Organic Chemistry: Stereochemistry Flashcards

Optical purity (enantiomeric excess) of a sample showing 50% of maximum rotation is:

Answer: 50%

Enantiomeric excess equals the observed rotation divided by the pure enantiomer's rotation, here 50%.

Resolution of a racemic mixture is commonly achieved by:

Answer: Reaction with a chiral resolving agent to form diastereomers

Converting enantiomers to diastereomers with a chiral agent allows separation by physical properties.

A molecule is chiral if it:

Answer: Is non-superimposable on its mirror image

Chirality means the molecule cannot be superimposed on its mirror image.

Tartaric acid's meso form differs from its (R,R) and (S,S) forms because the meso form is:

Answer: Optically inactive due to internal symmetry

Meso tartaric acid has an internal mirror plane, making it optically inactive unlike the chiral forms.

Which is true about the number of stereoisomers when a meso compound exists for 2 stereocenters?

Answer: There are fewer than 2^n due to the meso form

A meso compound reduces the count below 2^n because two would-be isomers are identical.

Newman projection: the staggered conformation is favored because it:

Answer: Minimizes torsional strain

The staggered arrangement places bonds 60° apart, minimizing torsional (eclipsing) strain.

If a chiral drug's enantiomers have different biological activity, this is because:

Answer: Biological receptors are themselves chiral

Chiral receptors distinguish enantiomers, so each can produce different biological effects.