Ethane representations

To illustrate calculations for a binary system containing a supercritical, condensable component. Figure 12 shows isobaric equilibria for ethane-n-heptane. Using the virial equation for vapor-phase fugacity coefficients, and the UNIQUAC equation for liquid-phase activity coefficients, calculated results give an excellent representation of the data of Kay (1938). In this case,the total pressure is not large and therefore, the mixture is at all times remote from critical conditions. For this binary system, the particular method of calculation used here would not be successful at appreciably higher pressures. 

Figure 2-17. a) The redundanl bond malrix of ethanal with ihe zero values omitted, b) It can be compressed by reduction to the top right triangle, c) Omitting the hydrogen atoms provides the simplest non-redundant matrix representation. 

FIGURE 8.2 Cartesian coordinate representation of ethane. The first column is the element, the other columns are the x, y, and z Cartesian coordinates. 

Acyclic Compounds. Different conformations of acyclic compounds are best viewed by construction of ball-and-stick molecules or by use of Newman projections (see Fig. 1.2). Both types of representations are shown for ethane. Atoms or groups that are attached at opposite ends of a single bond should be viewed along the bond axis. If two atoms or groups attached at opposite ends of the bond appear one directly behind the other, these atoms or groups are described as eclipsed. That portion of the molecule is described as being in the eclipsed conformation. If not eclipsed, the atoms... 

The formalism that we have set up to describe chain flexibility readily lends itself to the problem of hindered rotation. Figure 1.8a shows a sawhorse representation of an ethane molecule in which the angle of rotation around the bond is designated by electron repulsion between the atoms bonded to... 

For a carbon-carbon bond located along a polymer backbone, the preceding molecular representation must be modified to Fig. 1.8c. The chain segments on either side of the bond of interest are substituents for which the amount of steric hindrance follows a slightly different pattern than for the unsubstituted ethane. Using the same convention for [Pg.58]

Convert the following representation of ethane, C2H6/ into a conventional drawing that uses solid, wedged, and dashed lines to indicate tetrahedral geometry around each carbon (gray = C, ivory = H). 

Figure 3.6 A sawhorse representation and a Newman projection of ethane. The sawhorse representation views the molecule from an oblique angle, while the Newman projection views the molecule end-on. Note that the molecular model of the Newman projection appears at first to have six atoms attached to a single carbon. Actually, the front carbon, with three attached green atoms, is directly in front of the rear carbon, with three attached red atoms.

Ethylene is a simple compound of carbon and hydrogen with the formula QH4. Thus it has two less hydrogen atoms than does ethane, QH6. This means that to write a structure of ethylene we must take account of two electrons that are not used in C—H bond formation. Suppose we write an electron dot representation involving only single bonds... 

A graphical representation of diamantane solubility data [36] in various supercritical solvents (carbon dioxide and ethane at 333 K and methane at 353 K) is shown in Fig. 12. 

Figure 9.6. Schematic representation of the catalytic cycle for the hydrodesulfurization of a sulfur-containing hydrocarbon (ethane thiol) by a sulfur vacancy on M0S2 The C2H5SH molecule adsorbs with its sulfur atom towards...

The wealth of information accessible by analyzing this type of PFG NMR data is reflected in Figure 3.1.1. This shows a representation of the (smoothed) propagators for ethane in zeolites NaCaA (a special type of nanoporous crystallite) at two different temperatures and for two different crystal sizes. Owing to their symmetry in space, it is sufficient to reproduce only one half of the propagators. In fact,... 

The above quasi three-dimensional representations are known as sawhorse and Newman projections, respectively. The eclipsed and staggered forms, and the infinite variety of possible structures lying between them as extremes, are known as conformations of the ethane molecule conformations being defined as different arrangements of the same group of atoms that can be converted into one another without the breaking of any bonds. 

Figure 11.18 Two conformational isomers of ethane, C2H6. (a) Sawhorse representation and (b) Newman projections.

A simpler model for ethane recognizes what we already know for methane that each carbon atom is bonded to four other atoms. Given that knowledge, we can now write simply, CH3—CH3, showing only the carbon-carbon bond. Since each carbon atom forms four bonds and since only one is shown (the carbon-carbon bond), it follows that each carbon atom must make three bonds to hydrogen atoms. Even simpler is the model CH3CH3, in which none of the chemical bonds is shown directly. Once we have gained more experience, it will be clear that this simple representation contains all the information that the more detailed one does. Here are two other models for ethane ... 

