Alkane series

Under standard conditions of temperature and pressure (STP), the first four members of the alkane series (methane, ethane, propane, and butane) are gases. As length of the carbon increases the density of the compound increases (pentane) to C yHgg are liquids, and from C.,gH3g, the compounds exist as wax-like solids at STP. 

The most common prefixes are written below using the alkane series as an example, and the prefixes are highlighted ... 

It is seen that by taking a mean value for the slope, there is very little divergence between the calculated and experimental values. Consequently, the methylene groups can, indeed, be taken as a reference group for assessing the effect of molecular structure on solute retention. The concept will now be applied to a simple n-alkanes series as discussed above, the data for which was obtained on the stationary phase n-heptadecane. 

Note that there is no one-carbon alkene corresponding to methane, since hydrogen can never form more than one covalent bond, and there is no other carbon atom in the structural formula. Therefore, the first compound in the alkene series is ethene, while the corresponding two-carbon compound in the alkane series, ethane, is the second compound in the series, with methane the first. 

Propane (C.Hg) is one of the saturated open-chain hydrocarbons that form the paraffin or alkane series... 

At ambient temperature and pressure, the first four members of the n-alkane series (methane to n-butane) are gases, the next thirteen (n-pentane through n-heptadecane) are liquids, and the higher members from n = 18 on are solids. 

Alkenes also form a homologous series as the carbon number increases, the number of possible isomeric structures for each member increases more rapidly than in the case of the alkane series. 

Methane is the first memher of the alkane series and is the main component of natural gas. It is also a hy-product in all gas streams from processing crude oils. It is a colorless, odorless gas that is lighter than air. Table 2-1 shows selected physical properties of C1-C4 paraffinic hydro-carhon gases. 

Propane, the next higher member in the alkane series., also has a torsional barrier that results in hindered rotation around the carbon-carbon bonds. The barrier is slightly higher in propane than in ethane—a total of 14 kj/mol (3.4 kcal/mol) versus 12 kj/mol. 

The effect of different backbones on ero.sion rates was demonstrated in a study of the homologous poly[ (p-carboxyphenoxy)alkane] series. As the number of methylene groups in the backbone increased from 1 to 6, thus decreasing the reactivity of the anhydride linkage and rendering the polymer more hydrophobic, the erosion rates underwent a decrease of three orders of magnitude (4). 

Oils The n-alkane series Cg-C, toluene and cyclohexane were purchased from BDH, Poole, UK, each with a stated purity of 99% reagents were used as received. Crude oil samples were obtained from two North Sea fields one located in the Norwegian sector and the other from the UK sector. Stock tank oil from the Gullfaks field was supplied by Statoil, Norway and the other stock tank oil from an undisclosed source. Both crude oils are derived from sandstone formations with reservoir temperatures of 70° and 101°C respectively. 

Ehase Inversion Temperatures It was possible to determine the Phase Inversion Temperature (PIT) for the system under study by reference to the conductivity/temperature profile obtained (Figure 2). Rapid declines were indicative of phase preference changes and mid-points were conveniently identified as the inversion point. The alkane series tended to yield PIT values within several degrees of each other but the estimation of the PIT for toluene occasionally proved difficult. Mole fraction mixing rules were employed to assist in the prediction of such PIT values. Toluene/decane blends were evaluated routinely for convenience, as shown in Figure 3. The construction of PIT/EACN profiles has yielded linear relationships, as did the mole fraction oil blends (Figures 4 and 5). The compilation and assessment of all experimental data enabled the significant parameters, attributable to such surfactant formulations, to be tabulated as in Table II. 

Compounds consisting of only carbon and hydrogen have the simplest compositions of all organic compounds. These compounds are called hydrocarbons. It is possible to classify the hydrocarbons into four series, based on the characteristic structures of the molecules in each series. These series are known as (1) the alkane series, (2) the alkene series, (3) the alkyne series, and (4) the aromatic series. There are many subdivisions of each series, and it is also possible to have molecules that could be classified as belonging to more than one series. 

