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Chemistry LibreTexts

8.8: Stereochemistry of Reactions - Hydration of Chiral Alkenes

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  • Learning Objective

    • discern the stereochemical differences between the EAR of chiral and achiral alkenes

    Stereochemistry - the Subtle Details

    In the previous section, the addition of water to the achiral alkene produced a racemic mixture of two enantiomeric alcohols. They are produced in equal amounts so the mixture is optically inactive. What would occur if we carried out a similar reaction on a chiral alkene? Consider (S)-3-methyl-1-pentene reacting with water (acid catalyzed). Proton addition produces a carbocation intermediate that is chiral (* denotes stereogenic centre). That intermediate does not have a plane of symmetry and therefore attack by water is not equal from the top and bottom. This ultimately produces R and S products in a non 50:50 ratio as shown in the mechanism below.

    alkene chiral hydration.png


    1. Predict the products of the following reaction showing stereochemistry.


    1. The products are diastereomers of one another.