Question

When 1 mole of ${\text{NaB}}{{\text{H}}_{\text{4}}}$ is used to reduce ketone, how many moles of hydride is used?

Answer 1

In the above question, it is asked that how many moles of hydride is used when 1 mole of ${\text{NaB}}{{\text{H}}_{\text{4}}}$ is used to reduce ketone. For this we have to first write a balanced chemical equation of reaction of ketone with ${\text{NaB}}{{\text{H}}_{\text{4}}}$ and then we can find the number of moles.

Complete step by step solution:
Let us first write the balanced chemical equation of reaction of ketone and ${\text{NaB}}{{\text{H}}_{\text{4}}}$ .
${\text{4}}{{\text{R}}_{\text{2}}}{\text{C = O + NaB}}{{\text{H}}_{\text{4}}} \to {{\text{(}}{{\text{R}}_{\text{2}}}{\text{CH - O)}}_{\text{4}}}{\text{BNa}}$
Here we can see that 4 moles of ketone reacts with 1 mole of ${\text{NaB}}{{\text{H}}_{\text{4}}}$ which implies that 1 mole of ketone reacts with ${\text{0}}{\text{.25}}$ moles of ${\text{NaB}}{{\text{H}}_{\text{4}}}$ .
Hence, when 1 mole of ${\text{NaB}}{{\text{H}}_{\text{4}}}$ is used to reduce ketone, ${\text{0}}{\text{.25}}$ moles of hydride is used.

Additional information:
Ketone is used in number of ways which includes:
The most common ketone is acetone which is an excellent solvent for a number of plastics and synthetic fibres.
In the household, acetone is often used as a nail paint remover and paint thinner.
In terms of medicinal uses, it is used in chemical peeling and for acne treatments.
Cyclohexanone which is a ketone is used for making nylon.

Note:
Sodium borohydride is a good reducing agent. Although not as powerful as lithium aluminum hydride, it is very effective for the reduction of aldehydes and ketones to alcohols. Only sodium borohydride cannot reduce esters, carboxylic acids, or amides but it can be used in the second step of the oxymercuration reaction to replace mercury with H.