Alkali hydroxides, reactions aqueous solutions

The synthesis mixtures were prepared using tetraethylammonium hydroxide (40 % aqueous solution, Alfa or 35 % aqueous solution, Aldrich) with a very low alkali cations content (Na<2ppm, K<0.5ppm), deionized water, tetraethylorthotitanate (TEOT) or tetrabutylorthotitanate (TBOT) as a source of Ti and amorphous silica (Aerosil 200, Degussa) or tetraethylorthosilicate (TEOS, Aldrich) as the source of silica. Depending on the synthesis method a source of aluminium can be directly added to the synthesis mixture (metal Al, aluminium halide, etc.) or incorporated in the seeds of aluminosilicate zeolite Beta. Four synthetic procedures were developed and Table 1 summarizes the typical ranges of chemical composition of the initial mixture and the typical results of the syntheses. The methods are denoted according to the nature of the silica source and, in one case, the use of seeds. The preparation of the reaction mixtures was as follows ... 

Phosphonium ylides are typically prepared by the reaction of a phosphonium salt with a base. Non-stabilized ylides require a strong base (such as BuLi) under inert conditions, while stabilized ylides require a weaker base (for example, alkali metal hydroxides in aqueous solution). For more detail on the variety of bases and reaction conditions that can be used in the Wittig reaction, see references [2] and [5],... 

MetaUic ions are precipitated as their hydroxides from aqueous caustic solutions. The reactions of importance in chlor—alkali operations are removal of magnesium as Mg(OH)2 during primary purification and of other impurities for pollution control. Organic acids react with NaOH to form soluble salts. Saponification of esters to form the organic acid salt and an alcohol and internal coupling reactions involve NaOH, as exemplified by reaction with triglycerides to form soap and glycerol,... 

Barium titanate thin films can be deposited on various substances by treating with an aqueous solution containing barium salts and an alkanolamine-modifted titanate such as TYZOR TE (151). In a similar fashion, reaction of a tetraalkyl titanate with an alkah metal hydroxide, such as potassium hydroxide, gives oxyalkoxide derivatives (KTi O(OR) ), which can be further processed to give alkali metal titanate powders, films, and fibers (152—155). The fibers can be used as adsorbents for radioactive metals such as cesium, strontium, and uranium (156). 

In a 2-1. flask provided with a mechanical stirrer, separatory funnel, and thermometer, are placed 189 g. (2 moles) of chloro-acetic acid and 150 cc. of water. The flask is cooled in ice water, and a cold solution of 160 g. (4 moles) of sodium hydroxide in 500 cc. of water is added, with stirring, at such a rate that the temperature does not exceed 30° (Note 1). AfLer all the alkali has been added, the cooling bath is removed, and an aqueous solution (Note 2) containing 31 g. (1 mole) of methylamine is added slowly. The reaction is exothermic, and the temperature is kept below 50° by occasional immersion of the flask in ice water. After all the methylamine has been added, the solution is allowed to stand for two hours to complete the reaction. 

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. 

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. 

Urea-formaldehyde resins are generally prepared by condensation in aqueous basic medium. Depending on the intended application, a 50-100% excess of formaldehyde is used. All bases are suitable as catalysts provided they are partially soluble in water. The most commonly used catalysts are the alkali hydroxides. The pH value of the alkaline solution should not exceed 8-9, on account of the possible Cannizzaro reaction of formaldehyde. Since the alkalinity of the solution drops in the course of the reaction, it is necessary either to use a buffer solution or to keep the pH constant by repeated additions of aqueous alkali hydroxide. Under these conditions the reaction time is about 10-20 min at 50-60 C. The course of the condensation can be monitored by titration of the unused formaldehyde with sodium hydrogen sulfite or hydroxylamine hydrochloride. These determinations must, however, be carried out quickly and at as low temperature as possible (10-15 °C), otherwise elimination of formaldehyde from the hydroxymethyl compounds already formed can falsify the analysis. The isolation of the soluble condensation products is not possible without special precautions, on account of the facile back-reaction it can be done by pumping off the water in vacuum below 60 °C imder weakly alkaline conditions, or better by careful freeze-drying. However, the further condensation to crosslinked products is nearly always performed with the original aqueous solution. 

