Chapter 15: Alcohols, Diols and Thiols

Alkoxymercuration-Demercuration of Alkenes
(review of Chapter 14)

Summary

• Overal transformation C=C to H-C-C-OR
• Typical reagents are mercury acetate, Hg(OAc)₂ in ROH / THF
• Unfortunatley, mercury compounds are generally quite toxic
• Regioselectivity predicted by Markovnikov's rule
• The reaction is not stereoselective
• Reaction proceeds via the formation of a cyclic mercurinium ion

• The mercurinium ion is opened by the attack of alcohol to complete the alkoxymercuration.
• When the alcohol attacks, it does so at the more highly substituted carbon.
• Demercuration is effected by a reduction using sodium borohydride, NaBH₄

QUESTIONS
Are rearrangements a problem with this process ? ANSWER
Why does the alcohol attack the more highly substituted carbon ? ANSWER

• Oxymercuration-demercuration of alkenes (Ch 14)

© Dr. Ian Hunt, Department of Chemistry