Stereochemistry of Reactions: Addition of Water to an Achiral Alkene


After completing this section, you should be able to account for the stereochemistry of the product of the addition of water to an alkene in terms of the formation of a planar carbocation.

Study Notes

Organic reactions in the laboratory or in living systems can produce chiral centres. Consider reaction of 1-butene with water (acid catalyzed). Markovnikov regiochemistry occurs and the OH adds to the second carbon. However, both R and S products occur giving a racemic (50/50) mixture of 2‑butanol. How does this occur? The proton addition to 1‑butene results in a planar carbocation intermediate. A molecule of water is then equally likely to attack from the top or the bottom of this cation to produce either (S)‑2‑butanol or (R)‑2‑butanol, respectively.mechanism of alkene hydration leading to racemic mixture of two-butanol