Bases basic solutions

Weak acid + Strong base ---- Basic solution... 

Like acids, bases are corrosive. Bases can cause burns and damage tissue. You should never touch or taste a substance to find out whether it is a base. Basic solutions contain ions and can conduct electricity. Basic solutions are not as reactive with metals as acidic solutions are. 

For chemical processes, some examples are the elimination of aromatics by sulfonation, the elimination of olefins by bromine addition on the double bond (bromine number), the elimination of conjugated diolefins as in the case of the maleic anhydride value (MAV), and the extraction of bases or acids by contact with aqueous acidic or basic solutions. 

The concentration of nitromethane, CH3NO2, can be determined from the kinetics of its decomposition in basic solution. In the presence of excess base the reaction is pseudo-first-order in nitromethane. For a standard solution of 0.0100 M nitromethane, the concentration of nitromethane after 2.00 s was found to be 4.24 X 10 M. When a sample containing an unknown amount of nitromethane was analyzed, the concentration remaining after 2.00 s was found to be 5.35 X 10 M. What is the initial concentration of nitromethane in the sample ... 

The AsF ion is very stable toward hydrolysis in aqueous solution. It is not hydroly2ed by boiling a strongly basic solution almost to dryness (26), although it is hydroly2ed in sulfuric acid (27) or in boiling perchloric acid (26). The hydrolysis of AsF in concentrated sulfuric acid (27) and in base (28) at 193—222°C is first order in AsF . The hydrolysis of AsF in alkaline solution is slower than either PF or SbF . ... 

Bromates are stable in storage. They have various uses based on their oxidizing power. Bromates can be formed by the disproportionation of bromine in basic solution ... 

Adolph Baeyer is credited with the first recognition of the general nature of the reaction between phenols and aldehydes in 1872 ([2,5-7] [18], Table 5.1). He reported formation of colorless resins when acidic solutions of pyrogallic acid or resorcinol were mixed with oil of bitter almonds, which consists primarily benzaldehyde. Baeyer also saw resin formation with acidic and basic solutions of phenol and acetaldehyde or chloral. Michael and Comey furthered Baeyer s work with additional studies on the behavior of benzaldehyde and phenols [2,19]. They studied a variety of acidic and basic catalysts and noted that reaction vigor followed the acid or base strength of the catalyst. Michael et al. also reported rapid oxidation and darkening of phenolic resins when catalyzed by alkaline materials. 

In the sulfuric acid solvent system, compounds that enhance the concentration of the solvo-cation HSO4- will behave as bases and those that give rise to H3S04 will behave as acids (p. 425). Basic solutions can be formed in several ways of which the following examples are typical ... 

Ester hydrolysis in basic solution is called saponification, after the Latin word sapo, meaning "soap." As we ll see in Section 27.2, soap is in fact made by boiling animal fat with base to hydrolyze the ester linkages. 

You are probably familiar with a variety of aqueous solutions that are either acidic or basic (Figure 4.6). Acidic solutions have a sour taste and affect the color of certain organic dyes known as acid-base indicators. For example, litmus turns from blue to red in acidic solution. Basic solutions have a slippery feeling and change the colors of indicators (e.g., red to blue for litmus). 

The flask contains vinegar (a dilute solution of acetic acid) and an add-base indicator (phenolphthalein) that is colorless in add solution and pink in basic solution. 

Bromopyrogallol red. This metal ion indicator is dibromopyrogallol sulphon-phthalein and is resistant to oxidation it also possesses acid-base indicator properties. The indicator is coloured orange-yellow in strongly acidic solution, claret red in nearly neutral solution, and violet to blue in basic solution. The dyestuff forms coloured complexes with many cations. It is valuable for the determination, for example, of bismuth (pH = 2-3. nitric acid solution endpoint blue to claret red). 

A kinetic study of the deuteration of pyridones and quinolones by deuterated sulphuric acid yielded the data in Table 148sl0. For the 4-pyridones, the rapid rise in rate with increasing acidity in strongly basic solutions, and the levelling off in rate at about H0 = 0 is consistent with reaction on the free base as is the small negative entropy of activation. The similarity in rate between 4-pyridone and its 1-methyl derivative shows reaction to take place on the form (XII) and not (XIII), viz. 

All anions that are the conjugate bases of weak acids produce basic solutions. For example, formic acid, HCOOH, the acid in ant venom, is a weak acid, and so the formate ion acts as a base in water ... 

