Oxymercuration of Alkenes to form Ethers using Hg(OAc)2

by James

Description: When an alkene is treated with an alcohol in the presence of mercuric acetate [Hg(OAc)2] it will add to the more substituted position of the alkene (Markovnikoff) to give an ether. The mercury can then be removed using NaBH4.

Notes: The alcohol is generally used as the solvent here.


Notes: Note that in the second reaction, no rearrangement occurs (this would have happened for the acid-catalyzed reaction).

The last example is an intramolecular reaction – often gives students a hard time.

The byproducts in all cases are NaOAc, HOAc, BH3 and Hg(s)

Mechanism: The alkene attacks Hg(OAc)2, displacing acetate and forming a mercuronium ion (Step 1, arrows A and B). Next, the more substituted carbon is attacked by the solvent alcohol (Step 2, arrows C and D). The resulting protonated ether is then deprotonated by acetate (Step 3, arrows E and F). Removal of mercury is done with NaBH4. The mechanism of this step is not generally considered to be “important” for Org 1/ Org 2. However it is shown separately below.

Mechanism for removal of mercury:

Notes: Attack of alcohol (Step 2) occurs trans to the mercury, although that is not depicted here. Removal of mercury proceeds through formation of a free radical, so the reaction is not stereoselective.

{ 3 comments… read them below or add one }

Andrialene Anticuando

okay lang. add more example.



In the last example why wasn’t ROH used along with Hg(OAc)2


Diana Lee

For the removal of mercuric acetate why must sodium borohydride be added in a basic condition?


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