What stereoisomers are obtained from hydroboration–oxidation of cis -2-butene?

Feb 2, 2015

The product is a racemic mixture of ($R$)-butan-2-ol and ($S$)-butan-2-ol.

If the BH₃ attacks from the top of the alkene

we get the borane

The product on oxidation with H₂O₂ is ($S$)-butan-2-ol.

If the BH₃ attacks from the bottom of the alkene

we get the borane

The product on oxidation with H₂O₂ is ($R$)-butan-2-ol.

There is an equal chance of attack from top or bottom, so we get a 50:50 mixture of the two stereoisomers.