Rubidium acid salts are usually prepared from rubidium carbonate or hydroxide and the appropriate acid in aqueous solution, followed by precipitation of the crystals or evaporation to dryness. Rubidium sulfate is also prepared by the addition of a hot solution of barium hydroxide to a boiling solution of rubidium alum until all the aluminum is precipitated. The pH of the solution is 7.6 when the reaction is complete. Aluminum hydroxide and barium sulfate are removed by filtration, and rubidium sulfate is obtained by concentration and crystallization from the filtrate. Rubidium aluminum sulfate dodecahydrate [7488-54-2] (alum), RbA SO 12H20, is formed by sulfuric acid leaching of lepidolite ore. Rubidium alum is more soluble than cesium alum and less soluble than the other alkali alums. Fractional crystallization of Rb alum removes K, Na, and Li values, but concentrates the cesium value. Rubidium hydroxide, RbOH, is prepared by the reaction of rubidium sulfate and barium hydroxide in solution. The insoluble barium sulfate is removed by filtration. The solution of rubidium hydroxide can be evaporated partially in pure nickel or silver containers. Rubidium hydroxide is usually supplied as a 50% aqueous solution. Rubidium carbonate, Rb2C03, is readily formed by bubbling carbon dioxide through a solution of rubidium hydroxide, followed by evaporation to dryness in a fluorocarbon container. Other rubidium compounds can be formed in the laboratory by means of anion-exchange techniques. Table 4 lists some properties of common rubidium compounds. 

This reaction is highly exothermic. If the heat of the reaction is not conducted thru the walls of a closed container at a rate capable of maintaining an equilibrium temperature, an increase in pressure results with an increase in reaction rate, leading to explosive conditions. Acid salts, such as stannic chloride and zinc chloride, and bases, such as alkali metal hydroxides, either solid or in aqueous solution, and tertiary amines are all effective catalysts. It is, therefore, imperative that the concentration of such contaminants be kept at a minimum when transporting or storing sizeable quantities of ethylene oxide Accdg to Hess Tilton (Ref 16), a 90% decompn takes place if 100% vapor of EtnO in a closed container is. initiated with MF. There is no upper limit of EtnO in air (the previously reported value of 80% was in error), but the lower expl limit is 3% (Ref 17, p 87)... 

Sulfur combines direcdy 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 alkali carbonates and alkali and alkaline-earth hydroxides, sulfur reacts to form sulfides, polysulfides, thiosulfates, and sulfites. 

The concentration of alkali required depends on the properties of the radicals R and R1. The more electrophilic the radicals and the more dcidic the nitramine, the easier the course of reaction. Secondary nitramines are decomposed by an aqueous solution of sodium hydroxide. The reaction conditions, including the concentrations of NaOH solutions differ according to the substance. Van Erp and Franchimont [21] found that the reaction proceeded by the following mechanism ... 

The electrochemical oxidation of aromatic aldehydes (1) must be studied in strongly alkaline media. Acidity functions for strongly alkaline aqueous solutions of alkali metal and quaternary ammonium hydroxides, corresponding to dissociation of proton (H ), are well established (2, 3). Substituted anilines and diphenylamines (4,5) and indoles (6) were used as acid-base indicators for establishment of such scales, but whether an acidity scale based on one type of indicator can be rigorously applied to acid-base equilibria involving structurally different acidic groups for reactions in strongly alkaline media remains questionable. For substituted anilines, behavior both parallel (7) and nonparallel (8) to the H scale based on indole derivatives has been reported. The limited solubility of anilines in aqueous solutions of alkali metal hydroxides, the reactions of the aniline derivative with more than one hydroxide ion, irreversible substitution reactions (9), and the possibility of hydroxide ion addition rather than... 

The quality and yield of carbon black depends on the quality of the feedstock, reactor design, and input variables. The structure is controlled by the addition of alkali metals to the reaction or mixing zones. Usual practice is to use aqueous solutions of alkali metal salts such as potassium chloride or potassium hydroxide sprayed into the combustion chamber or added to the make oil in the oil injector. Alkaline-earth compounds such as calcium acetate that increase the specific surface area are introduced in a similar manner. 

As the carbon black structure may be reduced by the presence of alkali metal ions in the reaction zone [4.11], alkali metal salts, preferably aqueous solutions of potassium hydroxide or potassium chloride, are often added to the make oil in the oil injector. Alternatively, the additives may be sprayed separately into the combustion chamber. In special cases, other additives, e.g., alkaline-earth metal compounds which increase the specific surface area are introduced in a similar manner. 

The phase transfer catalyzed alkylation reaction of dodecyl phenyl glycidyl ether (DPGE) with hydroxyethyl cellulose (HEC) was studied as a mechanistic model for the general PTC reaction with cellulose ethers. In this way, the most effective phase transfer catalysts and optimum reaction concentrations could be identified. As a model cellulose ether, CELLOSIZE HEC11 was chosen, and the phase transfer catalysts chosen for evaluation were aqueous solutions of choline hydroxide, tetramethyl-, tetrabutyl-, tetrahexyl-, and benzyltrimethylammonium hydroxides. The molar A/HEC ratio (molar ratio of alkali to HEC) used was 0.50, the diluent to HEC (D/HEC) weight ratio was 7.4, and the reaction diluent was aqueous /-butyl alcohol. Because some of the quaternary ammonium hydroxide charges would be accompanied by large additions of water, the initial water content of the diluent was adjusted so that the final diluent composition would be about 14.4% water in /-butyl alcohol. The results of these experiments are summarized in Table 2. 

