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Alcohols, Phenols, and Ethers — Chemistry STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceChemistryAlcohols, Phenols, and Ethers1 Mark
Question
What is meant by hydroboration$-$oxidation reaction? Illustrate it with an example.
✓

Answer

The addition of borane followed by oxidation is known as the hydroboration$-$oxidation reaction.
In the first step, alkene reacts with diborane $\ce{(B_2H_6)}$ as boron hydride $\ce{(BH_3)}$ to form an alkyl borane.
In the next step, the alkyl borane is oxidised by alkaline $\ce{H_2O_2}$ to form an alcohol.
The indirect hydration proceeds according to Anti Markovnikoff’s rule.
For example,
$\text{3CH}_3\text{CH}=\text{CH}_2+\text{BH}_3\ \ \xrightarrow{\ \ \ \ }\ \ (\text{CH}_3\text{CH}_2\text{CH}_2)_3\text{B}\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Tri-n-Propyl borate}\\ \ \ \ \ \ \ \ \ \ \ \ \\ \ \\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \xrightarrow[\text{H}_2\text{O}]{\text{H}_2\text{O}_2/\text{OH}^-}\text{3CH}_3\text{CH}_2\text{CH}_2\text{OH}+\text{H}_3\text{BO}_3\\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \text{Propan-1-ol}\ \ \ \ \ \ \ \ \ \ \ \text{Boric acid}$

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