25.2. Hydrocarbon Rings http://www.ck12.org
Lesson Summary
- Hydrocarbons can form ringed structures called cyclic hydrocarbons. Cyclopentane and cyclohexane are the
most common cycloalkanes because they have the least ring strain. - Cyclohexane exists in puckered confirmations, such as the chair and boat conformations.
- Benzene is the base structure of aromatic compounds. Benzene has a ring of delocalized electrons, which
provides additional stability to the structure. - Other aromatic compounds can be formed by substituting various groups for one or more of the hydrogen
atoms on benzene. Polysubstituted benzene compounds are named by numbering the carbons in the ring.
Lesson Review Questions
Reviewing Concepts
- Name and give the molecular formula for the simple cycloalkane containing a ring of eight carbon atoms.
- What is the ideal CāCāC bond angle in a cycloalkane? Which two cycloalkanes come closest to the ideal
bond angles? - Which molecule is more reactive: cyclopropane or cyclopentane? Explain.
- Both benzene and cyclohexane are six-membered rings. Why is benzene planar while cyclohexane is not?
- What makes benzene a stable and fairly unreactive molecule?
Problems
- Name the following molecules.
a.b.c.