SOLUTIONS CAN BE ACIDIC, BASIC, OR NEUTRAL

Was this your answer Yes, but not to any large extent. When they do react, they form hydronium and hydroxide ions. Note Make sure you understand this point because it serves as a basis for most of the rest of the chapter.) 

Further experiments reveal an interesting rule pertaining to the concentrations of hydronium and hydroxide ions in any solution that contains water. The concentration of hydronium ions in any aqueous solution multiplied by the 

Concentration k usually given as molarity, which is indicated by abbreviating this equation using brackets  

The brackets mean this eejuation is read the molarity of H3O times the molarity of OH equals K , Writing in scientific notation (sec Appendix A), we have 

For pure water, the value of K , is the concentration of hydronium ions, 

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Two questions become apparent. First, how can you predict whether a particular salt solution will be acidic, basic, or neutral Then, how can you calculate the concentrations of ion and OH ion in the salt solution (or equivalently, how... 

The self-ionization of water may seem inconsequential at first, since the percent of ionization is very low and the resulting product neutral however, it has a major impact on the equilibrium achieved in the aqueous solutions of salts. Because salts dissociate into their constituent ions when dissolved, these ions can, and often do, interact with the ions produced by water s self-ionization. The result is a solution that can be acidic, basic, or neutral depending on how the equilibrium shifts to accommodate the ions. 

As mentioned earlier, it is desirable to initiate the isolation process on the basis of simple extraction or partition methods as exemplified by the first four methods listed above (see Chapter 8). Frequently, it is possible to extract impurities selectively on the basis of acidity, basicity, or neutrality of the compounds in question.2 The extraction process usually involves liquid-liquid extraction, where one phase is an aqueous solution and the other is a nonpolar organic phase. By appropriate adjustment of the pH of the aqueous solution, one can extract acidic, basic, or neutral impurities. These methods work well when a few impurities are present and their polarity or pKa is sufficiently different from that of API. If necessary, further separations can be achieved by chromatographic methods. 

At the end of Chapter 8, you learned that when just enough acid and base have been mixed for a complete reaction, the solution can be acidic, neutral, or basic. The reaction between an acid and a base forms an aqueous solution of a salt. The properties of the dissolved salt determine the pH of a titration solution at equivalence. Figure 9.1 shows the acidic, basic, or neutral properties of three salt solutions. 

An aqueous solution can be described as acidic, basic, or neutral, as Figure 10.11 summarizes. An acidic solution is one in which the hydronium ion... 

PET hydrolysis takes place by reaction with liquid water or steam, leading to the formation of terephthalic acid. The process can be carried out under acid, basic or neutral conditions. Although stronger conditions are necessary to promote PET depolymerization by neutral hydrolysis, this a preferred alternative because large amounts of aqueous salt solutions are produced in the acid and alkali catalysed degradations. 

Salt solutions can be acidic, neutral, or basic. Let s consider a salt solution of NaF. NaF dissolves in water to form sodium and fluoride ions. 

The increased presence of hydroxide ions (notice the formation of hydroxide ions as one of products of the hydrolysis reaction) makes the solution basic. This strategy can be used to predict whether a salt solution is acidic, basic, or neutral. 

The 20 common amino acids can be further classified as neutral, acidic, or basic, depending on the structure of their side chains. Fifteen of the twenty have neutral side chains, two (aspartic acid and glutamic acid) have an extra carboxylic acid function in their side chains, and three (lysine, arginine, and histidine) have basic amino groups in their side chains. Note that both cysteine (a thiol) and tyrosine (a phenol), although usually classified as neutral amino acids, nevertheless have weakly acidic side chains that can be deprotonated in strongly basic solution. 

Substitution of the free epoxide, which generally occurs under basic or neutral conditions, usually involves an Sn2 mechanism. Since primary substrates undergo Sn2 attack more readily than secondary, unsymmetrical epoxides are attacked in neutral or basic solution at the less highly substituted carbon, and stereospecifically, with inversion at that carbon. Under acidic conditions, it is the protonated epoxide that undergoes the reaction. Under these conditions the mechanism can be either SnI or Sn2. In S l mechanisms, which favor tertiary carbons, we might expect that attack would be at the more highly substituted carbon, and this is indeed the case. However, even when protonated epoxides react by the 8 2 mechanism, attack is... 

Oxide hydrosols synthesis relies on the destabilization of a true solution by a pH change. In order to prepare palladium oxide colloidal particles, two experimental routes can be carried out the neutralization of an acidic (basic) solution by an alkaline (acidic) solution, or thermohydrolysis of the palladium precursor solution. 

Whereas all the alkylations in Figure 2.31 take place in basic or neutral solutions, carboxylic acids can be directly methylated with diazomethane (Figure 2.32). The actual nucleophile (the carboxylate ion) and the actual methylating agent (H3C—N N) are produced from the reaction partners by proton transfer. 

In a titration, you are presented with an acid or base of an unknown molarity. You then use an acid or base of a known molarity to neutralize the unknown. The process is done slowly with the use of burets to deliver exact amounts of acid and base. Finally, you use an indicator to help determine the end point of the reaction. When the indicator changes color, the end point has been reached and the acid and base have neutralized each other. Titrations need to be so carefully controlled that often just one drop of acid or base added to the reaction flask can mean the difference between the solution s being acidic or basic. This can be seen by the steep slope of the line in the graph in Figure 9.4. 

The various steps that characterize the transport of metal species through SLMs can be described with the help of Figure 31.4. Step 1 The metal species, after diffusing to the source-membrane interface, react with the metal carrier, ions are simultaneously released into the feed solution (counter-transport, acidic carrier) or ions accompany the metal ions into the membrane (cotransport, neutral, or basic carriers). Step 2 The metal-carrier complex diffuses across the membrane because its concentration gradient is negative. Step 3 At the membrane-receiver interface the metal-carrier complex releases metal ions into the aqueous phase, ions replace M ions into the membrane (counter-transport) or X ions are simultaneously released together with M ions into the strip solution (cotransport). Step 4 The uncomplexed carrier diffuses back across the membrane. 

The epoxidation of unsaturated materials is the most commonly used reaction of dioxiranes. The reaction, whether carried out in situ or using the solution method, gives high yields of epoxides, usually in rapid reactions. The isolated dioxirane method is particularly useful in cases where oxidation products are sensitive to the acidic conditions of the most commonly used epoxidation reagents or the basic conditions of the in situ method. Use of the isolated dioxirane permits reaction under neutral conditions so that labile epoxides are conveniently prepared. When the desired epoxide is sensitive to moisture, the dioxirane solution can be dried with molecular sieves for use in such epoxidations. The epoxidation of water-insoluble alkenes with the in situ method requires the use of a phase-transfer catalyst, but the reaction still proceeds in high yields. Dioxiranes, in situ generated... 

Hydrolysis of conjugate base (A ) of weak acid > basic solution and Hydrolysis of conjugate acid (BH ) of weak base > acidic solution. This solution can be basic, neutral, or acidic, depending on which hydrolysis occurs to a greater extent use K, and K, values for the hydrolysis reactions to tell which ion wiU be the dominant fector. (We did not do calculations for this type of salt.)... 

If a dilution step is required, dilution into a pH 7.4 buffer is better than directly into water, because buffer can help ionize basic or acidic compounds and improve solubility. Water has no buffer capacity, and a compound added from DMSO will be in its neutral state and have only limited intrinsic solubility. Salt forms tend to be soluble in water. Dissolving in buffer will ensure no conversion back to the free acid or base and the solution will have a consistent pH. 

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