HYDROBORATION OF ALKENES

HYDROBORATION OF ALKENES - slightly electron-deficient,...

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HYDROBORATION OF ALKENES - anti-Markovnikov product First step is the attack of the alkene on BH 3 , which then forms a 4-membered ring intermediate of partial bonds. It is because of this intermediate that hydroboration forms the anti- Markovnikov product . The B atom is highly electrophilic because of its empty p orbital (i.e. it wants electrons), and forms a slight bonding interaction with the pi bond. Since some electron density from the double bond is going towards bonding with the B, the C opposite the B is
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Unformatted text preview: slightly electron-deficient, left with a slightly positive charge. Positive charges are best stabilized by more highly substituted carbons, so the C opposite the B tends to be the most highly substituted. Once the transition state breaks down, BH 2 is attached to the least substituted C. Peroxide then removes the borane and replaces it with the alcohol to form the anti-Markovnikov product. Example of the hydroboration mechanism:...
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This note was uploaded on 03/21/2008 for the course CHEM 261 taught by Professor Austell during the Spring '08 term at UNC.

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