Energy diagram for ring inversion of cyclohexane

For typical substituted cyclohexanes, the slow-exchange condition is met at temperatures below about -50°C. Table 3.4 presents data for the half-life for conversion of the equatorial conformation of cyclohexyl chloride to the axial conformation as a function of temperature. 

From these data, it can be seen that conformationally pure solutions of 

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Fig. 3.4. Energy diagram for ring inversion of cyclohexane. [For a rigorous analysis of ring inversion in cyclohexane, see H. M. Pickett and H. L. Strauss, J Am. Chem. Soc. 92 7281 (1979).]...

A potential energy diagram for ring inversion in cyclohexane is shown in Figure 3.18. In the first step the chair conformation is converted to a skew boat, which then proceeds to the inverted chair in the second step. The skew boat conformation is an intermediate in the process of ring inversion. Unlike a transition state, an intermediate is not a potential energy maximum but is a local minimum on the potential energy profile. 

Energy diagram for ring inversion in cyclohexane. The energy of activation is the difference in energy between the chair and half-chair conformations. The skew boat conformations are intermediates. The boat and half-chair conformations are transition states. 

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