Alkanes cyclic, aromatization

Sheppard N and De La Cruz C 1998 Vibrational spectra of hydrocarbons adsorbed on metals. Part II. Adsorbed acyclic alkynes and alkanes, cyclic hydrocarbons including aromatics and surface hydrocarbon groups derived from the decomposition of alkyl halides, etc Adv. Catal. 42 181-313... 

The aromatic hydrocarbons are used mainly as solvents and as feedstock chemicals for chemical processes that produce other valuable chemicals. With regard to cyclical hydrocarbons, the aromatic hydrocarbons are the only compounds discussed. These compounds all have the six-carbon benzene ring as a base, but there are also three-, four-, five-, and seven-carbon rings. These materials will be considered as we examine their occurrence as hazardous materials. After the alkanes, the aromatics are the next most common chemicals shipped and used in commerce. The short-chain olefins (alkenes) such as ethylene and propylene may be shipped in larger quantities because of their use as monomers, but for sheer numbers of different compounds, the aromatics will surpass even the alkanes in number, although not in volume. 

As shown in Table 8, the spray paint solvent is predominately a mixture of several linear aliphatic, branched aliphatic, and cycloaliphatic hydrocarbons, and toluene, xylenes, and ethyl benzene. 2-Butanone (also known as methyl ethyl ketone) was also detected. The breakdown of the solvent mixture by class of compound (aromatic, //-alkane, iso-alkane, cyclic alkane, and others) is shown in Table 9. The solvent appears to be consistent with a mixture of a VM P naphtha... 

With platinum and palladium supported on acidic alumina, cyclopentanes are important intermediates of aromatization (44, 123-124). For example, n-heptane gave about 2-3 times more aromatic product than 2,4-dimethyl-pentane, whereas the formation of C5 cyclic products was about the same from both alkanes. Alkylcyclopentanes aromatized at a reasonable rate (123a). 

When the suffixes a7nea.nd -eneshow up in a compound name like decane or decene they are usually consistent with the alkane and alkene definitions, but not always. Benzene is a cyclic aromatic hydrocarbon, not a straight chain molecule naphthenes are cyclic compounds. 

The GPC of a local crude (Bryan, Texas) sample spiked with a known mixture of n-alkanes and aromatics is shown in Figure 5 and the GPC of the crude is shown in Figure 6. The hydrocarbon mixture is used to calibrate the length of the species which separates as a function of retention volume. Ttie molecular length is expressed as n-alkane carboa units although n-alkanes represent only a fraction of the hydrocarbons in the crude. In addition to n-alkanes, petroleum crude is composed of major classes of hydrocarbons such as branched and cyclic alkanes, branched and cyclic olefins and various aromatics and nonvolatiles namely asphaltenes. Almost all of the known aromatics without side chains elute after n-hexane (Cg). If the aromatics have long side chains, the linear molecular size increases and the retention volume is reduced. Cyclic alkanes have retention volumes similar to those of aromatics. GPC separates crude on the basis of linear molecular size and the species are spread over 10 to 20 ml retention volume range and almost all of the species are smaller than the polystyrene standard (37A). In other words, the crude has very little asphaltenes. The linear... 

The major petroleum resources contain linear, saturated hydrocarbons (alkanes), cyclic alkanes, and aromatics. For the most part, this material is considered to have low free-energy content. 

The exchange of a considerable number of linear, branched-chain, and cyclic alkanes have been studied (5i). The exchange rate increases with increase in the carbon chain length forn-alkanes (methane to hexane). It is found that there is a linear correlation between the logarithm of the exchange rate and the ionization potential of the alkane (Fig. 5 n-alkanes are plotted as circles). This correlation extends to aromatic compounds (Fig. 5 aromatic compounds are plotted as squares) and is evidence that alkanes and aromatic compounds react by a common mechanism. Indeed, the least reactive aromatic, benzene, is only about... 

