Simple Alkanes

No other class of natural organohalogens has the wide diversity of sources, as do the simple halokanes - marine, terrestrial biogenic, terrestrial abiotic, biomass combustion, and volcanoes. However, since the previous survey, only a few newly discovered natural simple halogenated alkanes have been reported. 

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Rabinovitch B S and Setser D W 1964 Unimolecular decomposition and some isotope effects of simple alkanes and alkyl radicals Adv. Photochem. 3 1-82... 

The tliird part is tire interaction between tire tenninal functionality, which in tire case of simple alkane chains is a metliyl group (-CH ), and tire ambient. These surface groups are disordered at room temperature as was experimentally shown by helium atom diffraction and infrared studies in tire case of metliyl-tenninated monolayers [122]. The energy connected witli tliis confonnational disorder is of tire order of some kT. 

Instead of radical reactions, models based on molecular reactions have been proposed for the cracking of simple alkanes and Hquid feeds like naphtha and gas oil (40—42). However, the vaUdity of these models is limited, and caimot be extrapolated outside the range with confidence. With sophisticated algorithms and high speed computers available, this molecular reaction approach is not recommended. 

The chemical resistance of polyethylene is, to a large measure, that expected of an alkane. It is not chemically attacked by non-oxidising acids, alkalis and many aqueous solutions. Nitric acid oxidises the polymer, leading to a rise in power factor and to a deterioration in mechanical properties. As with the simple alkanes, halogens combine with the hydrocarbon by means of substitution mechanisms. 

ThomsonN r Click Organic Interactive to learn to write IUPAC names for simple alkanes. 

Aliphatic (Section 3.2) A nonaromalic hydrocarbon such as a simple alkane, alkene, or alkyne. 

Physical Properties of Simple Alkanes, Alcohols, and Ethers... 

It is by means of successive reactions of this sort that simple alkanes like methane and ethane give rert-butyl cations in super acid solutions (p. 219). °... 

C12H25LC12X), silanes (Ci8H37SiH3), and simple alkanes (CioH22). The experimental procedure for the digestive ripening process with different ligands is detailed below. 

There is some increase in selectivity with functionally substituted carbenes, but it is still not high enough to prevent formation of mixtures. Phenylchlorocarbene gives a relative reactivity ratio of 2.1 1 0.09 in insertion reactions with i-propylbenzene, ethylbenzene, and toluene.212 For cycloalkanes, tertiary positions are about 15 times more reactive than secondary positions toward phenylchlorocarbene.213 Carbethoxycarbene inserts at tertiary C—H bonds about three times as fast as at primary C—H bonds in simple alkanes.214 Owing to low selectivity, intermolecular insertion reactions are seldom useful in syntheses. Intramolecular insertion reactions are of considerably more value. Intramolecular insertion reactions usually occur at the C—H bond that is closest to the carbene and good yields can frequently be achieved. Intramolecular insertion reactions can provide routes to highly strained structures that would be difficult to obtain in other ways. 

The chain length, i.e. number of RH —> RC1 conversions per Cl produced by photolysis, is wlO6 for CH4, and the reaction can be explosive in sunlight. Chlorination can also be initiated thermolytically, but considerably elevated temperatures are required to effect Cl2 — 2C1, and the rate of chlorination of C2H6 in the dark at 120° is virtually indetectable. It becomes extremely rapid on the introduction of traces of PbEt4, however, as this decomposes to yield ethyl radicals, Et, at this temperature, and these can act as initiators Et- + Cl—Cl —> Et—Cl + Cl. Chlorination of simple alkanes such as these is seldom useful for the preparation of mono-chloro derivatives, as this first product readily undergoes further attack by the highly reactive chlorine, and complex product mixtures are often obtained. 

Figure 4.1 Ball-and-stick models for three simple alkanes.

The first structural study of a UPD layer involved the formation of a series of Agl monolayers on Pt(lll) single crystals [132, 133], Pt is the quintessential catalytic metal, and thus reacts with almost any organic compound, other than simple alkanes [134], in other words, it is easily contaminated. In the early days of UHV-EC studies, contamination during transfer of Pt single crystals from the analysis chamber to the electrochemical cell and back was the chief stumbling block to well-defined studies of... 

