Hydrocarbon molecules aromatics

Aqueous mineral acids react with BF to yield the hydrates of BF or the hydroxyfluoroboric acids, fluoroboric acid, or boric acid. Solution in aqueous alkali gives the soluble salts of the hydroxyfluoroboric acids, fluoroboric acids, or boric acid. Boron trifluoride, slightly soluble in many organic solvents including saturated hydrocarbons (qv), halogenated hydrocarbons, and aromatic compounds, easily polymerizes unsaturated compounds such as butylenes (qv), styrene (qv), or vinyl esters, as well as easily cleaved cycHc molecules such as tetrahydrofuran (see Furan derivatives). Other molecules containing electron-donating atoms such as O, S, N, P, etc, eg, alcohols, acids, amines, phosphines, and ethers, may dissolve BF to produce soluble adducts. 

For aromatic hydrocarbon molecules, in particular, the main acceptor modes are strongly anharmonic C-H vibrations which pick up the main part of the electronic energy in ST conversion. Inactive modes are stretching and bending vibrations of the carbon skeleton. The value of Pf provided by these intramolecular vibrations is so large that they act practically as a continuous bath even without intermolecular vibrations. This is confirmed by the similarity of RLT rates for isolated molecules and the same molecules imbedded in crystals. 

In this model there is a quantitative difference between RLT and electron transfer stemming from the aforementioned difference in phonon spectra. RLT is the weak-coupling case S < 1, while for electron transfer in polar media the strong-coupling limit is reached, when S > 1. In particular, in the above example of ST conversion in aromatic hydrocarbon molecules S = 0.5-1.0. 

Fig. 12. A, Schematic representation of parallel arrays of polynuclear aromatic hydrocarbon molecules in a mesophase sphere. B, a) isolated mesophasc spheres in an isotropic fluid pitch matrix b) coalescence of mesophase c) structure of semi-coke after phase inversion and solidification.

Molecular sieves are available with a variety of pore sizes. A molecular sieve should be selected with a pore size that will admit H2S and water while preventing heavy hydrocarbons and aromatic compound.s from entering the pores. However, carbon dioxide molecules are about the same size as H2S molecules and present problems. Even thougli die COi is non-polar and will not bond to the active sites, the CO2 will entci the pores. Small quantities of CO2 will become trapped in the pores In this way small portions of CO2 are removed. More importantly, CO ih obstruct the access of H2S and water to active sites and decrease the eflectiveness ot the pores. Beds must be sized to remove all water and to pi ovitte for interference from other molecules in order to remove all H i.S. 

Recently, Weissman and his colleagues52 showed that the product is paramagnetic indicating that it results from an electron transfer process giving one unpaired electron to the hydrocarbon ion. Furthermore, they demonstrated30 that electron transfer reactions easily proceed in systems containing aromatic" ions and neutral aromatic hydrocarbon molecules, e.g., naphthalene" + phenathrene - naphthalene -j- phenanthrene". 

The effective cross-section of an /z-alkane molecule is smaller than 5 A the effective cross-section of branched, cyclic, or aromatic hydrocarbon molecules is larger than 5 A. Therefore only n-alkanes are adsorbed by a 5-A zeolite all other types of hydrocarbons are excluded. The adsorbed n-alkanes can be recovered by different methods and are subsequently available in a pure form, for further processing. 

Values of the diamagnetic anisotropy of benzene and other aromatic hydrocarbon molecules are calculated on the basis of the assumption that the p, electrons (one per aromatic carbon atom) are free to move from carbon atom to adjacent carbon atom under the influence of the impressed fields. When combined with the assumed values for the contributions of the other electrons (-2.0X 10-6 for hydrogen, —4.5 X10 c for aromatic carbon, — 6.0XlO-6 for aliphatic carbon) these lead to principal diamagnetic susceptibilities of molecules in approximate agreement with the available experimental data. The diamagnetic anisotropy of graphite is also discussed. 

