Potassium hydroxide Strong bases

In place of potassium hydroxide, strong organic bases or suitable ion exchangers, such as, for example, Dowex-2, can also be used. 

The N-2 atom in l,2-dihydro-l-methyl-2,3,l-benzodiazaborine can easily be methylated by DMS in the presence of potassium hydroxide. This base is not sufficiently strong to be used in (V-alkylation of the nitrogen in benzo fused l,2-dihydro-l,2-azaborines in this case organolithium compounds can be employed. By successive treatment of (177 R = H) with methyllithium and an alkyl halide a number of A-alkyl derivatives have been prepared. 

Maleic Anhydride. The ACGIH threshold limit value in air for maleic anhydride is 0.25 ppm and the OSHA permissible exposure level (PEL) is also 0.25 ppm (181). Maleic anhydride is a corrosive irritant to eyes, skin, and mucous membranes. Pulmonary edema (collection of fluid in the lungs) can result from airborne exposure. Skin contact should be avoided by the use of mbber gloves. Dust respirators should be used when maleic anhydride dust is present. Maleic anhydride is combustible when exposed to heat or flame and can react vigorously on contact with oxidizers. The material reacts exothermically with water or steam. Violent decompositions of maleic anhydride can be catalyzed at high temperature by strong bases (sodium hydroxide, potassium hydroxide, calcium hydroxide, alkaU metals, and amines). Precaution should be taken during the manufacture and use of maleic anhydride to minimize the presence of basic materials. 

Anionic Polymerization of Cyclic Siloxanes. The anionic polymerization of cyclosiloxanes can be performed in the presence of a wide variety of strong bases such as hydroxides, alcoholates, or silanolates of alkaH metals (59,68). Commercially, the most important catalyst is potassium silanolate. The activity of the alkaH metal hydroxides increases in the foUowing sequence LiOH < NaOH < KOH < CsOH, which is also the order in which the degree of ionization of thein hydroxides increases (90). Another important class of catalysts is tetraalkyl ammonium, phosphonium hydroxides, and silanolates (91—93). These catalysts undergo thermal degradation when the polymer is heated above the temperature requited (typically >150°C) to decompose the catalyst, giving volatile products and the neutral, thermally stable polymer. 

Vinyl chloride reacts with sulfides, thiols, alcohols, and oximes in basic media. Reaction with hydrated sodium sulfide [1313-82-2] in a mixture of dimethyl sulfoxide [67-68-5] (DMSO) and potassium hydroxide [1310-58-3], KOH, yields divinyl sulfide [627-51-0] and sulfur-containing heterocycles (27). Various vinyl sulfides can be obtained by reacting vinyl chloride with thiols in the presence of base (28). Vinyl ethers are produced in similar fashion, from the reaction of vinyl chloride with alcohols in the presence of a strong base (29,30). A variety of pyrroles and indoles have also been prepared by reacting vinyl chloride with different ketoximes or oximes in a mixture of DMSO and KOH (31). 

Strong bases such as methan olic potassium hydroxide, sodium methoxide, or 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU), cause epimerization at the C-2 carbon or shift the beta-gamma double bond into conjugation with the lactone carbonyl (Fig. 4) (25,26). 

In addition to the formulation parameters mentioned above, selection of the base used for catalysis has strong implications. Bases commonly used are sodium hydroxide, potassium hydroxide, lithium oxide, calcium hydroxide, barium hy-... 

A base is any material that produces hydroxide ions when it is dissolved in water. The words alkaline, basic, and caustic are often used synonymously. Common bases include sodium hydroxide (lye), potassium hydroxide (potash lye), and calcium hydroxide (slaked lime). The concepts of strong versus weak bases, and concentrated versus dilute bases are exactly analogous to those for acids. Strong bases such as sodium hydroxide dissociate completely while weak bases such as the amines dissociate only partially. As with acids, bases can be either inorganic or organic. Typical reactions of bases include neutralization of acids, reaction with metals, and reaction with salts ... 

