Organic Chemistry Online Notes: Ether syntheses (cont.)
Alkoxymercuration-demercuration
In this reaction, a molecule of alcohol is added across the double bond of an alkene to produce an ether. Mercuric Acetate (CH3COOHgOOCCH3, abbreviated Hg(OAc)2) dissociates forming a +HgOAc ion, which bonds with the alkene to form a mercurinium cation with a three-membered ring (two carbons and the mercury atom, each one bonded to the other two). The alcohol (HO-R) then attacks this mercurinium ion at the more highly substituted of the two carbons that formerly made up the double bond. The addition of the alkoxy group, therefore, follows the Markovnikov rule. The HgOAc group remains bonded to the less substituted carbon. It is then removed (hence the "demercuration") by the reducing agent NaBH4, sodium borohydride, which replaces it with a hydrogen.
C=C + Hg(OAc)2 ==ROH==> RO-C-C-HgOAc ==NaBH4==> RO-C-C-H
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In this reaction, a molecule of alcohol is added across the double bond of an alkene to produce an ether. Mercuric Acetate (CH3COOHgOOCCH3, abbreviated Hg(OAc)2) dissociates forming a +HgOAc ion, which bonds with the alkene to form a mercurinium cation with a three-membered ring (two carbons and the mercury atom, each one bonded to the other two). The alcohol (HO-R) then attacks this mercurinium ion at the more highly substituted of the two carbons that formerly made up the double bond. The addition of the alkoxy group, therefore, follows the Markovnikov rule. The HgOAc group remains bonded to the less substituted carbon. It is then removed (hence the "demercuration") by the reducing agent NaBH4, sodium borohydride, which replaces it with a hydrogen.
C=C + Hg(OAc)2 ==ROH==> RO-C-C-HgOAc ==NaBH4==> RO-C-C-H
--mark