The ketone shown is reduced with sodium borohydride in an achiral solvent, followed by work-up. What is the stereochemical outcome?

AOnly the (S)-enantiomer
BA meso compound
CA racemic mixture, optically inactive
DOnly the (R)-enantiomer

Answer: C

Butanone is prochiral: hydride can attack either face of the planar carbonyl with equal probability in an achiral environment. The alcohol formed (butan-2-ol) has a new stereocentre, and the two enantiomers form in equal amounts, giving a racemic, optically inactive mixture.

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