Question

Question: Explain why only one C=C of geraniol is epoxidized with the Sharpless reagent.

Short answer

Answer

The Sharpless epoxidation occurs only for allylic alcohols, and in geraniol, only one C=C is a part of the allylic alcohol functionality.

Step-by-step solution

Sharpless epoxidation

Sharpless epoxidation is the conversion of allylic alcohols to epoxide using the reagents tert-butyl hydroperoxide, (CH₃COOH) a titanium catalyst—usually titanium (IV) isopropoxide, Ti[OCH(CH₃)₂]₄ and diethyl tartrate (DET).

The general reaction scheme is given below:

Sharpless epoxidation using (+)-DET and (-)-DET

Analysis of the given compound

From the structure of geraniol, the allylic alcohol is labeled below:

Allylic alcohol of geraniol

Thus, only one of the C=C groups would take part in the epoxidation reaction since it is a part of the allylic alcohol functionality