An isopropyl group is larger than a methyl group, so the isopropyl group has greater torsional strain when axial, and a stronger driving force to be equatorial. While both equilibria shown above lie to the right, the K eq for isopropylcyclohexane is greater than K eq for methylcyclohexane. A stereoisomer that is not an enantiomer. A compound that is achiral but contains a stereocenter. Draw the structure of a racemic mixture.
Enantiomers are nonsuperimposable mirror images.
Biochemical effect arise when molecules interact with biomolecules such as enyzmes. These biomolecules are constructed of chiral building blocks such as amino acids. Thus, an enzyme may fit one enatiomer of a molecule better than the other enantiomer. In the case of the thalidomide enantiomers, the S enantiomer fits into a receptor that triggers a teratogenic response. The R enantiomer fits into a different receptor, triggering a hypnotic or sedative response.