Acid, strong

By hydrolysis of substituted malonic esters with 50 per cent, potassium hydroxide, followed by decarboxylation of the resulting malonic add by heating above the m.p. or, better, by rendering the aqueous solution of the potassium salt of the dibasic acid strongly acid and refluxing the mixture, for example ... 

Ion-exchange resins are categorized by the nature of functional groups attached to a polymeric matrix, by the chemistry of the particular polymer in the matrix, and by the porosity of the polymeric matrix. There are four primary types of functionaHty strong acid, weak acid, strong base, and weak base. Another type consists of less common stmctures in specialty resins such as those which have chelating characteristics. 

Corrosion Resistance. Zirconium is resistant to corrosion by water and steam, mineral acids, strong alkaUes, organic acids, salt solutions, and molten salts (28) (see also Corrosion and corrosion control). This property is attributed to the presence of a dense adherent oxide film which forms at ambient temperatures. Any break in the film reforms instantly and spontaneously in most environments. 

BgHg] , and [B H ] closo anions are stable ia neutral and alkaline solutions but react rapidly with aqueous acid. Strongly acidic solutions... 

Inorganic Acids. Strong inorganic acids have little antimicrobial activity in themselves but inhibit microorganism growth by lowering the pH. Disinfectant toilet bowl cleaners that contain 9.5% HCl or more are antimicrobial. Carbonic acid [463-79-6] in soft drinks provides some antibacterial preservation. Sulfurous acid [7782-99-2] is an effective preservative used to preserve wines (see Wine), fmit juices (qv), and dried fmits. 

The principal applications of these plastics arose from their very good chemical resistance, as they are resistant to mineral acids, strong alkalis and most common solvents. They were, however, not recommended for use in conjunction with oxidising acids such as fuming nitric acid, fuming sulphuric acid or chlorosulphonic acid, with fluorine or with some chlorinated solvents, particularly at elevated temperatures. 

Decomposition of trichloroethylene can occur upon contact with naked flames, red-hot surfaces, hot elements of electric heaters, or intense UV light with the generation of acidic and highly-toxic products. The presence of reactive contaminants, e.g. acids, strong alkalis, highly-reactive metals, may also result in decomposition to similar products. 

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 ... 

Results of the sulfur tetrafluoride fluorination of benzenecarboxylic acids strongly depend on the nature of a benzene ring substituent Benzoic, toluic, and particularly p-methoxybenzoic acids give poor yields of the respective benzotri-... 

Scheeren et al. reported the first enantioselective metal-catalyzed 1,3-dipolar cycloaddition reaction of nitrones with alkenes in 1994 [26]. Their approach involved C,N-diphenylnitrone la and ketene acetals 2, in the presence of the amino acid-derived oxazaborolidinones 3 as the catalyst (Scheme 6.8). This type of boron catalyst has been used successfully for asymmetric Diels-Alder reactions [27, 28]. In this reaction the nitrone is activated, according to the inverse electron-demand, for a 1,3-dipolar cycloaddition with the electron-rich alkene. The reaction is thus controlled by the LUMO inone-HOMOaikene interaction. They found that coordination of the nitrone to the boron Lewis acid strongly accelerated the 1,3-dipolar cycloaddition reaction with ketene acetals. The reactions of la with 2a,b, catalyzed by 20 mol% of oxazaborolidinones such as 3a,b were carried out at -78 °C. In some reactions fair enantioselectivities were induced by the catalysts, thus, 4a was obtained with an optical purity of 74% ee, however, in a low yield. The reaction involving 2b gave the C-3, C-4-cis isomer 4b as the only diastereomer of the product with 62% ee. 

Of the several syntheses available for the phenothiazine ring system, perhaps the simplest is the sulfuration reaction. This consists of treating the corresponding diphenylamine with a mixture of sulfur and iodine to afford directly the desired heterocycle. Since the proton on the nitrogen of the resultant molecule is but weakly acidic, strong bases are required to form the corresponding anion in order to carry out subsequent alkylation reactions. In practice such diverse bases as ethylmagnesium bromide, sodium amide, and sodium hydride have all been used. Alkylation with (chloroethyl)diethylamine affords diethazine (1), a compound that exhibits both antihista-minic and antiParkinsonian activity. Substitution of w-(2-chloroethyl)pyrrolidine in this sequence leads to pyrathiazine (2), an antihistamine of moderate potency. 

As will have become apparent, nickel and corrosion-resistant nickel alloys have wide ranges of application, particularly in industries where strongly acidic, strongly alkaline or strongly saline environments are encountered. Table 4.29 lists some of the more important applications in those industries where these conditions most frequently arise, i.e. in the chemical, petrochemical, oil and gas, nuclear and conventional power generating, textile, paper, marine, desalination and food processing industries. The list is by no means exhaustive and there are many other applications of a similar nature in these and other industries. The table should, nevertheless, serve... 

Other polyethers The chlorine-containing polyether Penton has excellent resistance to mineral acids, strong alkalis and most common solvents. It is not recommended for use with oxidising acids such as fuming nitric acid. 

There are two types of acids, strong and weak, which differ in the extent of their ionization in water. Strong acids ionize completely, forming H+ ions and anions. A typical strong acid is HC1. It undergoes the following reaction on addition to water ... 

There is considerable evidence to indicate that the neutralization reaction occurs when any strong base reacts with any strong acid in water solution. It follows that the neutralization equation written above applies to any strong acid-strong base reaction. 

Weak acid-strong base. When a strong base such as NaOH is added to a solution of a weak acid, HB, a two-step reaction occurs. The first step is the ionization of the HB molecule to H+ and B ions the second is the neutralization of the H+ ions produced in the first step by the OH- ions of the NaOH solution. 

Identify the type of aqueous reaction using the symbols PPT for pre-dpitation, SA/SB for strong acid-strong base, SA/WB for strong acid-weak base, WA/SB for weak acid-strong base, and NR for no reaction. 

In a strong acid-strong base titration, pH changes very rapidly near the end point. 

A weak acid-strong base titration. The curve represents the titration of 50.00 mL of 1.000 M acetic acid, HC2H3O2. with 1.000 /W NaOH. The solution at the equivalence point is basic (pH = 9.22). Phenolphthalein is a suitable indicator. Methyl red would change color much too early, when only about 33 mL of NaOH had been added. Bromthymol blue would change color slightly too quickly. 

From Figure 14.5 and Example 14.7, we conclude that any indicator that changes ccdor between pH 4 and 10 should be satisfactory for a strong acid-strong base titration. Bromthymol blue (BB end point pH = 7) would work very well, but so would methyl red (MR end point pH = 5) or phenolphthalein (PP end point pH = 9). 

A typical weak acid-strong base titration is that of acetic acid with sodium hydroxide. The net ionic equation for the reaction is... 

From Figure 14.6 and Example 14.8, it should be clear that the indicator used in this titration must change color at about pH 9. Phenolphthalein (end point pH = 9) is satisfactory. Methyl red (end point pH = 5) is not suitable. If we used methyl red, we would stop the titration much too early, when reaction is only about 65% complete. This situation is typical of weak acid-strong base titrations. For such a titration, we choose an indicator that changes color above pH 7. 

Strategy Once you realize that this is a weak acid-strong base titration, the problem unravels follow the rules cited in Table 14.3. 

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