Branched chain alkane Saturated hydrocarbon

Bragg, William H., 248 Branched chain alkane Saturated hydrocarbon in which not all the carbon atoms are in a single continuous chain, e.g., C—C—C, 580... 

Separation and Sub-fractionation of Alkanes Saturated hydrocarbons were separated from the neutral oil by silica-gel (60-120 mesh, dehydrated at 150°C for 5 h) chromatography in a 1 m X 30 mm i.d. column eluted with distilled n-hexane. n-Alkanes were separated from iso-octane solutions of total alkanes by adsorption for one week on 5 X molecular sieve (freshly dehydrated for 2h h at U00°C). Washing with iso-octane, followed by Soxhlet extraction, freed the molecular sieve from inwanted non-adsorbed compo mds n-alkanes were recovered by desorption after refluxing the molecular sieve for several hours with n-hexane. For the Kuwait crude and fluidized-bed tar, the molecular-sieve treatment was preceded by urea-adduction of n-alkanes and thiourea-adduction of branched-chain alkanes. 

The hydrocarbon types found in petroleum are (i) paraffins, (ii) cycloparaffin (naphthenes or cyclohexanes), and (iii) aromatics. Paraffins range from methane to -hexacontane (C60H1225 a microcrystalline wax) of both straight- and branched-chain alkanes. Higher boiling fractions are high in saturated alkanes while commercial paraffin mainly consists of straight-chain... 

Aliphatic framework molecules most common in organic acids include alkanes (saturated hydrocarbons) and alkenes (unsaturated hydrocarbons). These saturated and unsaturated aliphatic carboxylic acids may be acyclic (straight or branched chains) or alicyclic (aliphatic rings). Acyclic aliphatic monocarboxylic acids are also referred to as fatty acids (Table 1). The first five saturated acids (formic to valeric) of this type are sometimes referred to as short-chain, low-molecular-weight, or volatile fatty acids. Although a nomenclature for these acids has been established by the International Union of Pure and Applied Chemistry (lUPAC), the convention of using the trivial names for the first five saturated acids has remained. Similarly, trivial names are used for the aliphatic dicarboxylic acids (Table 2) that are saturated with two to four carbon atoms (C2-C4) and unsaturated with four carbon atoms (C4). Alicyclic carboxylic acids contain one or more saturated or partially unsaturated rings. These acids most commonly occur... 

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... 

Alkanes are a class of saturated hydrocarbons with the general formula C H2n. -2- They contain no functional groups, are relatively inert, and can be either straight-chain (normal) or branched. Alkanes are named by a series of IUPAC rules of nomenclature. Compounds that have the same chemical formula but different structures are called isomers. More specifically, compounds such as butane and isobutane, which differ in their connections between atoms, are called constitutional isomers. 

One large and structurally simple class of hydrocarbons includes those substances in which all the carbon-carbon bonds are single bonds. These are called saturated hydrocarbons, or alkanes. In the alkanes the carbon atoms are bonded to each other in chains, which may be long or short, straight or branched. 

The chain and branched chain saturated hydrocarbons make up a family called the alkanes. Some saturated hydrocarbons with five carbon atoms are shown in Figure 18-11. The first example, containing no branches, is called normal-pentane or, briefly, n-pentane. The second example has a single branch at the end of the chain. Such a structural type is commonly identified by the prefix iso- . Hence this isomer is called /50-pentane. The third example in Figure 18-11 also contains five carbon atoms but it contains the distinctive feature of a cyclic carbon structure. Such a compound is identified by the prefix cyclo in its name—in the case shown, cyclopentane. 

Cycloalkanes are cyclic saturated hydrocarbons with the general formula C H2 . Therefore, a substance with the formula C3H8 could not be a cycloalkane, since C3H8 conforms to the general formula, C H2 +2, the molecular formula for an alkane. It is, however, too small to be a branched alkane with a methyl group attached to the longest chain. In fact, C3H8 is propane. 

Butane, is the either of two saturated hydrocarbons, or alkanes, with the chemical formula of C4H10 of the paraffin series. In both compounds the carbon atoms are joined in an open chain. In n-butane (normal), the chain is continuous and unbranched whereas in i-butane (iso) one of the carbon atoms forms a side branch. This difference in structure results in small but distinct differences in properties. Thus, n-butane melts at -138.3 °C (-216.9 °F) and boils at -0.5 °C (31.1 °F), and i-butane melts at -145 °C (-229 °F) and boils at -10.2 °C (13.6 °F). 

Our discussion has centered around hydrocarbon molecules that consist of carbon atoms bonded to each other in long chains. These chains are called normal, straight, or unbranched. The chains may have only single bonds (alkanes), double bonds (alkenes), or triple bonds (alkynes). Hydrocarbons with only single bonds are called saturated hydrocarbons with double or triple bonds are called unsaturated. Not all hydrocarbons want to form straight chains. After all, who among us wants to be straight and serious all the time Some of us will always be comedians. In the world of hydrocarbon molecules, the comedians are the branched and cyclic molecules. 

Spectra of branched saturated hydrocarbons are grossly similar to those of straight-chain compounds, but the smooth curve of decreasing intensities is broken by preferred fragmentation at each branch. The smooth curve for the -alkane in Figure 1.14 (top) is in contrast to the discontinuity at C)2 for the branched alkane (Figure 1.14, bottom). This discontinuity indicates that the longest branch of 5-methylpentadecane has 10 carbon atoms. 

Most oils contain low levels of saturated and unsaturated hydrocarbons. In olive oil, the unsaturated hydrocarbon squalene can constitute up to 40% of the unsaponifiable fraction (Boskou, 1996). Other hydrocarbons commonly present in olive oil are straight chain alkanes and alkenes with 13 to 35 carbon atoms, along with very low amounts of branched chain hydrocarbons. Variations are found between different olive varieties but the main hydrocarbons are those with 23, 25, 27 and 29 carbon atoms (Guinda et al., 1996). Olive oil can clearly be differentiated from other vegetable oils on the basis of hydrocarbon components, and levels of 2.6% crude rapeseed oil or crude sunflower oil can be detected by hydrocarbon analysis (Webster et al., 1999). Terpenes have been identified in the volatile fraction of crude sunflower oil (Bocci and Frega, 1996). 

Acyclic alkanes have the molecular formula C H2 +2 (where = an integer) and contain only linear and branched chains of carbon atoms. They are also called saturated hydrocarbons because they have the maximum number of hydrogen atoms per carbon. 

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