Question

Which reagent converts propene to propan - 1 - ol?
a) ${H}_{2}O, {H}_{2}S{O}_{4}$
b) ${B}_{2}{H}_{6}, {H}_{2}{O}_{2}, O{H}^{-}$
c) $Hg{(OAc)}_{2}, NaB{H}_{4}/{H}_{2}O$
d) Aq. $KOH$

Answer 1

Hint: Alkenes can be converted to alcohols by various methods. One such method to convert alkene to alcohol is through the hydroboration-oxidation reaction.

Complete step by step answer:
In hydroboration-oxidation reaction a two-step hydration reaction takes place that converts an alkene into an alcohol. The process results in the syn addition of a hydrogen and a hydroxyl group where the double bond had been present.
Thus, Propan-1-ol is produced by the hydroboration-oxidation reaction of propene.

In this reaction, propene reacts with diborane ${B}_{2}{H}_{6}$ to form trialkyl borane as an additional product. The product thus formed is oxidized to alcohol by hydrogen peroxide in the presence of aqueous sodium hydroxide.
$\underset { Propene }{ { C }_{ 3 }{ H }_{ 6 } } \quad +\quad \underset { Diborane }{ { B }_{ 2 }{ H }_{ 6 } } \quad \longrightarrow \quad { C }_{ 3 }{ H }_{ 7 }{ B }{ H }_{ 2 }$

${ C }_{ 3 }{ H }_{ 7 }{ B }{ H }_{ 2 }\quad +\quad \underset { Propene }{ { C }_{ 3 }{ H }_{ 6 } } \quad \longrightarrow \quad { { (C }_{ 3 }{ H }_{ 7 }) }_{ 2 }BH$

$\quad { { (C }_{ 3 }{ H }_{ 7 }) }_{ 2 }BH\quad +\quad \underset { Propene }{ { C }_{ 3 }{ H }_{ 6 } } \quad \longrightarrow \quad { ({ C }_{ 3 }{ H }_{ 7 }) }_{ 3 }B$

${ ({ C }_{ 3 }{ H }_{ 7 }) }_{ 3 }B\quad \xrightarrow [ { H }_{ 2 }O,\quad 3{ H }_{ 2 }{ O }_{ 2 } ]{ O{ H }^{ - } } \quad \underset { Propan-1-ol }{ 3{ C }_{ 3 }{ H }_{ 7 }OH } \quad +\quad B{ (OH) }_{ 3 }$

 Therefore, The reagents that convert propene into propan - 1 - ol are ${B}_{2}{H}_{6}, {H}_{2}{O}_{2}, O{H}^{-}$.

Hence, option (b) is the correct answer.

Additional Information:
1. Diborane is a colorless, pyrophoric gas that has a repulsively sweet odor. Diborane and its variants are central organic synthesis reagents for hydroboration, whereby alkenes add across the B-H bonds to give trialkylboranes.
2. Hydrogen peroxide is a very pale blue liquid, slightly more viscous than water. Hydrogen peroxide is the simplest peroxide. Hydrogen peroxide can easily break down, or decompose, into water and oxygen by breaking up into two very reactive parts.
3. Diborane is used as a reducing agent. The compound readily reduces carboxylic acids to the corresponding alcohols, whereas ketones react only sluggishly.
4. Hydrogen peroxide is used as an oxidizer, bleaching agent, and antiseptic.

Note: Diborane is toxic in nature which is due to its irritant properties. Short-term exposure to diborane can cause a sensation of tightness of the chest, shortness of breath, cough, and wheezing.