Alkanes acid-base chemistry

Chapters 1—10 begin a study of organic compounds by first reviewing the fundamentals of covalent bonding, the shapes of molecules, and acid-base chemistry. The structures and typical reactions of several important classes of organic compounds are then discussed alkanes, alkenes and alkynes, haloalkanes, alcohols and ethers, benzene and its derivatives, and amines, aldehydes, and ketones, and finally carboxylic acids and their derivatives. 

A more detailed interpretation of the chemistry of catalytic cracking was based on studies with pure hydrocarbons.121-123 A simplified summary put forward by Heinemann and coworkers123 (Fig. 2.1) shows how Cg open-chain and cyclic alkanes are transformed to benzene by the action of both the hydrogenating (metal) and acidic (halogenated alumina) functions of the catalyst. 

The initial coordination of reactants has indeed been proposed to explain the selective oxidation of alkenes in the presence of saturated hydrocarbons. It was argued that, owing to the hydrophobic nature of titanium silicates, the concentration of both hydrocarbons inside the catalyst pores is relatively high and hence the alkenes must coordinate to TiIv. Consequently, the titanium peroxo complex will be formed almost exclusively on Tilv centers that already have an alkene in their coordination sphere, and will therefore oxidize this alkene rather than an alkane which may be present in the catalyst (Huybrechts et al., 1992). Objections to this proposal are based on the fact that the intrinsically higher reactivity of alkenes with respect to saturated hydrocarbons is sufficient to account for the selectivity observed (Clerici et al., 1992). But coordination around the titanium center of an alcohol molecule, particularly methanol, is nevertheless proposed to explain the formation of acidic species, as was previously discussed. In summary, coordination around Tiiv could play a more important role than it does in solution chemistry as a consequence of the hydrophobicity of the environment where the reactions take place. 

Alkynes also undergo a reaction that has no analogy in alkene chemistry. Because a C - H bond of an alkyne is more acidic than a C - H bond in an alkene or an alkane, alkynes are readily deprotonated with strong base. The resulting nucleophiles react with electrophiles to form new carbon-carbon o bonds, so that complex molecules can be prepared from simple starting materials. The study of alkynes thus affords an opportunity to learn more about organic synthesis. 

The nomenclature of FA reflects the long history of their smdy and description. Most FA were originally described under trivial names prior to the adoption of the international molecular nomenclature rules in 1892 (Table 3.1). Even after adopting the International Union of Pure and Applied Chemistry (lUPAC) system for nomenclature (lUPAC-IUB, 1977), the habit of assigning trivial names to FA continues. The basis of the systematic nomenclature system is an extension of that accepted for hydrocarbon (alkane/alkene) naming. Hence, the descriptive name is based on the number of carbon atoms contained in the molecule, with the suffix -e replaced with -oic acid. However, in most instances, FA are referred to by their formula notations. As is the case with systematic and trivial names, there exists an lUPAC accepted formula notation nomenclature and several earher versions (Table 3.2). Each system... 

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