Which among the following compounds forms pink colouration on addition of Schiff's reagent?

Step-by-step solution

Schiff's reagent detects aldehydes by forming a pink coloration upon reaction. The reagent, prepared by decolorizing rosaniline hydrochloride with sulfur dioxide, remains colorless until an aldehyde is introduced. Analyzing the functional groups: Propanol is an alcohol, propanone a ketone, propanal an aldehyde, and propanoic acid a carboxylic acid. Since only aldehydes produce the characteristic pink color with Schiff's reagent, propanal ( CH₃ CH₂ CHO ) is the compound that reacts.