Higher alkanes

Protonated methane (CH ) does not violate the octet rule of carbon. A bonding electron pair (responsible for covalent bonding between C and H atoms) is forced into sharing with the proton, resulting in 2 electron-3 center bonding (2e-3c) (see Chapter 10). Higher alkanes are protonated similarly. 

Higher alkanes having unbranched carbon chains are like butane most stable m then-all anti conformations The energy difference between gauche and anti conformations is similar to that of butane and appreciable quantities of the gauche conformation are pres ent m liquid alkanes at 25°C In depicting the conformations of higher alkanes it is often more helpful to look at them from the side rather than end on as m a Newman projec tion Viewed from this perspective the most stable conformations of pentane and hexane... 

Section 3 3 Higher alkanes adopt a zigzag conformation of the carbon chain m which all the bonds are staggered... 

The same principles just developed for butane apply to pentane, hexane, and all higher alkanes. The most favorable conformation for any alkane has the carbon-carbon bonds in staggered arrangements, with large substituents arranged anti to one another. A generalized alkane structure is shown in Figure 3.10. 

The two propagation steps shown above for X2 are those that lead directly to the principal products (RX and HX), but many other propagation steps are possible and many occur. Similarly, the only termination step shown is the one that leads to RX, but any two radicals may combine. Thus, products like H2, higher alkanes, and higher alkyl halides can be accounted for by steps like these (these are for... 

Two reaction sequences are involved in the bacterial degradation higher -alkanes ... 

There is evidence for the anaerobic degradation of alkanes to COj, plausibly under conditions of sulfate reduction. In experiments with sediment slurries from contaminated marine areas, was recovered from " C-hexadecane (Coates et al. 1997), and was inhibited by molybdate that is consistent with the involvement of sulfate reduction. Under sulfate-reducing conditions was produced from C[14,15]octacosane (CagHjg) (Caldwell et al. 1998). Different mechanisms have been elucidated for the anaerobic degradation of higher alkanes, and both occurred simultaneously in a sulfate-reducing consortium (Callaghan et al. 2006) ... 

A non-acidic isomerization catalyst system has unexpectedly emerged from recent studies by French workers [4] in the area of Mo-oxycarbides. Although at an early stage of development, these new materials exhibit high selectivities for the isomerization of paraffins such as n-heptane. An alternative non-carbenium ion mechanistic route to achieve isomerization of higher alkanes could potentially overcome some of the limitations of conventional solid acid based catalyst systems. 

In fact, the selective catalytic removal of NO in presence of excess oxygen remains a challenge. Most of the cunent studies involve C1-C4 hydrocarbons as reductants and zeolites as catalysts, among which Cu-exchanged MFI zeolites are considered as one of the most active [2]. The reductant shows a complex influence in this reaction it has been thus reported that a Cu/Zr02 catalysts are active with pro-pene but show low activity with propane as reductant [3]. For a practical use reduction by higher alkanes would be attractive, siiKe it would be easier to handle in a vehicle. 

It is well known also that higher alkanes suffer radical gas phase oxidation above 723 K. Therefore, their use requires catalysts active and selective for deNOx at lower temperatures. The mechanism of NOx elimination is still debated a redox mechanism involving Cu ions is probable, and isolated Cu cations exchanged into MFI [4,5] or mordenite [6] have been found to be more active than CuO clusters. It must be emphasized, however, that acid zeolites exhibit good activity at high temperature, and acid mechanisms have been proposed [7-10]. In presence of Cu this acid mechanism disappears probably due to the decrease of the acidity of mordenite upon Cu exchange [6]. According to... 

Firstly, the difference between ethane and higher alkanes cannot be readily explained by mechanisms such as those proposed by Gault (Scheme 38) or 1,2-carbon-carbon activation mechanisms (Scheme 39), while the mechanism involving y-H activation does fully account for this observation. Given... 

In the hydrogenolysis of the higher alkanes on the nonnoble group VIII metals (i.e., iron, cobalt, and nickel), the mode of cracking is very different from that observed on the noble metals of group VIII (49, 50). On nickel,... 

Poly(nHAMCL)s From Higher Alkanes and Alkanoic Acids. 60... 

Chlorination of most of higher alkanes gives a mixture of isomeric monochloro products as well as more highly halogenated compounds. 

In addition, a higher alkane can eliminate a lower one as follows ... 

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