Alkane Chemistry

The alkanes have low reactivities as compared to other hydrocarbons. Much alkane chemistry involves free-radical chain reactions that occur under vigorous conditions, eg, combustion and pyrolysis. Isobutane exhibits a different chemical behavior than / -butane, owing in part to the presence of a tertiary carbon atom and to the stability of the associated free radical. 

The combustion of alkanes, the concentration of atmospheric carbon dioxide, and global warming (Section 4.14B) An introduction to lipids, biomolecules whose properties can be explained by understanding alkane chemistry cholesterol in the cell membrane (Section 4.15)... 

There are frequently available aromatic compounds containing aliphatic side chains that are not simple alkyl groups. An alkylbenzene can be prepared from one of these compounds by converting the side chain into an alkyl group. Although there is an aromatic ring in the molecule, this conversion is essentially the preparation of an alkane from some other aliphatic compound. The methods used are those that we have already learned for the preparation of alkanes hydrogenation of a carbon carbon double bond in a side chain, for example. Many problems of the alkylbenzenes are solved by a consideration of simple alkane chemistry. 

One of the possible reasons for that is our insufficient understanding of light alkane chemistry and, consequently, our limited capability to develop efficient technologies. First of all, petrochemistry dominates not only in industry, but also in prevailing scientific and technical approaches. However, if we analyze the production of the same final products (for instance, liquid motor fuels) from... 

Atmospheric Photooxidation of Propane To illustrate alkane chemistry, consider the atmospheric photooxidation of propane ... 

In connection with the activation of saturated hydrocarbons via homogeneous catalysis, we have examined transition metal catalyzed reactions of various strained hydrocarbon systems that have unique steric and electronic properties. Strained carbon-to-carbon single bonds have considerable TT-bonding character. The chemistry of these substrates should be intermediate between well-documented transition metal chemistry of alkenes and rather unclarified alkane chemistry (1, 2, 3). Our attention has been focused particularly on the stereoselectivity, regioselectivity, and periselec-tivity of the Ni(0)-catalyzed reactions (4-14). 

Important work by Chen et al. [123b] has shown how borylation of alkanes can be achieved both photochemically and thermally from diboron reagents to give alkylboranes (Eq. 2.43). The best catalysts, [CpRh(ethylene)2] and [Cp Rh(r/ -CeMce)], are active at 150°C. The B-B bond oxidatively adds to the metal probably followed by CH oxidative addition. Reductive eMmination gives rise to a new B-C bond being formed. Functionalization occurs at the terminal position of a linear alkane as in the alkane chemistry described above. Since C-B bonds are in principle precursors to a wide variety of functional groups, this reaction has great promise for future development. 

The original work in this area was done by Dumesic et al. and involved various condensations of HMF and related molecules with acetone followed by HDO to give Ci-Ci5 alkanes (for example, 1—>17+19) (Scheme 6) [100]. Liu and co-workers recently described the benzoin condensation of HMF to give a dimer that could be submitted to HDO to give C10-C12 alkanes [101]. Sutton and co-workers likewise employed simple aldol chemistry between HMF and acetone to access C9-C15 hydrocarbons [102]. This sugar derivative to alkane chemistry has been successfully piloted by the startup company Virent [103],... 

The properties of the alkanes, both acyclic and cyclic, are so well ordered and classified in terms of atomic and group contributions that the use of the theory of atoms in molecules as the basis for the theoretical discussion of alkane chemistry is most appropriate. The theory, in addition to predicting these properties from fundamental principles, leads directly to an understanding of their additive and constitutive nature. 

Alkanes are relatively stable species thermodynamically and so many reactions of alkanes (dehydrogenation, dehydrodimerization, carbonylation) are unfavorable under ambient conditions. This means we often need to couple some favorable process with the unfavorable alkane conversion in order to drive it. We look at the details in Section III.B, but only note here that the common appearance of photochemistry in alkane chemistry can be seen as a way to drive reactions thermodynamically and to access highly reactive transition metal fragments that are kinetically competent to react with alkanes. 

Very recently, this reaction has been used for synthetic alkane chemistry on a multigram scale at ambient temperatures and pressures. For example, cyclooctane can be converted to the dimer in high yield even at high conversion. This would not have been the case in a solution phase radical reaction, because the product R2 is intrinsically more reactive than the initial substrate, RH. The reason for the selectivity proved to be that the dimer has so low a vapor pressure that essentially only the original substrate, cyclooctane, is present in the vapor phase and reaction only happens in the vapor. This vapor selectivity effect allows the initial functionalization product to be isolated . 

Whilst solid acids such as zeolites and other aluminosilicates have been the subject of considerable study in the context of alkane chemistry (e.g. catalytic cracking and alkene isomerisation), the design of more versatile materials which can be used in the fine chemical industry has been less thoroughly researched. However, the need for the production of solid acids to replace traditional protonic acids such as hydrogen fluoride, phosphoric and sulfuric acids in liquid phase processes is an increasingly important goal. Some progress has been made in this area and the commercial product Envirocat EPIC [19] provides an excellent example of a... 

In spite of these advances in alkane chemistry, the development of a series of robust and selective catalysts for different alkane conversion reactions remains a continuing challenge in organometallic chemistry today. Another related and very challenging problem is C—F activation in perfluorocarbons. 

Opportunities for alternative raw materials applying homogeneous transition metal catalysis can be seen in synthesis gas chemistry, alkane chemistry, and CO2 chemistry. 

The atmospheric behavior of the simple aliphatic ethers, to a first approximation, mirrors that of the alkanes. Reaction with OH is the dominant removal pathway, and occurs via abstraction of an H-atom. In general, however, the ethers are more reactive than the alkanes, as the ether linkage leads to a weakening of the neighboring C—H bonds, and thus imparts an activation effect on the OH reaction. The major oxidation steps occurring subsequent to abstraction are also similar to those occurring in atmospheric alkane chemistry, involving the formation of a peroxy radical and an alkoxy... 

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