JEE Main20264 April 2026Morning ShiftChemistryAlcohols Phenols and EthersActual
Identify the colour of compound 'X' in the sequence of the reaction.
Options
- AViolet
- BGreen
- CRed
- DColourless
Correct answer
D. Colourless
Step-by-step solution
The given reaction sequence represents the synthesis and acid-base behaviour of phenolphthalein. When phenol reacts with phthalic anhydride in the presence of concentrated H₂SO₄ , phenolphthalein is formed. In acidic or neutral medium, phenolphthalein exists in a lactone form which is colourless. Upon addition of a moderate amount of alkali (NaOH), the lactone ring opens and a proton is removed, forming a dianion with an extended conjugated quinonoid structure. This extended conjugation is responsible for the chara