Illustrated Glossary of Organic Chemistry

Hydroboration-oxidation reaction: A reaction in which an alkene or alkyne suffers hydroboration to give an organoborane, This organoborane is oxidized to give an alcohol (when the reactant is an alkene), a ketone (when the reactant is an internal alkyne), or an aldehyde (when the reactant is a terminal alkyne). The net effect is the addition of a molecule of water across the carbon-carbon pi bond.

Steps in Hydroboration-Oxidation of an Alkene


Borane (BH3) adds to methylcyclohexene in a syn manner to give an organoborane.


Oxidation of the organoborane with base and hydrogen peroxide converts the carbon-boron bond into an alcohol. Stereochemistry at the carbon atom that was bonded to the boron atom is retained. The net effect of the reaction is syn, anti-Markovnikov addition of water to the alkene pi bond.

Steps In Hydroboration-Oxidation of an Alkyne


Borane (BH3) adds to propyne (a terminal alkyne) in a syn manner to give a vinylic organoborane.


Oxidation of the vinylic organoborane with base and hydrogen peroxide converts the carbon-boron bond into an alcohol, resulting in an enol.


Base-catalyzed tautomerization converts the enol into an aldehyde.