Q. 8-8-71E - Organic Chemistry (Mcmurry)

Question

Hydroxylation of cis-2-butene with ${\mathbf{OsO}}_{\mathbf{4}}$yields a different product than hydroxylation of trans-2-butene. Draw the structure, show the stereochemistry of each product, and explain the difference between them.

Step-by-Step Solution

Answer

Hydroxylation of cis-2-butene with OsO 4

Hydroxylation of an alkene with osmium tetroxide happens with syn stereochemistry. Cis reactant leads to the formation of cis product. The reaction occurs by forming a cyclic osmate intermediate in a single step reaction with an alkene, which on oxidation leads to 1,2 diol.

Oxidation of osmate does not affect the stereochemistry of the carbon-oxygen bond.

Hydroxylation of Trans-2-butene with OsO 4

Hydroxylation of an alkene with osmium tetroxide happens with syn stereochemistry. Cis reactant leads to the formation of cis product. The reaction occurs with the formation of a cyclic osmate intermediate in a single step reaction with an alkene, which on oxidation leads to the formation of 1,2 diol.

Oxidation of osmate does not affect the stereochemistry of the carbon-oxygen bond.