One common indicator is phenolphthalein (Fig. 11.10). The acid form ol this large molecule (3) is colorless its conjugate base form (4) is pink. The structure of the base form of phenolphthalein allows electrons to be delocalized across all three of the benzenelike rings of carbon atoms, and the increase in delocalization is part of the reason for the change in color. The pFCIn of phenolphthalein is 9.4, and so the end point occurs in slightly basic solution. Litmus, another well-known indicator, has pkln = 6.5 it is red for pH < 5 and blue for pH > 8. 

The oxidation is slow in acidic solution but rapid in basic solution, where insoluble iron(III) hydroxide, Fe(OH)3, is precipitated. Although [Fe(H20)6]3+ ions are pale purple and Fe3 1 ions give amethyst its purple color, the colors of aqueous solutions of iron(III) salts are dominated by the conjugate base of [Fe(H20)g]3+, the yellow [Fe0H(H20)d2+ ion ... 

Although most acidity functions have been applied only to acidic solutions, some work has also been done with strongly basic solutions. The H function, which is used for highly acidic solutions when the base has a charge of — 1, can also be used for strongly basic solvents, in which case it measures the ability of these solvents to abstract a proton from a neutral acid BH. When a solvent becomes protonated, its conjugate acid is known as a lyonium ion. 

For those substrates more susceptible to nucleophilic attack (e.g., polyhalo alkenes and alkenes of the type C=C—Z), it is better to carry out the reaction in basic solution, where the attacking species is RO . The reactions with C=C—Z are of the Michael type, and OR goes to the side away from the Z. Since triple bonds are more susceptible to nucleophilic attack than double bonds, it might be expected that bases would catalyze addition to triple bonds particularly well. This is the case, and enol ethers and acetals can be produced by this reaction. Because enol ethers are more susceptible than triple bonds to electrophilic attack, the addition of alcohols to enol ethers can also be catalyzed by acids. " One utilization of this reaction involves the compound dihydropyran... 

The second oxidation, which is normally slower than the first (which is why sulfoxides are so easily isolable), has the same mechanism in neutral or acid solution, but in basic solution it has been shown that the conjugate base of the peroxy compound (R 00 ) also attacks the SO group as a nucleophile " ... 

The strong base is a soluble hydroxide that ionizes completely in water, so the concentration of OH matches the 0.25 M concentration of the base. For the weak base, in contrast, the equilibrium concentration of OH is substantially smaller than the 0.25 M concentration of the base. At any instant, only 0.8% of the ammonia molecules have accepted protons from water molecules, producing a much less basic solution in which OH is a minor species. The equilibrium concentration of unproton-ated ammonia is nearly equal to the Initial concentration. Figure 17-7 summarizes these differences. 

Aluminas. Aluminas, porous AI2O3, are available in many forms. They constitute the most important carrier material in heterogeneous catalysis. Alumina is amphoteric and, as a con.sequence, soluble in both acidic and basic media. Precipitation can be performed from an acid solution by adding a base or from a basic solution by adding an acid, as schematically represented in Fig. 3.18. If, for example, at a pH of less than about 3 a base is added to an aqueous solution of aluminium sulphate, a precipitate is formed. If this material is filtered, dried and calcined, an amorphous porous AI2O3 is obtained. At other pH values different porous aluminas can be synthesized. 

We shall consider the voltammetric behavior of a base at the 0/W interface. In the discussion stated above it is assumed that the transfer process of drugs at the 0/W interface is of reversible nature (see the assumptions 1-6 above). With increasing pH of the W phase, particularly in basic solutions, however, the rate of protonation in the W phase, that is, B(W) - - H+(W) = BH+(W) should rapidly decrease, resulting in decreasing of the current associated with the transfer of BH+ ion across the O/W interface. This has actually... 

In an acid-base neutralization reaction, the hydronium (hydrogen) ions of the acidic solution react with the hydroxide ions in the basic solution. The reaction may be shown by this equation. 

Indicators are chemical dyes that change color with a change of pH. Litmus paper and phenolphthalein are two common indicators used in acid-base reactions. They are chosen because they change color at or very near solution neutrality. Litmus paper is red in acidic solutions and blue in basic solutions. Phenolphthalein is colorless in acidic solutions and turns red in basic solutions. 

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