Cis Cyclic Compounds H H C internal mirror plane of symmetry (o) Cis-1,2-dichlorocyclohexane is achiral because the molecule has an internal plane of symmetry.Both structures above can be superimposed. 2013 Pearson Education,Inc. Chapter 5 10© 2013 Pearson Education, Inc. Cis Cyclic Compounds • Cis-1,2-dichlorocyclohexane is achiral because the molecule has an internal plane of symmetry. Both structures above can be superimposed. Chapter 5 10