Question

Which of the following combinations can be used for the preparation of cis vic diol?

• A. Alkene, Baeyer reagent
• B. Alkene ,$Os{O}_4$
• C. Alkene, MMPP and $H_{2}O/H$
• D. Both of (A) and (B)

Answer 1

The correct option is B Alkene ,$Os{O}_4$

Osmium tetroxide (OsO4) is a volatile liquid that is most useful for the synthesis of 1,2 diols from alkene.

1. The OsO₄ is a catalyst. It reacts with the π electrons of the alkene in a syn addition to form a cyclic osmate ester.

2. The OH⁻ hydrolyzes the ester. This forms the cis-diol and H₂OsO₄.