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When going through the preparation of alcohols, I came across the method of Oxymercuration-Demercuration.

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Now, after going over the reaction, I didn't understand the purpose of the mercuric acetate in this reaction. According to me, H2O should be able to dissociate into H+ and OH- and then break the double bond and attach itself to the alkane. But, this does not happen because of some reason that I'm not aware of.

Image source: https://en.wikipedia.org/wiki/Oxymercuration_reaction

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    $\begingroup$ Your alkene would hardly dissolve in water, much less get protonated. One needs strong acid or other catalyst, like Hg(II). $\endgroup$
    – Mithoron
    Sep 19 at 20:57
  • $\begingroup$ It does not happen because you need a very much stronger acid. This is easily searched for using your favourite web-search tool $\endgroup$
    – Waylander
    Sep 19 at 21:53

1 Answer 1

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Alkene is a nucleophile, while water also is a nucleophile so they don't interact with each other directly, so we need something to alter alkene's property. Mercuric acetate forms a cyclic intermediate with 2 carbons of alkene where Hg has a positive charge, so it really needs that bonded electrons back. This makes the carbon site partially positive, thus it now welcomes water and oxygen donates its lone pair to the carbon while the mercury atom withdraws the electron, here the latter process is faster. Thus the process is SN2 where the transition state has a carbocation character, so now we get the intermediate that is shown in the diagram.

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