Hydroxides alkali metals

Addition of an alkali metal hydroxide solution to an aqueous solution of a nickel(II) salt precipitates a finely-divided green powder. nickel(II) hydroxide NilOHfj on heating this gives the black oxide. NiO. which is also obtained by heating nickel(II) carbonate or the hydrated nitrate. Black nickel(II) sulphide, NiS, is obtained by passing hydrogen sulphide into a solution of a nickel(II) salt. 

Strong and Weak Bases Just as the acidity of an aqueous solution is a measure of the concentration of the hydronium ion, H3O+, the basicity of an aqueous solution is a measure of the concentration of the hydroxide ion, OH . The most common example of a strong base is an alkali metal hydroxide, such as sodium hydroxide, which completely dissociates to produce the hydroxide ion. 

The catalysts most often described in the literature (209—211,252) are sodium or potassium hydroxide, methoxide, or ethoxide. The reported ratio of alkali metal hydroxides or metal alcoholates to that of poly(vinyl acetate) needed for conversion ranges from 0.2 to 4.0 wt % (211). Acid catalysts ate normally strong mineral acids such as sulfuric or hydrochloric acid (252—254). Acid-cataly2ed hydrolysis is much slower than that of the alkaline-cataly2ed hydrolysis, a fact that has limited the commercial use of these catalysts. 

Alkali Metal Hydroxides. Addition of base to aqueous chloroformates cataly2es hydrolysis to yield the parent hydroxy compound (11). However, the use of a stoichiometric amount of alkaU metal hydroxides can lead to the symmetrical carbonate, especially from aryl chloroformates (12,13). 

In the presence of an alkali metal hydroxide at about 50°C, chloroform condenses with acetone to give l,l,l-trichloro-2-methyl-2-propanol, [57-15-8] ie, chlorobutanol, chloretone, or acetone—chloroform (9,10). Chlorobutanol is a white crystalline substance with a campborlike odor its sedative, anesthetic, and antiseptic properties have given the compound some importance in the pharmaceutical industry. 

The alkali metal hydroxides are also readily absorb CO2 and H2S to form carbonates (or hydrogencarbonates) and sulfides (or hydrogen-sulfides), and are extensively used to remove mercaptans from petroleum products. Amphoteric oxides such as those of Al, Zn, Sn and Pb react with MOH to form aluminates, zincates, stannates and plumbates, and even SiC>2 (and silicate glasses) are attacked. 

With alkali metal hydroxides, both N2O and N2 are formed in addition to the nitrite ... 

Fusion of MnOa with an alkali metal hydroxide and an oxidizing agent such as KNO3 produces very dark-green manganate(VI) salts (manganates) which are stable in strongly alkaline solution but which disproportionate readily in neutral or acid solution (see Fig. 24.1) ... 

The alkali metal hydroxides, instead of the alkali metals per se, can be employed to produce the alkali metal 2,2,2-trifluoroethanolate. However, this introduces water in the reaction mixture which requires removal prior to vinylation with acetylene. The crude products, on further distillation, yielded 2,2,2-trifluoroethyl vinyl ether having a boiling point of 43.1°C at 759 mm. 

I) Refluxing said benzyl ester with an aqueous alcoholic alkali metal hydroxide solution to saponify the benzyl ester group, neutralizing the saponification mixture by the addition of hydrochloric acid, extracting the neutralized mixture with chloroform, and separating the resulting (S,N-ditrityl-L-cysteinyl)-L-proline. 

Under the influence of thermal motion and on endothermic electron transition from the OH ion to the Me ion in alkali metal hydroxides the formation of the Me. and OH. radicals takes place. As a result, free va-... 

Different efficiency of alkali metal hydroxides seems to be associated with differing ionization potentials. 

The inhibitive efficiency of alkali metal hydroxides increases with increased branching of polyethylene. This is confirmed by more pronounced effect of these hydroxides diminishing the yield of propane and propylene than in case of ethane and ethylene. The decreased yield of propane and propylene is also conditioned by more efficient inhibition of the macroradical isomerization stage by alkali metal hydroxides. Upon thermal destruction of polyethylene with the use of inhibitors the... 

A three-step process developed hy Snamprogetti is based on the reaction of acetylene and acetone in liquid ammonia in the presence of an alkali metal hydroxide. The product, methylhutynol, is then hydrogenated to methylhutenol followed hy dehydration at 250-300°C over an acidic heterogeneous catalyst. 

Also, nylon-6 waste may be hydrolyzed in the presence of an aqueous alkali metal hydroxide or acid5 to produce an alkali metal or acid salt of 6-aminocaproic acid (ACA). The reaction of nylon-6 waste with dilute hydrochloric acid is rapid at 90- 100°C. The reaction mixture is poured into water to form a dilute aqueous solution of the ACA salt. Filtration is used to remove undissolved impurities such as pigments, additives, and fillers followed by treatment of the acid solution with a strong cation exchange resin. A sulfonic acid cationic exchanger absorbs ACA salt and pure ACA is eluted with ammonium hydroxide to form a dilute aqueous solution. Pure ACA is obtained by crystallization of die solution. 

