Oxidation of n-Alkanes

Figure 12. Regioselectivity in the oxidation of n-alkanes by t-ButOOH on FePcY [57].

Partial anodic oxidation of n-alkanes on a smooth Pt electrode in CF3COOH gives isomeric sec-alkyl trifluoroacetates in 50-80% yield.118... 

The gaseous oxidation of n-alkanes can, in suitable circumstances, yield substantial amounts of O-heterocycles of the same carbon number as the initial hydrocarbon. A comparative study has been carried out of the formation of O-heterocyclic products during the combustion of n-butane, n-pentane, and n-hexane. The way in which the yields of such compounds vary with reaction conditions has been investigated. As a result of the optimization of the amounts of O-heterocycles it has been possible to obtain maximum yields of these compounds of up to 30% from n-pentane but only about 10% from n-butane and n-hexane. An attempt is made to account for the observed differences in the amounts and nature of the O-heterocyclic products formed from the three n-alkanes. 

Manganese(III) acetate is poorly reactive with saturated hydrocarbons.514 However, oxidation of adamantane by Mn(OAc)3 in trifluoroacetic acid gives relatively high yields of 1-adamantyl trifluoroacetate, showing a preferential attack at tertiary C—H bonds.515 Oxidation of n-alkanes by air in the presence of manganese catalysts constitutes the basis for an industrial process for the manufacture of synthetic fatty acids from n-alkanes of petroleum origin, which has been commercially developed in the Soviet Union.516... 

The Bashkirov oxidation (liquid-phase oxidation of n-alkanes or cycloalkanes in the presence of boric acid and hydrolysis) yields the corresponding secondary alcohols [16, 17]. The reaction is used industrially for oxidation of C10 to C18 n-alkanes, providing raw materials for detergents and for oxidation of cyclododecane to cyclo-dodecanol as an intermediate for the production of Nylon 12 (Table 1, entry 8). The process is not of much commercial importance in the western world, however. Oxidation in the absence of boric acids usually leads to mixtures of alcohols, ketones, and carboxylic acids (Table 1, entry 9). 

Oxidation of n-alkanes is stroi y exothermic, the production of 1 kg biomass liberating 27,100 k Joules. Cooling costs to maintain temperatures at about 30°C are considerable. 

Oxidation of n-alkanes by Co acetate in acetic acid occurs with a remarkable regioselectivity (rs) at the alkyl acetate as the major product in anaerobic conditions, and 2-alkanone in the presence of oxygen (equations 233 and 234). Cyclohexane is readily oxidized in nitrogen by Co(OAc)3 in acetic acid to mainly cyclohexyl acetate and 2-acetoxycyclo-hexanone. In the presence of oxygen and a high cobalt concentration, adipic acid is the major product formed (equation 235). Oxidation of adamantane by Co(OAc)s and TFA in AcOH preferentially occurs at the tertiary positions, producing 1-adamantyl acetate as the major product. ... 

Anodic oxidation of n-alkanes in acetonitrile results in mixtures of A -s-alkylacetamides but skeletal rearrangement of the intermediate i-carbenium ions is not observed. Aromatic compounds can undergo direct acetamidation in the ring. Thus, acetophenone, which normally undergoes electrophilic aromatic substitution at the meta position, affords the o- and p-acetamides (Scheme 44). Anthracene is cleanly converted into the acetamide (84) when the reaction is performed in the presence of TFAA as water scavenger (equation 41). ... 

Turn-over numbers are lower than those observed for the oxidation of n-alkanes over FePcY [12] but they have the same order of magnitude than those observed for the oxidation of cyclohexane and adamantane over FePcVPI-5 [21],... 

Alkanes collected over a 12 months period, offshore from Louisiana and Florida, were characterised by Ledet and Laseter (1974) unexpectedly, methyl branched alkanes ranging in chain length from C15 to C3S and cycloalkanes were frequently the dominant components. Possible explanations for this enrichment may be selective removal by autoxidation, preferential oxidation of n-alkanes by bacteria, adsorption onto particles, a contribution from some crude oils particularly rich in methylalkanes or a contribution from certain plants containing large quantities of 3-methyl branched alkanes (Weete et ed., 1971). 

Table 4. Oxidation of n-alkanes with different chain length over FePcY, with 1 Pc per unit cell (ferrocene method) (refs. 23,48,49) after 2 hours of reaction at 298 K with 2.4 mmol of tButOOH, 6 mmol of n-alkane, 8 micromole of FePc and 1.5 ml of dichloromethane.

Table 4.3. Oxidation of n-alkanes over MAPOs primary selectivity...

Clark, D.B., Fleischmaim, M. and Fletcher, D. (1973) The partial anodic oxidation of n-alkanes in acetonitrile and trifluoroacetic acid. Journal of the Chemical Society, Perkin Transactions 2, 1578. 

Fig. 7.7 Schematic of the lumped scheme developed in Ranzi et al. (1995) for the primary oxidation of n-alkanes. Reproduced from Ranzi et al. (1995) with permission from Elsevier...

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