Question

Convert the following:

Acetaldehyde to But-2-enal

Answer 1

Aldol condensation (in presence of dil. $$\mathrm{NaOH}$$) followed by dehydration.

$$\begin{array}{c}\phantom{}\underset{\mathrm{Acetaldehyde}}{\mathrm{CH}{\phantom{A}}_3\mathrm{CHO}}\stackrel{\mathrm{dil}\cdot \mathrm{NaOH}}{\to }\mathrm{CH}{\phantom{A}}_3-\mathrm{CH}-\mathrm{CH}{\phantom{A}}_2-\mathrm{CHO}\underset{-\mathrm{H}{\phantom{A}}_2\mathrm{O}}{\overset{\mathrm{\Delta }}{\to }}\underset{\underset{(\mathrm{Adol}\mathrm{condensation}\mathrm{product})}{\mathrm{But}\text{-}2\text{-}\mathrm{enal}}}{\mathrm{CH}{\phantom{A}}_3-\mathrm{CH}}=\mathrm{CH}-\mathrm{CHO}\\ |\phantom{.........................}\\ \underset{\underset{(\mathrm{Adol})}{3\text{-}\mathrm{Hydroxybutanal}}}{\mathrm{OH}}\phantom{.......................}\end{array}$$