Return to Contents Chapter 15: Alcohols, Diols and Thiols Ch 15 contents

Hydroboration / Oxidation of Alkenes
(review of Chapter 6)

hydroboration of C=C
Reaction type: Electrophilic Addition

Summary.

Related Reactions
MECHANISM FOR REACTION OF ALKENES WITH BH3
Step 1:
A concerted reaction. The p electrons act as the nucleophile with the electrophilic B and the H is transferred to the C with syn stereochemistry.
addition of HBr to C=C
Step 2:
First step repeats twice more so that all of the B-H bonds react with C=C
Step 3:
Peroxide ion reacts as the nucleophile with the electrophilic B atom.
Step 4:
Migration of C-B bond to form a C-O bond and displace hydroxide. Stereochemistry at the C center is unchanged i.e. it is retained.
Step 5:
Attack of hydroxide as a nucleophile with the electrophilic B displacing the alkoxide.
Step 6:
An acid / base reaction to form the alcohol.

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© Dr. Ian Hunt, Department of Chemistry, University of Calgary