Another interesting example

When AgCl(s) dissolves in aqueous NH3, two equilibria are set up and both will be simultaneously satisfied. They are  

This is a very large value for the equilibrium constant for the complexing effect of NH3(aq) on 

The experimental observation is the dissolution of the solid AgCl in the NHsfaq) which continues until equilibrium is established. This overall process is  

K is a composite equilibrium constant describing the simultaneous setting up of the two equilibria defined above. 

The standard procedures can now be used to enable the solubility of AgCl(s) in aqueous NH3 to be found for any given stoichiometric concentration of NH3(aq). 

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There are, however, a number of well-known systems in which heat effects definitely cannot be ignored. Examples include absorption of ammonia in water, dehumidification of air with concentrated H9SO4, absorption of HCl in water, and absorption of SO3 in H9SO4. Another interesting example is the absorption of acetone in water, in which the heat effec ts are mild but not neghgible. 

Another interesting example is found in the morpholine enamine of 2- -propylcyclohexanone (138), which consists of a 2 3 mixture of tri- and tetrasubstituted isomers. The radical ion from the tetrasubstituted isomer loses an ethyl radical, giving the base peak at m/e 180. 

Another interesting example for the formation of a porphyrin from a macrotetracycle is the conversion of nickel octadehydrocorrins into nickel porphyrins 15. Protonation or alkylation of 1-methyloctadehydrocorrins 11, followed by ring opening to a bilene system 12, recyclization... 

Another interesting example is the melt crystallization of s-PS. For the case of rapid cooling from the melt, the hexagonal a form is obtained [7-9], while for low cooling rates or for isothermal crystallizations, the crystalline form which is... 

Another interesting example is provided by the phenylethynylcarbene complex 173 and its reactions with five-, six-, and seven-membered cyclic enamines 174 to form bridgehead-substituted five-, six-, and seven-membered cycloalkane-annelated ethoxycyclopentadienes with high regioselectivity under mild reaction conditions (Scheme 38) [119,120]. In these transformations the phenylethynylcarbene complex 173 acts as a C3 building block in a formal [3+2] cycloaddition. Like in the Michael additions (reaction route F in Scheme 4), the cyclic electron-rich enamines 174 as nucleophiles attack the... 

Another interesting example of the use of the diode array detector to confirm the integrity of an eluted peak is afforded by an application published by the Perkin Elmer Corporation showing the separation of a mixture of aromatic hydrocarbons. The separation they examined is shown in figure 10. 

Another interesting example of the use of solid state extraction cartridges is the determination of the tricyclic antidepressant drugs in blood serum (2). 

The isomerization takes place because the excited states, both 5i and T, of many alkenes have a perpendicular instead of a planar geometry (p. 311), so cis-trans isomerism disappears upon excitation. When the excited molecule drops back to the So state, either isomer can be formed. A useful example is the photochemical conversion of c/s-cyclooctene to the much less stable trans isomer." Another interesting example of this isomerization involves azo crown ethers. The crown ether (5), in which the N=N bond is anti, preferentially binds NH4, Li, and Na, but the syn isomer preferentially binds and Rb (see p. 105). Thus, ions can be selectively put in or taken out of solution merely by turning a light source on or off." ... 

Figure 2a shows a schematic phase diagram for lyotropic liquid crystals. This figure shows the formation of micelles, cubic phases, bicontinuous cubic phases, and lamellar phases as the concentration of surfactant increases. Also shown in this figure is a schematic diagram of an ordered bicontinuous cubic phase (Fig. 2b). Another interesting example in...

Another interesting example is SHMT. This enzyme catalyzes decarboxylation of a-amino-a-methylmalonate with the aid of pyridoxal-5 -phosphate (PLP). This is an unique enzyme in that it promotes various types of reactions of a-amino acids. It promotes aldol/retro-aldol type reactions and transamination reaction in addition to decarboxylation reaction. Although the types of apparent reactions are different, the common point of these reactions is the formation of a complex with PLP. In addition, the initial step of each reaction is the decomposition of the Schiff base formed between the substrate and pyridoxal coenzyme (Fig. 7-3). 

Another interesting example of the fission of non-activated C—C bond with the liberation of carbon dioxide is the decarboxylation of oxalate. The enzymes related to degradation of oxalate have a number of potential apphcations especially in relation to diagnosis and human health. Also, the reaction mechanism of this enzyme is interesting. It requires metal ions to activate the substrate and this might give some hints to develop decarboxylation reactions of other types of compounds. In this way, the future extension is expected in this area. 

Another interesting example of dehydrative C-C coupling involves the alkylation of benzimidazole 36 with allyl alcohol 37, which is catalysed by complex 39 [15], The reaction is believed to proceed by alkene complex formation with the allyl alcohol 37 with loss of water from the NH proton of the NHC ligand and OH of the allyl alcohol to give an intermediate Ji-allyl complex. The initially formed 2-allylbenzimidazole isomerises to a mixture of the internal alkenes 38 (Scheme 11.9). 

Another interesting example of aurophilic interactions influencing electronic excited state properties is the unusual photochemical cis to trans conversion observed in dinudear goldhalide bis(diphenylphosphino)ethylene complexes, Au2X2(dppee)... 

Circular dichroism (CD) is another interesting example of an optical property of the small Au SR clusters. Since the first observation of Schaaff et al. [23,24], several reports have appeared regarding the CD activities of gold clusters protected by chiral thiols such as penicillamine [25] and A-isobutyryl-cysteine [26]. Figure 11 shows the CD spectra of 1-9, which is a good reproduction of the original report by Whetten s group [23,24]. 

Another interesting example of a reaction without additional organic radical trap has very recently been reported by Barrero and his group [48]. 

In their approach towards novel antitumor agents, Danishefsky and coworkers [22] recently published another interesting example of a domino Diels-Alder/retro-Diels-Alder reaction. These authors were attracted by the 14-membered resor-cinylic macrolide radicol (4-67) which inhibits the Hsp90 molecular chaperone [23,... 

The state provides another interesting example of how to form an inversion. As was discussed earlier, the (2,0) state actually supports a bound... 

Another interesting example is the supportation of Noyori s catalyst family containing Ru-chiral BINAP and chiral 1,2-diphenylethylenediamine [96]. These catalysts are suitable for the enantioselective hydrogenation of a variety of sub-... 

Another interesting example of a photochemi-cally induced domino process is the combination of the photocyclization of aryl vinyl sulfides with an intramolecular addition as described by Dittami et al. [901 as intermediate a thiocarbonyl ylide can be assumed. The domino-Norrish I-Knoevenagel-allyl-silane cyclization developed by us allows the efficient stereoselective formation of 1,2-trans-subsituted five- and six-membered carbocycles.1911 A photochemical cycloaddition of enamino-aldehydes and enamino-ketones with the intermediate formation of an iminium salt followed by addition to allylsilanes gives access to novel bicyclic heterocy-des. New examples of photochemically induced... 

Another interesting example of the application of sugars in the synthesis of bioactive compounds was presented by Nicotra s group.61 In this approach fructose was used as the starting material for the preparation of a series of GABA ligands, having a considerable therapeutic potential (Fig. 45). 

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