In Table II there are given the available experimental values of the principal susceptibilities of aromatic hydrocarbon molecules, from the papers of Krishnan and his collaborators.111 lc 10 It should be mentioned that in some cases the values have been obtained from crystal susceptibilities in a straightforward manner, with... 

In this way, the conjunct polymers serve as a reservoir of hydride ions. Under some conditions, the polymers are a source of hydride ions, but they accept these ions under other conditions. Substantial amounts of the saturated products are supposedly formed via this route with sulfuric acid. In zeolites, species similar to conjunct polymers also form. The heavy hydrocarbon molecules, which deactivate the catalyst by pore blocking or by site blocking, are generally termed soft coke or low-temperature coke , because of the absence of aromatic species. 

Peover, M. E. Oxidation and Reduction of Aromatic Hydrocarbon Molecules at Electrodes, in Reactions of Molecules at Electrodes, Hush, N. S., Ed., Wiley New York, 1971, pp. 259-281. 

A petrochemical is any chemical (as distinct from fuels and petroleum products) manufactured from petroleum (and natural gas) and used for a variety of commercial purposes (Table 3.8). The definition, however, has been broadened to include the entire range of aliphatic, aromatic, and naphthenic organic chemicals, as well as carbon black and inorganic materials such as sulfur and anunonia. Petroleum and natural gas are made up of hydrocarbon molecules, which comprise one or more carbon atoms to which hydrogen atoms are attached. Currently,... 

Catalytic reforming rearranging hydrocarbon molecules in a gasoline-boiling-range feedstock to produce other hydrocarbons having a higher antiknock quality isomerization of paraffins, cyclization of paraffins to naphthenes (g.v.), dehy-drocyclization of paraffins to aromatics (g.v.). 

Pople, J. A. The electronic spectra of aromatic molecules. II A theoretical treatment of excited states of alternant hydrocarbon molecules based on self-consistent molecular orbitals. Proc. Phys. Soc. (London) A 68, 81—89 (1955). 

When type X is utQized, in any of its ion exchange forms, for dehydration or possibly for sweetening (sulfur removal), there is little likelihood that the intracrystalline diffusion will be the dominant resistance to mass transfer. Large aromatic sulfurs would of course be an exception. When type X is used for adsorption of hydrocarbons or aromatics then it is possible that the micro-pore diffusion might dominate. When type A is used there is always a distinct possibility that intra-crystalline diffusion will be slow and may dominate the mass transfer, even for relatively small molecules. This is especially true when the chosen structure is a K A or type 3A. Selection of other small pore structures, for separations or purification applications can also create situations where the dominant resistance is found in the crystaUites. 

Over the years, many people contributed to the development of the field of organic chemistry. To better understand how this science provides so many useful items for our daily use, it is necessary to be familiar with some of the nomenclature of organic chemistry. There are two basic types of hydrocarbon substances, namely, aliphatic and aromatic. There are three basic types of aliphatic hydrocarbon molecules defined by the number of bonds involved in straight linear-chained molecules. If the basic structure of a hydrocarbon molecule is a ring instead of a straight chain, they are known as aromatic hydrocarbons, typified by the benzene ring. 

The length of a hydrocarbon molecule also has a depression effect on water solubility. Figure 6.8 shows the series of paraffins, 1-olefins, cycloparaffins, aromatics, and acetylenes. The longer hydrocarbon molecules with more —CH2— groups have much lower water solubility, so that each additional —CH2— group drops the water solubility by a factor of almost five. 

Aromatic and Aralkyl Hydrocarbons An aromatic ring in a molecule stabilizes the molecular ion peak (rule 4, Section 2.7), which is usually sufficiently large that accurate intensity measurements can be made on the M + 1 and M + 2 peaks. 

Improved methods of chemical treatment and solvent extraction of petroleum oils remove aromatic hydrocarbon molecules which oxidize readily to form sludge and which have high temperature coefficients of viscosity (low viscosity index). Such treatments have a secondary beneficial effect because oils so treated are more susceptible to further improvement by antioxidants and detergents. 

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