The alkane series is also called the saturated hydrocarbon series because the molecules of this class have carbon atoms connected by single bonds only, and therefore have the maximum number of hydrogen atoms possible for the number of carbon atoms. These substances may be represented by the general formula C H2,I + 2 and molecules of successive members of the series differ from each other by only a CH2 unit. The line formulas and names of the first 10 members of the series, given in Table 21-2, should be memorized because these names form the basis for naming many other organic compounds. It should be noted that the first parts of the names of the later members listed are the... 

Waggott [57] reported that a factor of major concern in adapting the technique to more polluted samples is the capacity of the carbon filter, which usually contains only 1.5-2 mg carbon. He showed that the absolute capacity of such a filter for a homologous series of 1-chloro-n-alkanes was 6 xg for complete recovery. Maximum recovery was dependent on carbon number, being at a maximum between Cs and C12 for the 1-chloro-n-alkane series. It is important, therefore, to balance the amount of sample stripped with the capacity of the carbon filter to obtain better than 90% recoveries. 

The alkane series is present in mass spectra of any compound containing an alkyl group. In case of isobaric series (e.g., alkanes and ketones) one should pay attention to the intensities of the isotopic peaks. Thus, for the isobaric ions of m/z 43 (CH3CO and C3H7) the abundance of the isotopic peak (m/z 44 ion) will be 2.2% and 3.3%, respectively. The situation is very simple with A + 2 elements. In this case there are two homologous ion series due to A and A + 2 ions. It is worth emphasizing that... 

The correct analysis of the homologous ion series has certain limitations. Low abundances of peaks in some series require the attention and experience of a researcher. Usually alkane series are dominated in the mass spectra of the most various compounds. Fragmentation initiated by one functional group may completely suppress or notably camouflage other reactions of polyfunctional substances. In the latter case it is useful to consider IR-spectroscopy data in mass spectral interpretation. 

The saturated open-chain hydrocarbons form a homologous series called the paraffin series or the alkane series. The composition of each of the members of the series corresponds to the formula CnH2n + 2> where n is the number of carbon atoms in the molecule. All the members of the series are unreactive. They do not react readily at ordinary temperatures with such reagents as acids, alkalies, or oxidizers. 

Methane, also referred to as marsh gas, is a gas composed of carbon and hydrogen with a chemical formula of CH4. It is the first member of the paraffin or alkane series of hydrocarbons. It is lighter than air, colorless, odorless, tasteless and is flammable. It occurs in natural gas and as a by-product of petroleum refining. In atmospheric burning no smoke production normally occurs. In air methane bums with a pale, faintly luminous flame. With excess air carbon dioxide and water vapor is formed during combustion, with an air deficiency carbon monoxide and water is formed. It forms an explosive mixture with air over a moderate range. Its primary uses are as a fuel and raw feedstock for petrochemical products. 

Homologous long chain -alkane series ranging from C38 with no carbon number predominance [ 1,53 - 55,73,109 -114]... 

The branched f -alkane series are biomarkers because of the locale of their occurrence and the presence of only alternate pseudohomologs (even- or odd-carbon numbers only). Their inferred origin is from probable microbial precursors of unknown species, where methylation and ethylation, diethylation, butylation and ethylation occurred during biosynthesis... 

Continuing in the alkane series (also called the paraffin series because the first solid hydrocarbon in the series is paraffin, or candle wax), the next compound is pentane. This name is derived from the Greek word penta, for five. As its name implies, it has five carbon atoms, and its molecular formula is C,H12. From pentane on, the Greek prefix for the numbers five, six, seven, eight, nine, ten, and so on are used to name the alkanes, the Greek prefix corresponding to the number of carbon atoms in the molecule. The first four members of the alkane series do not use the Greek... 

The spectra of normal alkanes (paraffins) can be interpreted in terms of four vibrations, namely, the stretching and bending of C—H and C—C bonds. Detailed analysis of the spectra of the lower members of the alkane series has made detailed assignments of the spectral positions of specific vibrational modes possible. 

The band resulting from the methylene rocking vibration (p CH2), in which all of the methylene groups rock in phase, appears near 720 cm-1 for straight-chain alkanes of seven or more carbon atoms. This band may appear as a doublet in the spectra of solid samples. In the lower members of the w-alkane series, the band appears at somewhat higher frequencies. 

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