Question

which of these will result in a racemic mixture?
rxn i
rxn ii
a. rxn i only
b. rxn ii only
c. both result in racemic mixtures
d. neither result in a racemic mixture

Explanation:

• For Rxn I: The hydrogenation of the alkene (using \(H_2/Pt\)) forms a new chiral center. Since the addition of \(H_2\) to the double - bond (in the absence of a chiral catalyst) is a syn - addition but can occur from either face of the double - bond with equal probability, a racemic mixture is formed.
• For Rxn II: The starting alkene is symmetric (\(CH_3CH = C(CH_2CH_3)_2\)). After hydrogenation (\(H_2/Pt\)), the product \(CH_3CH_2CH(CH_2CH_3)_2\) has no chiral centers. A racemic mixture is a 1:1 mixture of enantiomers, and since there are no chiral centers in the product of Rxn II, it cannot form a racemic mixture.

Answer:

A. Rxn I only