Straight-chained hydrocarbons

Isomeri2ation of straight-chain hydrocarbons is of particular importance for lead-free gasoline. Addition of high octane aromatic hydrocarbons or olefins is questionable based on environmental considerations (77). An efficient octane enhancing additive is methyl tert-huty ether (MTBE). 

Hexane refers to the straight-chain hydrocarbon, C H branched hydrocarbons of the same formula are isohexanes. Hexanes include the branched compounds, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, and the straight-chain compound, / -hexane. Commercial hexane is a narrow-boiling mixture of these compounds with methylcyclopentane, cyclohexane, and benzene (qv) minor amounts of and hydrocarbons also may be present. Hydrocarbons in commercial hexane are found chiefly in straight-mn gasoline which is produced from cmde oil and natural gas Hquids (see Gasoline AND OTHER MOTOR fuels Gas,natural). Smaller volumes occur in certain petroleum refinery streams. 

Channels in crystals of thiourea [62-56-6] (87) are comparable but, as a consequence of the larger size of the sulfur atom, have larger cross-sectional areas (0.7 nm) and can trap branched-chain, aUcychc, and other molecules of similar dimensions including polychlorinated hydrocarbons. But they do not include the straight-chain hydrocarbons that work so well with urea. 

As an example of the chemical signihcance of the process technology, the products of die Fischer-Tropsch synthesis, in which a signihcant amount of gas phase polymerization occurs vary markedly from hxed bed operation to the fluidized bed. The hxed bed product contains a higher proportion of straight chain hydrocarbons, and the huidized bed produces a larger proportion of branched chain compounds. 

Part A of Table 1.5 shows all the acyclic C4-C6 and some of the Cg hydrocarbons. A general trend is discernible in the data. Branched-chain hydrocarbons are more stable than straight-chain hydrocarbons. For example, A/fj for -octane is —49.82 kcal/mol, whereas the most highly branched isomer possible, 2,2,3,3-tetramethylbutane, is the most stable of the octanes, with of —53.99 kcal/mol. Similar trends are observed in the other series. 

The straight-chain hydrocarbons represent just one group of straight-chain hydrocarbons, the saturated hydrocarbons known as the alkanes. There are other series of hydrocarbons that are unsaturated one of those is important in the study of hazardous materials. Additionally, the first hydrocarbon in another series is the only hydrocarbon important in that series. Each of these hydrocarbon series are briefly described below. 

The system for naming the straight-chain hydrocarbons is based on an agreed-upon method of retaining the first three or four common names, then using Greek prefixes that indicate the number of carbon atoms in the chain. For isomers, the same system is used, always using the name of the compound that is attached to the chain and the name of the chain. 

Diynes and triynes refer to alkynes containing two or three triple bonds poly-ynes contain multiple triple bonds. A conjugated triyne is a straight-chain hydrocarbon with triple bonds alternating with single bonds. An examples is... 

Normal alkanes (n-alkanes, n-paraffms) are straight-chain hydrocarbons having no branches. Branched alkanes are saturated hydrocarbons with an alkyl substituent or a side branch from the main chain. A branched... 

In a straight chain hydrocarbon, however, an alpha olefin ion is formed ... 

The most commonly used amphiphiles to build L-B hlms for tribological applications are the straight chain hydrocarbon compounds with simple functional groups such as the fatty acids, including stearic acids, arachidic acids, and behenic acids [32], but other amphiphilic molecules, e.g., 2,4-heneicosanedione and 2-docosylamina-5-nitropyridine, are also applied in some cases. There are two major systems of self-assembled monolayers, namely the alkylsilance derivatives (e.g., OTS, octadecyltrichlorosilane) on hydroxylated surfaces and the alkanethiols on metal substrates, which have been investigated extensively to examine their properties as solid lubricants and protective surface films [31 ]. 

If X is an alkyl group and Y = H, the reference compound XIII is a straight chain hydrocarbon, and the second process above consists in its transformation to a branched unit (XIV) having a single substituent. Hence... 

Most moth sex pheromones that are straight chain hydrocarbons also usually have an odd number of carbons. Most of these are polyunsaturated with double bonds in the 3,6,9- or 6,9-positions, indicating that they are derived from linolenic or linoleic acid, respectively [49,51]. Iinolenic and linoleic acid cannot be biosynthesized by moths so they must be obtained from the diet [75]. A few even chain-length hydrocarbon sex pheromones have been identified that also have 3,6,9- or 6,9-double bond configurations [49], indicating they too are derived from linolenic or linoleic acids however, it is not known how these even chain hydrocarbons are formed. 

This principle only applies to straight chain hydrocarbons and is inappropriate if other types of substances are involved (e.g., hydrogen). 

A retention index (RI) was used to allow comparison of compound retention data between columns of different equipment, e.g. GC and GC-MS. Straight chain hydrocarbons (alkanes) were assigned an index of 100 times the number of carbon atoms in the molecule. The RI s of all compounds within all the extracts were calculated by using the difference between the retention indices of the alkane eluting before and after that compound ... 

Several methodologies can be used to identify not only crude or refined product type, but also the brand, grade, and, in some instances, the source crude. The petroleum industry has yielded conventional methods for the characterization of refined products. The simplest is the routine determination of API gravity and development of distillation curves where NAPL is present. More sophisticated methods include gas chromatography and statistical comparisons of the distribution of paraffinic or n-alkane compounds between certain C-ranges. With increased degradation and decomposition, the straight-chain hydrocarbons ( -alkanes) become less... 

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