The aldehyde shown is racemic. It is treated with methylmagnesium bromide followed by aqueous work-up. How many stereoisomers of the product are formed in total (configurational isomers of the alcohol)?

A1
B4, as two racemic pairs of diastereomers
C2, as two optically active diastereomers
D2, as one racemic pair

Answer: B

2-Phenylpropanal is racemic, and addition creates a second stereocentre, giving 3-phenylbutan-2-ol with two stereocentres. Each aldehyde enantiomer gives two diastereomers, so all four stereoisomers appear: two diastereomers, each as a racemic pair. Enumeration of the product gives 4.

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The aldehyde shown is racemic. It is treated with methylmagnesium bromide followed by aqueous work-up. How many stereoisomers of the product are formed in total (configurational isomers of the alcohol)?

Answer: B

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