Alkene Reaction and Hydroboration-Oxidation

Diborane (BH3 )2 reacts with alkenes to give trialkyl boranes, which are then oxidized to alcohols by hydrogen peroxide in the presence of aqueous sodium hydroxide. The addition of borane to the double bond takes place in such a manner that the boron atom gets attached to the sp 2 carbon carrying greater number of hydrogen atoms, resulting in the formation of alcohol in a way opposite to the Markovnikov’s rule.

Aldehydes and ketones are reduced to alcohols by addition of hydrogen in the presence of catalysts (catalytic hydrogenation). The usual catalyst is a finely divided metal such as platinum, palladium or nickel. They can also be reduced by treating with sodium borohydride (NaBH4 ) or lithium aluminium hydride (LiAlH4 ).

Hydrogen peroxide in the presence of aqueous sodium hydroxide oxidizes the trialkyl boranes formed in the hydroboration step to alcohols.

<p>The addition of borane to the double bond takes place in such a manner that the boron atom gets attached to the sp 2 carbon carrying greater number of hydrogen atoms, resulting in the formation of alcohol in a way opposite to the Markovnikov’s rule.</p> Signup and view all the answers

<p>Aldehydes and ketones can be reduced to alcohols by treating with sodium borohydride (NaBH4 ) or lithium aluminium hydride (LiAlH4 ).</p> Signup and view all the answers

<p>Diborane (BH3)2 = Hydroboration–oxidation Sodium borohydride (NaBH4) or lithium aluminium hydride (LiAlH4) = Reduction of aldehydes and ketones Hydrogen in the presence of catalysts (catalytic hydrogenation) = Reduction of aldehydes and ketones Hydrogen peroxide in the presence of aqueous sodium hydroxide = Hydroboration–oxidation</p> Signup and view all the answers

<p>Trialkyl boranes = Hydroboration–oxidation Primary alcohols = Reduction of aldehydes and ketones Aldehydes and ketones = Reduction of aldehydes and ketones Alkenes = Hydroboration–oxidation</p> Signup and view all the answers

<p>Platinum, palladium or nickel = Reduction of aldehydes and ketones Sodium borohydride (NaBH4) or lithium aluminium hydride (LiAlH4) = Reduction of aldehydes and ketones Diborane (BH3)2 = Hydroboration–oxidation Hydrogen in the presence of catalysts (catalytic hydrogenation) = Reduction of aldehydes and ketones</p> Signup and view all the answers

<p>Alcohol is obtained in excellent yield = Hydroboration–oxidation Alcohol looks as if it has been formed by the addition of water to the alkene in a way opposite to the Markovnikov’s rule = Hydroboration–oxidation The addition of borane to the double bond takes place in such a manner that the boron atom gets attached to the sp2 carbon carrying greater number of hydrogen atoms = Hydroboration–oxidation Usual catalyst is a finely divided metal such as platinum, palladium or nickel = Reduction of aldehydes and ketones</p> Signup and view all the answers

<p>Alkenes = Hydroboration–oxidation Aldehydes and ketones = Reduction of aldehydes and ketones Diborane (BH3)2 = Hydroboration–oxidation Sodium borohydride (NaBH4) or lithium aluminium hydride (LiAlH4) = Reduction of aldehydes and ketones</p> Signup and view all the answers