To this point we have focused on alkanes that have free rotation about the carbon-carbon bonds. In this next section, we are going to focus on molecules where this rotation is hindered.
Of the saturated hydrocarbons, the most common reason for hindered rotation is if the chain forms a ring, such as in cyclopropane, cyclobutane, cyclopentane, and cyclohexane. These molecules are not static and the ring structure allows some rotation, but complete rotation is prevented. While partial rotation is possible in all of these rings, we are going to focus on cyclohexanes (6-membered rings) as they are common in nature.
