Cyclohexane

The two carbons at the end of a carbon-carbon single bond are free to rotate about that bond. As this rotation occurs, the steric energy of the molecule changes as the result of torsional strain and van der Waals repulsion between groups attached to the two atoms. In cyclohexane, the bonds are not entirely free to rotate, but partial rotation about carbon-carbon bonds results in different conformations of the cyclohexane ring.

We are now ready to extend our review of basic principles to glucose, which is an oxacyclohexane (one oxygen atom replacing a carbon).