Space-filling models ethane

FIGURE 3 1 The stag gered and eclipsed confer mations of ethane shown as ball and spoke models left) and as space filling models right)... 

Figure 27-3 Models of ethane, C2Hg. (a) The condensed and Lewis formulas for ethane, (b) A ball-and-stick model, (c) a space-filling model of ethane, and (d) a 3-D representation.

The space-filling model of ethane shows two connected tetrahedral arrangements around the two carbon atoms. ... 

Like the hydrocarbon ethane, the space-filling model of ethene has two geometric centers. ... 

The space-filling models of ethane and ethanol are shown below. 

Figure 2.32 (a) Paradoxical hexaaryl ethanes. Calculations at the TPSS/TZV(2d,2p) level of theory with "D3" dispersion corrections find C-C bond scission to be unfavorable In the most sterically crowded case. AC g are for the gas phase calculations. Inclusion of solvation provides -10-12 kcal/mol to the radical products, (b) A space-filling model of the hexaaryl ethane with 12t-Bu groups. (Source Crimme 2011 (52). Reproduced with permission of John Wiley and Sons.)... 

B The Lewis structure of ethane, CjHg. The molecular structure of ethane represented by Q a space-filling model and B a ball-and-stick model. 

Figure 4.1a. (Lefthand side) Ball-and-stick representation of mordenite. (Righthand side) Space filling model of chabazite. Note the difference In size of oxygen and silicon atoms. Ethane is adsorbed in two of the cavities.

From the standpoint of bonding, the important thing to remember is that there are four bonds for each carbon, composed of sp hybrid orbitals. All the bonds are covalent, and there are no rmshared electrons on carbon. The two molecular models of ethane are shown for comparison with the two-dimensional structures, and the electron density potential map is also shown. The ball-and-stick model (5d) shows the relative position of the atoms, and the space-filling model (5e) shows the relative size of the atoms. Note the concentration of electron density between the two carbon atoms and the carbon and hydrogen atoms in 5f, which is consistent with the position of the covalent bonds. 

It should be added, however, that an important factor in these reactions is the overcrowding that takes place when five or six aryl groups are introduced into ethane. It is impossible to construct space-filling models of hexaaryl-ethanes and indeed it now appears that such compounds do not in fact exist. The dimer of triphenylmethyl, which was formerly thought to be hexaphenylethane (Ph C—CPha) in fact has the quinonoid structure (1). Formation of this from triphenylmethyl is much less favorable than formation of Ph3CCPh3 (see the corresponding NBMO coefficients in Fig. 4.5) so far as the n electrons are concerned, but the steric effects outweigh this difference. 

Return to ethane (click on it) and then, one after the other, select Wire, Ball and Wire, Tube, Ball and Spoke, or Space Filling from the Model menu to view ethane with a variety of different models. 

If A and B are large bulky groups they will bump together, attainment of the eclipsed conformation will be almost impossible, and rotation will be severely restricted. Even if A and B are hydrogen atoms (ethane), there will be a rotational barrier in the eclipsed conformation which amounts to 12 kj (3 kcal) per mole because of the crowding of the hydrogen atoms as they pass each other.5 9 This can be appreciated readily by examination of space-filling molecular models. 

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