Question

In the presence of dil.NaOH, two molecules of an aldehyde may condense to form:

• A. an acid
• B. a -hydroxy aldehyde
• C. a -hydroxy ketone
• D. an alcohol

Answer 1

Answer: (B)

In the presence of dilute base or dilute acid, two molecules of an aldehyde or ketone, condense to form $\beta$ -hydroxy aldehyde or $\beta$ -hydroxy ketone respectively. This reaction is called Aldol condensation. $\underset{\text{Acetaldehyde}\text{(2}\text{molecules)}}{C{H}_3--\stackrel{H}{\stackrel{|}{C}}==O+H.C{H}_2--\stackrel{O}{\stackrel{||}{C}}--H\stackrel{dil.NaOH}{\to }}$ $\underset{\text{Aldol}}{C{H}_3--\underset{OH}{\stackrel{H}{\underset{|}{\stackrel{|}{C}}}}--C{H}_2}--CHO$