Section: Chemical and Physical Foundations of Biological Systems

30)
The two molecules above can best be described as:

1. Structural isomers
2. Diastereomers
3. Enantiomers
4. Conformational isomers

The molecule on the left is trans 1, 2-diiodocyclohexane. The molecule on the right is cis 1, 2-diiodocyclohexane. Cis and trans molecules are a type of diastereomer called geometric isomers. A: Structural isomers have fundamentally different connectivity between the atoms. So for example if the iodine were on carbons 1 and 3 and then in the other molecule on carbons 1 and 4, that would be structural isomers. C: Enantiomers are mirror image reflections of each other, which these molecules are not. D: Conformations isomers allow you to freely interconvert between the molecules without breaking any bonds. The classic example is chair and boat cyclohexane. Here, to flip the one iodine from R to S configuration would require breaking a bond in the ring, rotating, and then re-attaching. That requirement for bond-breaking means these are not conformers.