Note how we have resorted to another form of representation of the ethane, ethylene, and acetylene molecules here, representations that are probably familiar to you (see Section 1.1). These line drawings are simpler, much easier to draw, and clearly show how the atoms are bonded - we use a line to indicate the bonding molecular orbital. They do not show the difference between a and rr bonds, however. We also introduce here the way in which we can represent the tetrahedral array of bonds around carbon in a two-dimensional drawing. This is to use wedges and dots for bonds instead of lines. By convention, the wedge means the bond is coming towards you, out of the plane of the paper. The dotted bond means it is going away from you, behind the plane of the paper. We shall discuss stereochemical representations in more detail later (see Section 3.1). 

Let us consider first the simple alkane ethane. Since both carbons have a tetrahedral array of bonds, ethane may be drawn in the form of a wedge-dot representation. 

The two representations shown here are actually two different conformers of ethane there will be an infinite number of such conformers, depending upon the amount of rotation about the C-C bond. Although there is fairly free rotation about this bond, there does exist a small energy barrier to rotation of about 12kJmol due to repulsion of the electrons in the C-H bonds. By inspecting the Newman projections, it can be predicted that this repulsion will be a minimum when the C-H bonds are positioned as far away from each other... 

Let us now consider rotation about the central C-C bond in butane. Rotation about either of the two other C-C bonds will generate similar results as with ethane above. Wedge-dot, Newman, and sawhorse representations are all shown use the version that appears most logical to you. 

The structure of the molecule is the most important information in the prediction of properties. One method of representation is to specify the (x, y, z) coordinates of all the atomic nuclei. Another method, which is more compact and useful, is to list the positions of the atoms by the internal coordinate method called the Z matrix. For instance, this is given for ethane in table 4.6. 

Figure 6.9. Top to bottom Two possible Jahn-Teller distorted geometries for the methane radical cation and calculated geometry for its energy minimum schematic representation of the SOMO for ethane radical cation SOMOs of three different propane radical cations observed by ESR the SOMO of butane radical cation and SOMOs for two conformers of pentane radical cation.

The adsorbed species discussed above are simplified representations of the actual surface complexes since the number of participating surface metal atoms and the number of bonds between the molecule and the surface are not known. Hydrogenolysis reactions, however, are believed to take place on multiple surface sites, specifically, on a certain ensemble of atoms. For example, on the basis of kinetic data, Martin concluded273 that at least 12 neighboring nickel atoms free from adsorbed hydrogen are required in the complete cleavage of ethane ... 

Ellipsoid of inertia, 198-202,439-440 Emission of radiation spontaneous, 121-122 stimulated, 118, 120,122,135-139 Energy conversion factors, 468 Energy-localized orbitals, 69, 103-104 Equilibrium frequencies, 147, 262 Equivalent representations, 400 Ethane ... 

The substitution system of nomenclature should be viewed as showing only how atoms are connected and not as indicating the precise electronic structure. Thus -adsorbed ethylene is one representation of 1,2-diadsorbed ethane. 

Natural gas is usually produced from the well and transported to the gas processing plant at high pressure, in the range 500-1500 psi. To minimize recompression costs, the membrane process must remove impurities from the gas into the permeate stream, leaving the methane, ethane, and other hydrocarbons in the high-pressure residue gas. This requirement determines the type of membranes that can be used for this separation. Figure 8.30 is a graphical representation of the factors of molecular size and condensability that affect selection of membranes for natural gas separations. 

Ethane C2H8 — 2CH3. The models for the ethane molecule, C—C rupture complex, and H rupture complex are the molecule, complex 3, and complex 4, respectively, shown in Table I. For illustrative purposes and consistency with Sec. II, the 350 torsion model of ethane, rather than the internal rotation model, was used. The latter would be a better conceptual representation, but, in fact, for the relevant energies, to = 85 kcal. mole, there is little practical difference (cf. Sec. II-C,3). The calculated results which are obtained by combining the kt values, Figure 2, with the distribution function that is appropriate for the activation technique, Figure 8, are shown in Table XII. 

These representations of the hydrocarbon ethane, C2H6, were made using different modelling kits. Your school may have one or more of these kits available. 

Notice that in this table we retained the Longuet-Higgins notation for the irreducible representations An in accordance to that of ethane [4]. 

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