Example Solutions

A traditional method for such reductions involves the use of a reducing metal such as zinc or tin in acidic solution. Examples are the procedures for preparing l,2,3,4-tetrahydrocarbazole[l] or ethyl 2,3-dihydroindole-2-carbox-ylate[2] (Entry 3, Table 15.1), Reduction can also be carried out with acid-stable hydride donors such as acetoxyborane[4] or NaBHjCN in TFA[5] or HOAc[6]. Borane is an effective reductant of the indole ring when it can complex with a dialkylamino substituent in such a way that it can be delivered intramolecularly[7]. Both NaBH -HOAc and NaBHjCN-HOAc can lead to N-ethylation as well as reduction[8]. This reaction can be prevented by the use of NaBHjCN with temperature control. At 20"C only reduction occurs, but if the temperature is raised to 50°C N-ethylation occurs[9]. Silanes cun also be used as hydride donors under acidic conditions[10]. Even indoles with EW substituents, such as ethyl indole-2-carboxylate, can be reduced[ll,l2]. 

In a simple liquid-liquid extraction the solute is partitioned between two immiscible phases. In most cases one of the phases is aqueous, and the other phase is an organic solvent such as diethyl ether or chloroform. Because the phases are immiscible, they form two layers, with the denser phase on the bottom. The solute is initially present in one phase, but after extraction it is present in both phases. The efficiency of a liquid-liquid extraction is determined by the equilibrium constant for the solute s partitioning between the two phases. Extraction efficiency is also influenced by any secondary reactions involving the solute. Examples of secondary reactions include acid-base and complexation equilibria. 

Hydrolysis of metal-organic solutions Example. Ba(OC3H7)2 + Ti(OC5Hu)4 + H2O — BaTiOs (Barium isopropoxide and Titanium tertiary amyloxide are refluxed in isopropanol and then hydrolyzed with de-ionized water to produce a sol-gel. ... 

The Number of Dipoles per Unit Volume. The Entropy Change Accompanying Proton Transfers. The Equilibrium between a Solid and Its Saturated Solution. Examples of Values of L and AF°. The Change of Solubility with Temperature. Uni-divalent and Other Solutes. Lithium Carbonate in Aqueous Solution. H2COj in Aqueous Solution. Comparison between HjCOj and Li2C03 in Aqueous Solution. Heats of Solution and the Conventional Free Energies and Entropies of Solution. 

The fact that strong acids and bases are completely ionized in water makes it relatively easy to calculate the pH and pOH of their solutions (Example 13.3). 

J 4 Identify any precipitate that may form on mixing two given solutions (Example 1.2). 

Calculate the pH change when acid or base is added to a buffer solution (Example 1 1.2). 

The properties of alloys are affected by their composition and structure. Not only is the crystalline structure important, but the size and texture of the individual grains also contribute to the properties of an alloy. Some metal alloys are one-phase homogeneous solutions. Examples are brass, bronze, and the gold coinage alloys. Other alloys are heterogeneous mixtures of different crystalline phases, such as tin-lead solder and the mercury-silver amalgams used to fill teeth. 

Solution Example 4.5 was a reverse problem, where measured reactor performance was used to determine constants in the rate equation. We now treat the forward problem, where the kinetics are known and the reactor performance is desired. Obviously, the results of Run 1 should be closely duplicated. The solution uses the method of false transients for a variable-density system. The ideal gas law is used as the equation of state. The ODEs are... 

Solution Example 7.10 found AG/ = 83,010 J. Equation (7.29) gives Kthermo = 2 xl0 SO that equilibrium at 298.15 K overwhelmingly favors ethylbenzene. Suppose the ideal gas assumption is not too bad, even at this low temperature (7 (, = 617K for ethylbenzene). The pressure is 0.5066 bar and p = 1. The reaction has the form A —> B + C so the reaction coordinate formulation is similar to that in Example 7.13. When the feed is pure ethylbenzene, Equation (7.31) becomes... 

Solution Example 8.1 laid the groundwork for this case of laminar flow without diffusion. The mixing-cup average is... 

Solution Example 11.5 treats a system that could operate indefinitely since the liquid phase serves only as a catalyst. The present example is more realistic since the liquid phase is depleted and the reaction eventually ends. The assumption that the gas-side resistance is negligible is equivalent to assuming that a = ag throughout the course of the reaction. Equilibrium at the interface then fixes a = ag/Ku at all times. Dropping the flow and accumulation terms in the balance for the liquid phase, i.e.. Equation (11.11), gives 0 = kiAiV(ag/KH - ai) - Vikafi... 

To identify the major species in any aqueous solution, first categorize the solutes. A soluble salt, strong acid, or strong base generates the appropriate cations and anions as major species. Eveiy other solute generates its molecular species in solution. In addition, H2O is always a major species in aqueous solutions. Example provides practice in identifying the major species in solution. 

Buffer capacity is determined by the amounts of weak acid and conjugate base present in the solution. If enough H3 O is added to react completely with the conjugate base, the buffer is destroyed. Likewise, the buffer is destroyed if enough OH is added to consume all of the weak acid. Consequently, buffer capacity depends on the overall concentration as well as the volume of the buffer solution. A buffer solution whose overall concentration is 0.50 M has five times the capacity as an equal volume of a buffer solution whose overall concentration is 0.10 M. Two liters of 0.10 M buffer solution has twice the capacity as one liter of the same buffer solution. Example includes a calculation involving buffer capacity. 

Inhibitors should not be present in the reagent solution. Examples are the dehydrogenase inhib-... 

Polycrystalline Material Versus Frozen Solution (Example Picket-Fence Porphyrin and Deoxymyoglobin)... 

Therapeutic fluids include crystalloid and colloid solutions. The most commonly used crystalloids include normal saline, hypertonic saline, and lactated Ringer s solution. Examples of colloids include albumin, the dextrans, hetastarch, and fresh frozen plasma. 

Alternatively, one could have calculated that after the reaction there was 2.0 M NaCl and 1.0 Af HCI in the 6.0 L of solution (Example 8.8). The ion concentrations then could have been calculated as in Example 10.13, and the results just shown would have been obtained. 

Explanatory knowledge is information that explains why things are so or why certain effects will happen. Here is where it is possible to determine the direction of the solution. Examples the way Bt proteins affect specific pest and beneficial insects what are the main reasons for unwelcome erosion effects mechanisms of vertical gene flow mechanisms of resistance development. 

For reactants (sohd or liquid), which are not sufficiently soluble in water, additional cosolvents can be used in order to obtain a homogeneous solution. Examples are alcohols, such as ethanol or 2-propanol,... 

Figure 3.39. Widespread property upgrading and additive solution examples...

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