the molecule is said to be totally eclipsed and is in its highest-energy state. Totally eclipsed
conformations are the least favorable energetically because the two largest groups are
synperiplanar (in the same plane, on the same side). The different staggered and eclipsed
conformations are demonstrated in Figures 2.3 and 2.4. For compounds larger than butane, the
name of the conformation is decided by the relative positions of the two largest substituents about
a given carbon–carbon bond.
Figure 2.4. Stability of Straight-Chain Conformational Isomers
Degree measurements indicate the angle between the two largest substituents about the carbon–
carbon bond.Figure 2.5 shows the plot of potential energy vs. degree of rotation about the bond between C-2 and
C-3 in butane. It shows the relative minima and maxima of potential energy of the molecule
throughout its various conformations. Remember that every molecule wants to be in the lowest
energy state possible, so the higher the energy, the less time the molecule will spend in that
energetically unfavorable state.