Question

a) Explain aldol condensation taking CH₂-CHO example.

b) Write the named reactions involved in the following conversions:

c) How are the following conversions achieved?

Answer 1

a) Aldehydes and ketones having at least one α-hydrogen undergo a reaction in the presence of dilute alkali as catalyst to form β-hydroxy aIde hydes (aldol) or β-hydroxy ketones (ketol), respectively. This is known asAldol reaction. The aldol and ketol readily lose water to give α, β unsaturated carbonyl compounds which are al-dol condensation products and the reaction is called Aldol condensation.

e.g. CH₃-CHO undergo Aldol reaction in presence of dil NaOH to form 3-Hydroxybutanal which on heating lose water to form the Aldol condensation product But-2-enal.

b) i) Rosenmund reduction

ii) Cannizzaro reaction