Hydrocarbons from alkenes

Radical cations can be derived from aromatic hydrocarbons or alkenes by one-electron oxidation. Antimony trichloride and pentachloride are among the chemical oxidants that have been used. Photodissociation or y-radiation can generate radical cations from aromatic hydrocarbons. Most radical cations derived from hydrocarbons have limited stability, but EPR spectral parameters have permitted structural characterization. The radical cations can be generated electrochemically, and some oxidation potentials are included in Table 12.1. The potentials correlate with the HOMO levels of the hydrocarbons. The higher the HOMO, the more easily oxidized is the hydrocarbon. 

Hydrocarbons lacking directing substituents are not very reactive toward metal-lation, but it has been found that a mixture of n-butyllithium and potassium r-butoxide66 is sufficiently reactive to give allyl anions from alkenes such as isobutene.67... 

In addition to separating product from catalyst, excess ligand and reaction solvent, one must also separate byproducts arising from the reactants or products. For example in hydroformylation, one must separate saturated hydrocarbon, isomerized alkene and aldehyde dimers and trimers. 

This effect of adding HC1 to the reaction cell has been used to advantage in distinguishing alkanes from alkenes and oxygenated hydrocarbons in a GC detector utilizing active nitrogen [56],... 

One may inquire whether the evidence that 77-allyl complexes yield desorbed olefins when formed from dienes and hydrogen, or from alkenes, is pertinent to the question concerning the course of the exchange of such complexes formed by the adsorption of saturated hydrocarbons. The composition of the surface must be different under the two circumstances in one there must be few sites not occupied by olefin or half-hydrogenated intermediates, while in the other (the exchange of saturated hydrocarbons) many sites must be vacant. Consequently, in the absence of an excess of any unsaturated hydrocarbon, there is no driving force for the desorption (or displacement) of the unsaturated intermediates which are formed on the surface and intermediates of any degree of unsaturation remain bonded to the surface and leave it only as saturated hydrocarbon. Yet the evidence obtained from the reactions of the unsaturated hydrocarbons must indicate the paths which may be traversed under either circumstance. 

Silver ions form similar alkene complexes which are soluble in aqueous solution and may be used to effect the separation of unsaturated hydrocarbons from alkanes. Catalysis for the polymerization of alkenes also form metal-alkene complexes which lead to polymerized product. 

The hydrocarbon groups derived from alkenes have the suffix -enyl, as in alkenyl, and numbering of the group starts with the carbon atom attached to the main chain ... 

Kerosine, boiling point 180° to 230°, contains hydrocarbons from C to C12. Much of this fraction is utilized as jet engine fuels or is cracked to simpler alkanes (and alkenes). 

The ability of insects to withstand desiccation was recognized in the 1930s to be due to the epicuticular layer of the cuticle. Wigglesworth (1933) described a complex fatty or waxy substance in the upper layers of the cuticle which he called cuticulin . The presence of hydrocarbons in this wax of insects was suggested by Chibnall et al. (1934) and Blount et al. (1937), and over the next few decades the importance of hydrocarbons in the cuticular wax of insects was established (Baker et al., 1963 and references therein). The first relatively complete chemical analyses of the hydrocarbons from any insect, the American cockroach, Periplaneta americana (Baker et al., 1963), occurred after the development of gas-liquid chromatography (GLC). The three major components of the hydrocarbons of this insect, //-pen taco sane, 3-methylpentacosane and (Z,Z)-6,9-heptacosadiene, represent the three major classes of hydrocarbons on insects, n-alkanes, methyl-branched alkanes and alkenes. Baker and co-workers (1963) were able to identify n-pentacosane by its elution time on GLC to a standard and its inclusion in a 5-angstrom molecular sieve. 3-Methylpentacosane... 

Looked at as a polymer, rubber is made up of C5 units joined together by C-C bonds. We should naturally expect to make a hydrocarbon polymer from alkenes, so if we separate these C5 units we find that they are dienes rather than simple alkenes. if you have read Chapter 51, they might be familiar to you as the isoprene units from which terpenes were originally supposed to be made. 

The formyl cation HCO+ (vco at 2110 cm ) is generated from CO under pressure in the presence of HF/SbFs. Concentrated sulfuric acid or the HCl/CuCl system, activates carbon monoxide toward the electrophilic attack on aromatic hydrocarbons to form aromatic aldehydes (Gatterman-Koch reaction). Branched carboxylic acids are obtained from alkenes and CO in the presence of concentrated sulfuric acid (Koch process) (equation 3). ... 

Aromatic Hydrocarbons and Light Alkanes. Carbonaceous chondrites contain a wide range of aromatic hydrocarbons, from benzene through alkylbenzenes and -naphthalenes to polynuclear hydrocarbons of up to six fused benzene rings (see the reviews cited above). At higher carbon numbers, aromatics tend to be less abundant than normal alkanes, but below about C j, the reverse is true (Fig. 3, top). In fact, virtually no normal alkanes at all are found between and Cg, their place having been taken largely by benzene, toluene, xylene, and various alkenes or branched alkanes, notably butene (Studier et al., 1965 b, 1968, 1972 Hayes and Biemann, 1968 Levy et al., 1973). ... 

The natiue of the higlier-molecular-weight aliphatic hydrocarbons from the Murchison has been controversial. Kvenvolden et al. [33] detected a wide variety of coeluting isomers dominated by polycyclic aliphatic structures. Oro el al. [41] reported Cg to Cis metliyl and dimetliyl alkanes, alkenes, and cycloalkanes. Studier et al. [42] detected straight-chain alkanes with some isoprenoidal hydrocarbons. It is now widely believed that straight-chain alkanes were the dominant components of the ahphatic fraction in the solar nebula. However, Cronin and Pizzarello [43] analyzed organic materials from the Murchison under less environmental contamination and concluded lliat tire n-alkanes, methyl alkanes, and isoprenoid alkanes reported in the Murchison were terrestrial contaminants. Tliese authors identified Cis to C30 cyclic alkanes as the major indigenous alipliatic components. 

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