Staggered versus eclipsed conformations

One of the most general structural features of saturated hydrocarbons is the preference for staggered versus eclipsed conformations. This preference is seen with the simplest hydrocarbon with a carbon-carbon bond—ethane. The staggered conformation is more stable than the eclipsed by 2.9kcal/mol, as shown in Figure 1.33. ... 

Figure 3.7 A graph of potential energy versus bond rotation in ethane. The staggered conformers are 12 kJ/mol lower in energy than the eclipsed conformers.

FIGURE 2.32 (a) Newman projections for butane. The staggered conformations are shown, (b) A graph of dihedral angle (0) versus energy for hutane as the molecule changes through rotation about the C(2)—C(3) bond. AH three eclipsed conformations are shown. 

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