Chair Conformation

In the chair conformation, all the hydrogens are staggered. You can see this by rotating the model to look down the carbon-carbon bonds.

The chair is the lowest energy conformation for cyclohexane.

Boat Conformation

The boat conformation is again a puckered structure that allows tetrahedral bond angles. The boat conformation suffers from torsional strain, making it less stable (higher in energy) than the chair.

Steric strain in the boat arises mainly from the repulsion (steric crowding) between the two hydrogens on the ends of the "boat. These hydrogens, shown in JSmol in magenta, are called flagpole hydrogens, because they point upward from the ends of the boat like two flagpoles. You can see the steric crowding by selecting the spacefilling model from the toolbar. Note that the hydrogens along the "bottom" of the boat are eclipsed, creating additional steric strain in the boat.

The boat conformation is about 29 kJ/mol higher in energy than the chair conformation. Therefore, at any instant most of the molecules in a cyclohexane sample are in chair conformations.

Twisted Boat Conformation

The atoms in the boat conformation can move around considerably to a find a lower energy structure. The conformation that results is called the skewed boat or twisted boat. Note that both the flagpole strain and eclipsing strain have been reduced somewhat. Compare the spacefilled models of the three different conformations.

Even though the twisted boat is lower in energy than the symmetrical boat, it is still about 23 kJ/mol higher in energy than the chair conformation. When someone refers to the "boat conformation," the twisted boat is often intended.