Space-filling models butane

FIGURE 3 8 Ball and spoke and space filling models of methyl-methyl eclipsed conformation of butane... 

Examine space-filling models for the two conformers and identify any likely unfavorable nonbonded interactions. Based on steric effects, which conformer would you anticipate would be the more stable Compare energies of anti-1,2-ethanediol and gauche-1,2-ethanediol to see if you are correct. Is this the same ordering of conformer energies as seen for n-butane (see Chapter 5, Problem 3)7... 

Butane and 2-methylpropane, whose space-filling models are shown at the top of the next column, are both nonpolar and have the same molecular formula, C4H10, yet butane has the higher boiling point (—0.5 °C compared to — 11.7 °C). Explain. 

Figure 1.12 Space-filling models of the isomeric butanes.

The methyl-methyl eclipsed conformation of butane (a) ball-and-spoke model, (b) space-filling model, and (c) electrostatic potential map. The molecule itself is the same size in each. 

Note that structural formulas are generally not three-dimensional representations of the molecule— as space-filling or ball-and-stick models are— bnt rather two-dimensional representations that show how atoms are bonded together. As snch, the most important feature of a structural formula is the connectivity of the atoms, not the exact way the formula is drawn. For example, consider the two condensed structural formulas for butane and the corresponding space-filling models below them ... 

Figure 1 A computational chemistry lecture in the main auditorium of the Department of Chemistry of the University of Geneva, with the videodata projector (top right) displaying on the screen a space-filling model of the butane molecule generated on a PC by HYPERCHEM...

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