Iridium hydride complexes effectively catalyze addition of nitriles or 1,3-dicarbonyl compounds (pronucleophiles) to the C=N triple bonds of nitriles to afford enamines.42S,42Sa Highly chemoselective activation of both the a-C-H bonds and the C=N triple bonds of nitriles has been observed (Equation (72)). To activate simple alkane dinitriles, IrHs(P1Pr3)2 has proved to be more effective (Equation (73)). The reaction likely proceeds through oxidative addition of the a-C-H bonds of pronucleophiles to iridium followed by selective insertion of the CN triple bonds to the Ir-C bond. 

Reactions of 0 with Alkanes. Bohme and Fehsenfeld (16), working in the gas phase, have shown that 0 reacts with simple alkanes by abstracting a hydrogen atom, and except for methane the efficiency of this reaction is quite high. Even in the case of methane, the reaction occurs with a reaction probability of 0.08. Surface reactions between alkanes and surface 0 ions follow a similar pathway. As indicated by a disappearance of the 0 signal, stoichiometric reactions occur at temperatures sufficient to allow the diffusion of the alkane across the surface (17). For example, most of the 0" on Mo/Si02 reacts with CH in a period of 10 min at 77K ( 2). Thus, hydrogen atom abstraction does not appear to be an activated process. 

Oxidation of sp3 Carbon-Hydrogen Bonds of Simple Alkanes... 

The naming of alkanes relies upon choosing the longest carbon chain in the structural formula. Then name the hydrocarbon branches with a number indicating to which carbon atom the branch is attached. Here are the specific rules for naming simple alkanes ... 

The preparation of thiols by nucleophilic displacement reactions using aqueous potassium or sodium hydrogen sulphide under catalytic conditions is not particularly effective. A limited number of simple alkane thiols have been obtained under mild and neutral conditions in moderate yield (70-80%) from the reaction of bis(n-butyltin) sulphide with bromoalkanes in the presence of a ca. twofold amount of tetra-n-butylammonium fluoride [1], but there has been no exploitation of this procedure. 

With the exception of adamantane and few related compounds [1-5] in which dichlorocarbene reacts at the tertiary C-H centre, the yields for the majority of insertion reactions into hydrocarbons are low and of little synthetic value (Table 7.1). Reaction also occurs in low yield at benzylic C-H sites [1, 6, 7] and, in the case of simple alkanes, the insertion reaction is promoted by alkoxy groups [1,6-14], Thus, whereas methylcyclohexane produces only 4% yield of the l-dichloromethyl-l-methylcyclohexane, the corresponding yield with 1-methoxycyclohexane is 13% [6], Similarly, the low yielding reaction of 1-methoxyadamantane with dichlorocarbene produces l-dichloromethyl-3-methoxyadamantane by insertion into the tertiary C-H site and (2,2-dichioroethoxy)adamantane by reaction at the primary C-H site, which is activated by the methoxy group. No reaction occurs at the secondary C-H sites [2],... 

Some Schrock-type carbene complexes, i.e. high-valent, electron-deficient, nucleophilic complexes of early transition metals, can undergo C-H insertion reactions with simple alkanes or arenes. This reaction corresponds to the reversal of the formation of these carbene complexes by elimination of an alkane (Figure 3.36). 

Let us consider first the simple alkane ethane. Since both carbons have a tetrahedral array of bonds, ethane may be drawn in the form of a wedge-dot representation. 

The catalytic behavior of small metal particles in heterogeneous catalysts varies with metallic particle size and shape a phenomenon referred as a structure-sensitivity. Simple alkanes such as ethane, propane, n-butane and isobutane can be used as archetype molecules for studying hydrogenolysis reactions as they... 

Polyolefines, like simple alkanes, can be chlorinated by chlorine giving hydrogen chloride and chlorinated products such as Tyrin, used as plasticizers and flame retardants, and poly (vinyl dichloride), which has better heat resistance than PVC and is used for hot water piping. 

For example, Figure 5.11 shows typical results from a relative rate experiment on the reaction of chlorine atoms with some simple alkanes (Beichert et al., 1995). The chlorine atoms in this case were produced by the... 

Beichert, P L. Wingen, J. Lee, R. Vogt, M. J. Ezell, M. Ragains, R. Neavyn, and B. J. Finlayson-Pitts, Rate Constants for the Reactions of Chlorine Atoms with Some Simple Alkanes at 298 K Measurement of a Self-Consistent Set Using both Absolute and Relative Rate Methods, J. Phys. Chem., 99, 13156-13162 (1995). 

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