Question

Which of the following is a method of preparing a primary alcohol ?

• A. Reduction of ketone
• B. Hydrolysis of the adduct obtained from a Grignard reagent and ethanal
• C. Oxidative alkaline hydrolysis of adduct obtained from an alkene and borane
• D. Hydrolysis of adduct obtained from a Grignard Reagent and a ketone

Answer 1

The correct option is C Oxidative alkaline hydrolysis of adduct obtained from an alkene and borane

c. A primary alcohol can be obtained by oxidative alkaline hydrolysis of adduct obtained from an alkene and borane.
$\underset{\text{Trialkyl borane}}{(C{H}_{3}C{H}_{2}C{H}_2{)}_{3}B}\underset{O{H}^{-}}{\overset{H_2{O}_2}{\to }}\underset{\text{propanol}}{C{H}_{3}C{H}_{2}C{H}_{2}OH}$
Hence option (c) is correct.
The above given reaction is known as hydroboration-oxidation reaction. If the reaction involves ​unsymmetrical alkenes​, it follows anti markovnikov's rule.

a. Reduction of ketone gives secondary alcohol.
Grignard reagent is a strong nucleophile. It undergoes nucleophilic addition reaction when it reacts with aldehyde, ester and ketone.
b. Hydrolysis of the adduct obtained from a Grignard reagent and ethanal gives secondary alcohol.
d. Hydrolysis of adduct obtained from a Grignard Reagent and a ketone gives tertiary alcohol.