Question

Acetaldehyde and benzaldehyde can be differentiated by :

• A. Fehling test
• B. Iodoform test
• C. Tollen's reagent
• D. both (a) and (b)

Answer 1

The correct option is D both (a) and (b)

(Refer to Image 1)

For iodoform test one methyl must be there with carbonyl group. Thus acetaldehyde will give iodoform test and benzaldehyde does not.

(Refer to Image 2)

In Fehling test, enolate formation takes place, thus Aldehydes that lack alpha hydrogen cannot form an enolate and thus do not give a positive Fehling's test.

Thus Benzaldehyde do not give Fehling test as it do not have $\alpha -$ Hydrogen. While Acetaldehyde have $3\alpha -$Hydrogen thus it can form enolate and undergo Fehling test.

Thus Benzaldehyde & Acetaldehyde can be differentiated using Iodoform and Fehling test.