Sulfasalazine. Salicylazosulfapyridine or Azulfadine [599-79-1] (2-hydroxy-5-[[4[(2-pyridylamino)sulfonyl]-phenyl]azo] benzoic acid) (15) is a light brownish yellow-to-bright yellow fine powder that is practically tasteless and odorless. It melts at ca 255°C with decomposition, is very slightly soluble in ethanol, is practically insoluble in water, diethyl ether, chloroform, and benzene, and is soluble in aqueous solutions of alkali hydroxides. Sulfasalazine may be made by the synthesis described in Reference 13. It is not used as an antidiarrheal as such, but is indicated for the treatment of inflammatory bowel diseases such as ulcerative colitis and Crohn s disease. Its action is purported to result from the breakdown in the colon to 5-aminosalicylic acid [89-57-6] (5-AS A) and sulfapyridine [144-83-2]. It may cause infertility in males, as well as producing idiosyncratic reactions in some patients these reactions have been attributed to the sulfa component of the compound. The mechanism of 5-ASA is attributed to inhibition of the arachidonic acid cascade preventing leukotriene B4 production and the ability to scavenge oxygen free radicals. The active component appears to be 5-aminosalicylic acid. 

Alkali hydroxides and ammonium hydroxide convert the dihalides to oxides, R2TeO, aqueous solutions of these products having an alkaline reaction. This may be due to the formation of a hydroxide, R2Te(OH)2, but such products do not appear to be stable in the solid state. 

This difference in kinetics was exploited to develop a procedure to determine free and reversibly bound sulfite in food. The mobile phase consisted of an aqueous solution of 0.05 M tetra-butylammonium hydroxide adjusted to the desired pH by the addition of glacial acetic acid (34). Fluorimetric detection is also possible, because a reaction of the formaldehyde-bisulfite complex with 5-aminofluorescein gives a nonfluorescent product. The sulfite is measured indirectly by its suppresion of the fluorescence of the reagent (31). This method is applicable to the determination of S02 at > 10 ppm and is not applicable to dark-colored foods or ingredients where SO, is strongly bound, e.g., caramel color. This method does not detect naturally occurring sulfite. Sulfur dioxide is released by direct alkali extraction. 

M. D. Alexander, "Reactions of the Alkali Metals with Water A Novel Demonstration/ J. Chem. Educ., Vol. 69,1992,418. The reaction of sodium metal with water to produce an aqueous solution of sodium hydroxide and hydrogen gas is performed at the interface between paint thinner and the more dense water. Periodically, bubbles of hydrogen gas carry the sodium metal into the organic layer, temporarily stopping the reaction. The presence of the aqueous layer is shown by a phenol-phthalein indicator color change. 

Reactions of Electrons and Holes in Frozen Aqueous Solutions of Alkali Hydroxides... 

The Electron Excess Center. In their earlier paper Schulte-Frohlinde and Eiben (57) had assigned the line A to the O ion and the other line to the stabilized electron subsequently they have reversed this assignment, and are therefore in agreement with other authors. However, the line with g = 2.0006 has been interpreted in different ways, although all interpretations relate it to the radiation-produced electron. Thus Schulte-Frohlinde and Eiben (57, 58) consider the species responsible for this line to be a stabilized free electron, while Ershov et al. (16) and Henriksen (23) identify it with a solvated electron or a po-laron in the same sense as these two terms are used in the radiation chemistry of water and aqueous solutions. According to the above authors, this species is not found in pure ice because of Reaction 30, whereas in alkaline systems such a reaction should not occur. (Henriksen does not offer any explanation about the specific role of alkali hydroxide in stabilizing the solvated electron. ) Both of these hypotheses can be shown to be incorrect. Thus, if Reaction 30 occurred to any extent in pure ice, one should be able to detect H atoms in neutral ice with a yield of at least as high as the maximum yield of the solvated electrons, viz.. 

The reaction of adducts with alkali hydroxides have been studied for cyanoisochromenes 108, which are oxygen analogs of Reissert compounds described for the first time by Balaban and co-workers (87T409). In this case, sodium hydroxide, depending on its concentration in aqueous solutions and on the nature of R3 in 108, may act both as a base and as a... 

The formation of /3-naphthols 209 occurs readily on treatment of salts of type 154 with dilute alkaline aqueous solutions, but this reaction competes with other processes when concentrated alkali hydroxide solutions are used (cf. Section III,F,2,c). 

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