NTA Abhyas NEET2020ChemistryCarboxylic Acid DerivativesPractice
One mL of an organic compound was dissolved in ethanol and a very small drop of dilute alkali was added to it and them a drop of phenolphthalein was added. The red colour of the indicator was seen. The mixture was then heated. The colour disappeared in a few minutes. The organic compound is most likely to be
Options
- Aan aldehyde
- Ba ketone
- Ca carboxylic acid
- Dan ester
Correct answer
D. an ester
Step-by-step solution
Phenolphthalein does not give any colour with a carboxylic acid containing a drop of dilute alkali. The red colour of the indicator indicates that alkali remains un-reacted before heating the compound. After heating, disappearance of red colour indicates the consumption of NaOH. This because the ester hydrolyses in presence of base to form alcohol and sodium salt of carboxylic acid. RCOOR ' + NaOH → Δ RCOONa + R ' OH