Chapter 19, Problem 19.76P

Interpretation Introduction

Interpretation:

Synthesis of $\text{hexan-3, 4-diol}$ from propanal is to be determined.

Concept introduction:

For the reduction of aldehyde to alcohol, ${\text{NaBH}}_{\text{4}}$ in the presence of ethanol is used.

For the conversion of bad leaving group (hydroxy group $\left(\text{OH}\right)$) into good leaving group like $\left(\text{Br}\right)$ bromine, ${\text{PBr}}_{\text{3}}$ is used. In this way, alcohol is converted into alkyl halide.

Alkyl halide is treated with triphenylphosphine $\text{P}{\left({\text{C}}_{\text{6}}{\text{H}}_{\text{5}}\right)}_{\text{3}}$ and a strong base like butyllithium $\left(\text{Bu-Li}\right)$, which results in the formation of Wittig reagent.

Reaction of Wittig reagent with aldehyde results in the formation of alkene product.

Reaction of alkene with $\text{m-CPBA}$ results in the formation of three membered epoxide ring.

The opening of the epoxide ring and formation of diol is carried out in the presence of acidic condition $\left({\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{, H}}_{\text{2}}\text{O}\right)$.