Briefly Exploring Other Reactions

Many other reactions involving aromatic systems are possible. Many of them are extensions of the reactions you learned in your first semester of organic chemistry. For example, you may have the hydrogenation reaction of a side 

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Trost et al 2 briefly explored using non-enone enophiles. Simple alkenes led to the formation of complex mixtures of isomers due to the presence of an additional set of /3-hydrogens. Many other types of substrates were incompatible with reaction conditions. Vinyl ketones were, therefore, the only coupling partners shown to be effective in the ruthenium-catalyzed Alder-ene couplings of allenes and alkenes. 

Finally, achiral phosphonium salts have been explored as Lewis acid catalysts in some other reactions. The examples are briefly listed here but are not discussed in more detail. Phosphonium salts have been used as catalysts for the N,N-dimethylation of primary aromatic amines with methyl alkyl carbonates, giving the products in good yields [78]. Furthermore, acetonyl(triphenyl)phosphonium bromide has been used as a catalyst for the cydotrimerization of aldehydes [79] and for the protection/deprotection of alcohols with alkyl vinyl ethers [80, 81). Since the pKj of the salt is 6.6 [82-85], the authors proposed that alongside to the activation of the phosphonium center, a Br0nsted add catalyzed pathway is possible. 

To keep this review to a reasonable length we had to limit our discussions to reactions of only sulfur oxyacids and their anhydrides. While we have introduced, where pertinent to the topic under discussion, results from a number of studies involving other derivatives of oxyacids of sulfur, there has been extensive work on mechanism and reactivity in reactions of some sulfur oxyacid derivatives that we have not been able to include, but of which we feel the reader should at least be aware. We will therefore indicate briefly what some of these areas are and given some leading references, so that persons wishing to do so may explore these topics on their own. 

While natural gas reforming is the primary process for the industrial production of H2, the reforming of other gaseous hydrocarbons such as ethane, propane, and n-butane have been explored for the production of H2 for fuel cells.52,97 The reforming of propane and n-butane received particular attention in recent years, because they are the primary constituents of liquefied petroleum gas (LPG), which is available commercially and can be easily transported and stored on-site. LPG could be an attractive fuel for solid oxide fuel cells (SOFCs) and PEMFCs for mobile applications.98 01 The chemistry, thermodynamics, catalysts, kinetics, and reaction mechanism involved in the reforming of C2-C4 hydrocarbons are briefly discussed in this section. 

Abstract This chapter explores the role of abiotic reactions such as acid catalysis (hydrolysis) as well as the adsorption of methyl tert-butyl ether (MTBE) and other fuel oxygenates in environmental issues as the remediation of these substances is notoriously difficult. First of all, these methods are briefly classified with other abiotic technologies. The suitability of hydrolysis and adsorption for the remediation of water contaminated by fuel oxygenates is then discussed in detail, with information being provided about the principle of the reactions, potential catalysts and sorbents, limitations of the reactions, and practical implications. To conclude, the possible application of hydrolysis and adsorption in combination with other remediation techniques is also examined. 

In the remaining sections of this chapter, the physical and host properties of CB[n] as they relate to their apphcations as nanoreactors will be discussed in detail, and a detailed representative survey of the specific types of reactions which have been templated or catalyzed by them will be presented. This is not intended to be a comprehensive review, as the number of publications on CB[n] both as hosts and as nanoreactors is extensive. Furthermore, the many other various uses of CB[ ] (briefly described previously) for the formation of rotaxanes and other interlocked species, self-assembled capsules and adducts, and in drug dehvery, as inhibitors of reactions, and as components of nanomachines and nanostructures, will not be covered. This chapter will, in a nutshell, explore the uses of CB[ ] as nanosize reaction flasks. 

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