Question

What is the common group in both aldehydes and ketones? In what respects acetaldehyde resembles and differs with acetone? Give one reaction for each.

Answer 1

The common gp present in both aldehyde and ketone is divolent carbonyl gp i.e.< C = 0.

Both Acetaldehyde & Acetone give iodoform Test. Both reacts with I₂ and NaOH to give yellow PPt of Iodoform m.

CH₃CHO(Acetaldehyde) + 3I₂ + 4NaOH → HCl₃↓(Yellow ppt) + 3NaI + 3H₂O

CH₃COCH₃(Acetone) + 3I₂ + 4NaOH → HCl₃↓(Yellow ppt) + 3NaI + HCOONa + 3H₂O

where bothe Acetaldehyde and acetone differ with Tollen's reagent.

Acetaldehyde reacts with Ammoniated AgNO₃ soln reduced Ag metal which is called silver mirror. So this reaction is used for the test of Aldehyde gp & known as silver mirror.

CH₃CHO + Ag₂O → CH₃COOH + 2Ag↓ Silver mirro

However, Acetone does not gives any reaction with Tollens reagent.