Part II. Adsorbed Acyclic Alkynes and Alkanes, Cyclic Hydrocarbons Including Aromatics, and Surface Hydrocarbon Groups Derived from the Decomposition of Alkyl Halides, etc. 

Alkanes and Aromatics. The distinction between aromatic and poly-cyclic was arbitrarily set at three conjugated six-member rings in Table I. With this definition the alkanes and aromatic hydrocarbons, with 25 entries, dominate the list of identified components. These compounds are also present in the highest concentration in the different effluents. Ordinarily their concentrations were not measured because of a low interest in these kinds of compounds but in those instances where measurements were made, the amounts ranged from 10-1500 ng/M3 in the vapor phase and from 10-90 ng/g on the suspended particles in the stack effluents. These hydrocarbons were not quantitated for any of the fly and grate ash samples. 

Yunker, M.B., Macdonald, R.W., Cretney, W.J., Fowler, B.R., and McLaughlin, F.A. (1993) Alkane, terpene, and ploy cyclic aromatic hydrocarbon geochemistry of the Mackenzie river and Mackenzie shelf riverine contributions to Beaufort Sea coastal sediment. Geochim. Cosmochim. Acta 57, 3041-3061. 

In this discussion, polar compounds are defined as those that are capable of hydrogen bonding with other polar molecules. Thus, carboxylic acids, phenols, carbazoles, and amides are polar molecules. In addition, molecules such as pyridine benzologs are polar because they can hydrogen bond with carboxylic acids and phenols. Nonpolar molecules are those such as normal alkanes, cyclic alkanes, and aromatic hydrocarbons— molecules that normally do not associate with hydrogenbonding molecules. 

Petrolatum is a purified mixture of semisolid saturated hydrocarbons having the general formula C H2 +2, and is obtained from petroleum. The hydrocarbons consist mainly of branched and unbranched chains although some cyclic alkanes and aromatic molecules with paraffin side chains may also be present. The USP 28 and PhEur 2005 material may contain a suitable stabilizer (antioxidant) that must be stated on the label. The inclusion of a stabilizer is not discussed in the JP 2001 monograph. 

The relative order of increasing adsorptivity of the various sulfur compounds and associated hydrocarbon to be adsorbed on sihca gel, given by Haresnape, Fidler, and Lowry (151), is aromatic hydrocarbons, thiophenes, alkanethiols, alkane disulfides, aromatic and cycloalkanethiols, alkane sulfides, and cyclic sulfides. (The more polar sulfur compounds such as sulfoxides, sulfones, and sulfonic acids would be expected to be more readily adsorbed and therefore would fall at the end of the list.)... 

Unlike most other samples that have to be analysed, petrochemical samples generally contain a limited number of classes of compounds, notably, alkanes, alkenes, cyclic alkanes, and aromatics with a different number of fused rings. The sample dimensionality therefore is rather limited (see below). The absolute number of compounds, however, is not only tremendous, but they all need to be analysed. In other words, the matrix itself is the goal of the analysis. So instead of looking for the needle in the haystack, the haystack itself needs to be characterised. In that respect, it is not too surprising that GCxGC from the conception of the technique on, has been developed using petrochemical samples as a subject [1,2]. 

The word oil is used for an organic phase that is essentially immiscible with water and is thus relatively apolar. It can refer to a hydrocarbon, a partially or totally chlorinated or fluorinated hydrocarbon, single-chain alkane, cyclic or aromatic hydrocarbon, polar monoester such as ethyl oleate, long-chain alcohol such as dodecanol, triglyceride natural oil, or polycyclic cholesterol. The most typical oil phase is, of course, n-alkane, which would be characterized by its length or alkane carbon number (ACN). 

The activity coefficients and interaction parameters w ere also determined for other polymer-solute systems (a) normal, branched and cyclic alkanes and aromatic hydrocarbons in poly (methyl methacrylate) [60,100] ... 

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