Figure 3.9 A plot of potential energy versus rotation for the C2-C3 bond in butane. The energy maximum occurs when the two methyl groups eclipse each other, and the energy minimum occurs when the two methyl groups are 180 (องศา) apart (anti).
The notion of assigning definite energy values to specific interactions within a molecule is a very useful one that we’ll return to in the next chapter. A summary of what we’ve seen thus far is given in Table 3.5.
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The same principles just developed for butane apply to pentane, hexane, and all higher alkanes. The most favorable conformation for any alkane has the carbon-carbon bonds in staggered arranged anti to one another. A generalized alkane structure is shown in Figure 3.10.
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