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  • Alkenes do not undergo hydration upon treatment with water even at very high temperatures. There are two approaches to hydrating alkenes:

    1. Reaction of the alkene with water in the presence of a strong-acid catalyst.
    2. Using an indirect method

    Hydroboration-oxidation, sometimes casually called hydroboration for convenience, is a common indirect method used to hydrate alkenes.

    net reaction:

    The protocol is carried out in two stages:

    Stage 1: Hydroboration

    The alkene is treated with a source of borane ( diborane or borane-THF complex), which converts the alkene into a trialkylborane.

    Stage 2: Oxidation

    The trialkylborane is treated with H2O2 and a strong base, usually NaOH, in aqueous medium, which converts the trialkylborane into an alcohol.

    Stage 1:

    This reaction is an anti-Markovnikov addition and a syn addition.

    Stage 2:

    Stage 1 + Stage 2 =

    The net reaction is an anti-Markovnikov addition:

    see also oxymercuration-reduction

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