JA5190, 940M5132). Proton abstraction from 109 gives a neutral ti C) 2-thienyl complex, 110. Such a reaction becomes impossible in case of the 2,5-dimethylthiophene analog of 109. However, use of a strong base such as potassium hydroxide in methanol gives 111. An attempted transformation of 109 to 110 by protonation with triflic acid leads, however, to the thienylcarbene complex cation 112 where the aromaticity is disrupted. 

The almost dry residue is cooled to 0°C and made strongly alkaline with a 50% potassium hydroxide solution. The amine is extracted into several portions of ether, dried over potassium hydroxide, the solvent removed, and the base fractioned. Reaction of the base with a half-molar quantity of sulfuric acid gives the sulfate. 

The two most common elimination reactions arc dehydroUalogenalion—the loss of HX from an alkyl halide—and dehydration—(he loss of water from an alcohol. Dehydrohalogenation usually occurs by reaction of an alkyl halide with strong base such as potassium hydroxide. For example, bromocvclohexane yields cyclohexene when treated with KOH in ethanol solution. 

Earlier investigators employed strong bases (sodium hydroxide, potassium hydroxide) or platinum on asbestos to... 

Aqueous solutions of many salts, of the common strong acids (hydrochloric, nitric and sulphuric), and of bases such as sodium hydroxide and potassium hydroxide are good conductors of electricity, whereas pure water shows only a very poor conducting capability. The above solutes are therefore termed electrolytes. On the other hand, certain solutes, for example ethane-1,2-diol (ethylene glycol) which is used as antifreeze , produce solutions which show a conducting capability only little different from that of water such solutes are referred to as non-electrolytes. Most reactions of analytical importance occurring in aqueous solution involve electrolytes, and it is necessary to consider the nature of such solutions. 

In IC this problem of electrolyte background is overcome by means of eluant suppression. Thus in the above example of sodium and potassium analysis, if the effluent from the separating column is passed through a strong base anion exchange resin in the hydroxide form (suppressor column) the following two processes occur ... 

Discussion. The hydroxides of sodium, potassium, and barium are generally employed for the preparation of solutions of standard alkalis they are water-soluble strong bases. Solutions made from aqueous ammonia are undesirable, because they tend to lose ammonia, especially if the concentration exceeds 0.5M moreover, it is a weak base, and difficulties arise in titrations with weak acids (compare Section 10.15). Sodium hydroxide is most commonly used because of its cheapness. None of these solid hydroxides can be obtained pure, so that a standard solution cannot be prepared by dissolving a known weight in a definite volume of water. Both sodium hydroxide and potassium hydroxide are extremely hygroscopic a certain amount of alkali carbonate and water are always present. Exact results cannot be obtained in the presence of carbonate with some indicators, and it is therefore necessary to discuss methods for the preparation of carbonate-free alkali solutions. For many purposes sodium hydroxide (which contains 1-2 per cent of sodium carbonate) is sufficiently pure. 

However, many salts such as the hydroquinone or biphenol salt are so insoluble diat they do not work well by this procedure. Furthermore, a stoichiometric amount of base used for die reaction is critical to obtain high-molecular-weight polymers. Moreover, die sd ong base may undesirably hydrolyze the dihalides to afford deactivated diphenolates, which upset the stoichiometry. Clendining et al. reported that potassium carbonate or bicarbonate could be used in these reactions instead of corresponding hydroxides.60 McGrath and co-workers were the first to systematically study die use of the weak base K2C03 instead of a strong base to obtain phenolate salts.8,61,62 Potassium carbonate was found to be better than... 

An aqueous solution of potassium hydroxide contains K , OH, and H2 O. Phosphoric acid is a weak acid, so most of its molecules remain as H3 PO4 in aqueous solution. The species present at the beginning of the reaction are K and OH ions and molecules of H3 PO4 and H2 O. The hydroxide ion is a powerful base that removes all of the acidic hydrogen atoms from both strong and weak acids. 

Likewise, when a strong base such as potassium hydroxide dissolves in water, it dissociates into its ions, too ... 

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