Oxymercuration: Alcohols from alkenes using Hg(OAc)2 and Water
Description: Alkenes treated with mercuric acetate [ Hg(OAc)2 ] and water will be hydrated to form alcohols, after addition of NaBH4. The rest of this page is available to MOC Members only.
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Real-Life Example:
Org. Synth. 1973, 53, 94
DOI Link: 10.15227/orgsyn.053.0094
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Doesn’t the mercury atom have an extra electron after step 5 (i.e. isn’t it a free radical)?
Why is this homolytic bond cleavage favored?
The mercury-carbon bond is extremely weak (about 30 kcal/mol versus 100 kcal/mol for a C-H bond). Even mild heat will result in homolytic cleavage.
After cleavage of the C-Hg bond, Hg is in the (I) oxidation state. After the radical abstracts the hydrogen, mercury goes to the Hg (0) oxidation state.
Sorry, but can I know why sometimes THF is used in this reaction? Is it purely a polar solvent which can dissolve the organic compound and Mercuric Acetate? Or it has got to do with the stabilising ability of the oxygen atom on the Hg atom? (Something similiar to why Grignard reactions are performed in ether and THF)
Thanks
Kudos dude. Needed this earlier in the course but sleep is overrated anyway.
it is very helpful for student.thanks to you
Nice. Thanks for the radical mech in reduction step, though should it be Hg(l) instead of Hg(s)?
I point out to my students that the environmental impact of Hg(OAc)2 must be balanced against improved yield and avoidance of C+ rearrangements.
Ha!. Yes, I guess it should be Hg(liquid). The times I’ve done it, it formed this beautiful little grey dispersion, it must have stuck in my mind as a solid & I forgot it’s actually a liquid.