CH 8-2 Acid-Catalyzed Electrophilic Addition of H2O and ROH to Alkenes

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Presentation transcript:

CH 8-2 Acid-Catalyzed Electrophilic Addition of H2O and ROH to Alkenes (1) Electrophilic Addition of HX (HCl & HBr) -Carbocation mechanism -Regioselective: Markovnikov’s Rule -Non-stereospecific reaction -Rearrangements possible (2) Electrophilic Addition of H2O and ROH -Acid catalysis -Carbocation mechanism -Rearrangements possible (3) Electrophilic Addition of Br2 and Cl2 to alkenes -”Halonium ion” mechanism -No carbocation -Stereospecific reaction

Mechanism of H2O Addition: Alkene Hydration (1) H2SO4 (strong acid) provides a reactive H+ electrophile. (2) A carbocation is formed (non-stereospecific) giving a racemic mixture; rearrangements are possible. (3) H2O is the nucleophile, and an acid/base neutralization step is needed to give neutral alcohol product and to regenerate the acid catalyst.

Mechanism of H2O Addition: Alkene Hydration