Skew-boat conformation of cyclohexane

FIGURE 3.12 (a) The boat and (fa) skew boat conformations of cyclohexane. A portion of the torsional strain In the boat Is relieved by rotation about C—C bonds In the skew boat. Bond rotation Is accompanied by movement of flagpole hydrogens away from each other, which reduces the van der Waals strain between them. 

A modified boat conformation of cyclohexane, known as the twist boat (Fig. 1.8), or skew boat, has been suggested to minimize torsional and nonbounded interactions. This particular conformation is estimated to be about 1.5 kcal moE (6 kJ moE ) lower in energy than the boat form at room temperature. 

In the symmetrical boat conformation of cyclohexane, eclipsing of bonds results in torsional strain. In the actual molecule, the boat is skewed to give the twist boat, a conformation with less eclipsing of bonds and less interference between the two flagpole hydrogens. 

The various conformations of cyclohexane are m rapid equilibrium with one another but at any moment almost all of the molecules exist m the chair conformation Not more than one or two molecules per thousand are present m the skew boat confer matron Thus the discussion of cyclohexane conformational analysis that follows focuses exclusively on the chair conformation... 

A potential energy diagram for nng inversion m cyclohexane is shown m Figure 3 18 In the first step the chair conformation is converted to a skew boat which then proceeds to the inverted chair m the second step The skew boat conformation is an inter mediate 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... 

Section 3 7 Three conformations of cyclohexane have approximately tetrahedral angles at carbon the chair the boat and the skew boat The chair is by far the most stable it is free of torsional strain but the boat and skew boat are not When a cyclohexane ring is present m a compound it almost always adopts a chair conformation... 

Skew boat (Section 3.7) An unstable conformation of cyclohexane. It is slightly more stable than the boat conformation. 

Fig. 2-9. Conformations of cyclohexane. 1, Chair 2, boat 3, skew boat 4, half-chair.

FIGURE 3.15 Energy diagram showing interconversion of various conformations of cyclohexane. In order to simplify the diagram, the boat conformation has been omitted. The boat is a transition state for the interconversion of skew boat conformations. 

Three conformations of cyclohexane have approximately tetrahedral angles at carbon the chair, the boat, and the skew boat. The chair is by... 

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