons, and ethyl ether (18). Their thermal decompositions have been extensively studied by dta and tga (thermal gravimetric analysis) methods. They decompose to the metal sulfides and gaseous products, which are primarily carbonyl sulfide and carbon disulfide ia varying ratios. In some cases, the dialkyl xanthate forms. Solvent extraction studies of a large number of elements as their xanthate salts have been reported (19). 

Meta.1 Sa.lt Forma.tion. At least three methods are commonly used to prepare metals salts. The fkst of these is known as the double decomposition method. 

Salt Formation. Citric acid forms mono-, di-, and tribasic salts with many cations such as alkahes, ammonia, and amines. Salts may be prepared by direct neutralization of a solution of citric acid in water using the appropriate base, or by double decomposition using a citrate salt and a soluble metal salt. 

Double Decomposition. In the double decomposition reaction, an inorganic metal salt such as a sulfate, chloride, acetate, or nitrate reacts with the sodium salt of the carboxyUc acid ia a hot aqueous solution. The metal soap precipitate is filtered, washed, dried, and milled. 

Azocarbonamide (I) Carbonamide N2, CO, CO2 190-230 220 Most widely used blowing agent in PVC and polyolefins. High decomposition temperature reduced by a variety of metal salts and oxides such as lead carbonate, lead phosphite and zinc oxide. High gas yield. Reaction products show little odour or discoloration. ... 

Alkyl hydroperoxides give alkoxy radicals and the hydroxyl radical. r-Butyl hydroperoxide is often used as a radical source. Detailed studies on the mechanism of the decomposition indicate that it is a more complicated process than simple unimolecular decomposition. The alkyl hydroperoxides are also sometimes used in conjunction with a transition-metal salt. Under these conditions, an alkoxy radical is produced, but the hydroxyl portion appears as hydroxide ion as the result of one-electron reduction by the metal ion. ... 

The decomposition of the nitrates produces oxygen molecules, and we have verified that if a mixture of silver nitrates and closed tubes is submitted to a thermal treatment (400°C) decomposing the salt, it is possible to observe filled CNTs (Ag, Co, Cu [34]). It appears that oxygen liberated during the thermal decomposition of the metal salt erodes the CNT tip and the yet un-decomposed salt then enters by capillarity (see Fig. 8). We have also observed during the electron-irradiation decomposition of enclosed nitrate that the liberated gases erodes the CNT cavity [22] (see the innermost tubes in Fig. 5). 

Slow thermal decomposition of the alkali metal salts of 3 takes place quantitatively in accordance with Eq. (5), where M represents an... 

Organic metal salts have frequently failed to produce an appreciable chemical stabilization effect, either during dehydrochlorination induction periods or in later decomposition stages. While this does not rule out the occurrence of Frye and Horst substitution reactions, it does suggest that these reactions may not be responsible for the observed retardation of color developments [126-128]. 

The decomposition of diacyl peroxides (36) is catalyzed by various transition metal salts,46,167 for example, Cu+ (Scheme 3.28).168,169 A side reaction is oxidation of alkyl radicals by the oxidized fonn of the metal salt e.g. Cu2+). 

Aqueous 50% hydrogen peroxide causes immediate blistering if allowed to come into contact with the skin. The presence of metal salts may cause decomposition of the hydrogen peroxide. 

Factors which Catalyze the Decomposition of Ammonium Perchlorate. Irradiation of AP with X-rays or gamma radiation causes it to decomp at a lower temp, presumably by the formn of holes or active sites in the cryst (Ref 36). Metal salts have been found to lower the decompn point of AP by as much as 80° (Ref 39), and to lower the induction period for its expln at 233° by 21 minutes (Ref 41). Inorg salts which have been found to catalyze the decompn of AP are listed below ... 

The kinetic behaviour of metal salts of oxyacids may be influenced by water of crystallization. Where complete-dehydration precedes decomposition, the anhydrous material is the product of a previous rate process and may have undergone recrystallization. If water is not effectively removed, there may at higher temperature be the transient formation of a melt prior to decomposition. The usual problems attend the identification of partial or transient liquefaction of the reactant in the mechanistic interpretation of kinetic data. 

It is convenient to classify here the decompositions of metal salts of the various oxyhalogen acids on the basis of the oxygen content of the anion, with subsections devoted to the metals of a particular sub-group of the Periodic Table. Again, consideration of the ammonium salts is deferred to Sect. 4. As noted elsewhere in this review, some reports are not explicit as to whether or not melting accompanies reaction thermal analysis studies can be valuable [843]. 

The grouping of ammonium salts in a separate section serves to emphasize the similarities of behaviour which are apparent in reactions yielding the volatile NH3 molecule, following removal of a proton from the NH4 cation. This property is not unique indeed, many cations are volatile and numerous salts leave no residue on completion of decomposition. Few kinetic investigations have, however, been reported for other compounds, in contrast to the extensive and detailed rate measurements which have been published for solid phase decompositions of many ammonium salts. Comparisons with the metal salts containing the same anion are sometimes productive, so that no single method of classification is altogether satisfactory. 

Metal salts of carboxylic acids obviously possess some organic character, but decompositions of these substances can be considered in the present context. Many metal carboxylates decompose at a reactant—product interface and their nucleation and growth processes are similar to the behav-... 

The nature of the highly dispersed oxides obtainable from the decomposition of metal salts of hydroxypolycarboxylic acids has been discussed by Marcilly et al. [285]. 

Summary qf kinetic results for the decomposition of metal salts of aromatic carboxylic acids [88,460,1109,1110]... 

Neutral organophosphorus chalcogenide-metal salt interactions addition and decomposition products. N. M. Karayannis, C. M. Mikulski and L. L. Pytlewski, Inorg. Chim. Acta, Rev., 1971, 5, 69-105 (479). 

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