The Ford hydroglycolysis process is an example of a combined approach for die depolymerization of PURs. In a reactor, polyurethane foam is reacted with a mixture of water, diethylene glycol, and alkali metal hydroxides at high temperature to form polyols. When sodium hydroxide is added as a catalyst, a cleaner polyol is formed because all of the carbamates and ureas in the product are converted into amines and alcohols by hydrolysis.33... 

When ethoxylated nonylphenol and polyethylene glycol is treated with a mixture of H2S04 and H3P04 and neutralized with an alkali metal hydroxide or amine, surfactants containing sulfate esters and phosphate esters are obtained which cause little corrosion of metals such as surfaces of laundering equipments and automobiles [55]. 

An interesting feature of the ring opening polymerization of siloxanes is their ability to proceed via either anionic or cationic mechanisms depending on the type of the catalyst employed. In the anionic polymerization alkali metal hydroxides, quaternary ammonium (I NOH) and phosphonium (R POH) bases and siloxanolates (Si—Oe M ) are the most widely used catalysts 1,2-4). They are usually employed at a level of 10 2 to KT4 weight percent depending on their activities and the reaction conditions. The activity of alkali metal hydroxides and siloxanolates decrease in the following order 76 79,126). 

By using an alkali-metal hydroxide in situ as a proton acceptor, the alkali-metal dithiocarbamate salts, having various degrees of hydration, may be obtained (17). 

Licht et al. [17] developed a method of numerical analysis to describe the above-quoted equilibria of the 11 participating species (including alkali metal cations) in aqueous polysulfide solution, upon simple input to the algorithm of the temperature and initial concentration of sulfur, alkali metal hydroxide, and alkali metal hydrosulfide in solution. The equilibria constants were evaluated by compensation of the polysulfide absorption spectrum for the effects of H8 absorption and by computer analysis of the resultant spectra. Results from these calculations were used to demonstrate that the electrolyte is unstable, and that gradual degradation of polysulfide-based PECs (in the long term) can be attributed to this factor (Chap. 5). 

Solid super bases, prepared by successive treatment of y-alumina with alkali metal hydroxide and alkali metal, are highly active catalysts for reactions involving reactive carbanions, and have been commercialised by Sumitomo (Suzukamo et al, 1997). For example, t.vobutylbenzene, the. starting material for ibuprofen (see earlier) is produced by side-chain alkylation of toluene with propylene over a K/KOH/AI2O3 catalyst (Eqn. (14)). 

Typically, one or more reactants are organic liquids or solids dissolved in a nonpolar organic solvent (RX in Fig. 3.56), while the other reactants are salts or alkali metal hydroxides in aqueous solution (NaY in Fig. 3.56). 

Although organosilanes appear to react slowly (if at all) with water alone, in the presence of acids or bases (e.g., alkali metal hydroxides), reactions to give a silanol and H2 are rapid, with bases being particularly powerful catalysts. The evolution of H2 in this type of reaction may be used as both a qualitative and a quantitative test for Si-H bonds, and the mechanism of the acid and the base hydrolysis has been discussed in detail (30,31). This hydrolytic method is not very common for the preparation of silanols that are to be isolated, because both acids and bases catalyze the condensation of silanols to siloxanes, and therefore, only compounds containing large substituents are conveniently made in this way. If an anhydrous alkali metal salt is used, a metal siloxide may be isolated and subsequently hydrolyzed to give the silanol [Eq. (10)] (32). 

Next, a series of runs was conducted to determine the effect of various alkali metal hydroxide additions along with the sponge nickel catalyst. The 50 wt. % sodium hydroxide and 50 wt. % potassium hydroxide caustic solution used in the initial test was replaced with an aqueous solution of the alkali metal hydroxide at the level indicated in Table 2. After the reaction number of cycles indicated in Table 2, a sample was removed for analysis. The conditions and results are shown in Table 2. The results reported in Table 2 show the level of 2° Amine in the product from the final cycle. The level of NPA in all of the mns was comparable to the level observed in the initial test. No significant levels of other impurities were detected. 

Tables 1 and 2 clearly show that the use of such alkali metal hydroxides as KOH, CsOH, and mixtures of KOH/NaOH allowed the reaction to proceed to a high DMAPN conversion with a very high selectivity for the primary amine. These results suggest that the highest selectivity in the hydrogenation of DMAPN to DMAPA is obtained with KOH, and mixtures of KOH/NaOH.

Table 2 Effect of alkali metal hydroxide on activity and selectivity.

Run Alkali Metal Hydroxide Metal Hydroxide Quantity Temperature (°C) Pressure (PSIG) Number of Cycles 2° Amine (ppm)... 

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