Tautomerism is due to spontaneous interconversion of two isomeric forms with differentfunctional groups into each other. The term tautomer means constitutional isomers thatundergo such rapid inter conversion that they cannot be independently isolated. In keto-enol tautomerism although Keto form in general is more stable, but some factors like H-bonding and extended double bonds conjugation may increase the stability of enol form Enolic form of acetyl acelone is stabilized due to (I) resonance as a result of conjugation (II) intra molecular H-bonding(III) dipole- dipole repulsion

Tautomerism is due to spontaneous interconversion of two isomeric form

1.	Tautomerism is due to spontaneous interconversion of two isomeric forms with differentfunctional groups into each other. The term tautomer means constitutional isomers thatundergo such rapid inter conversion that they cannot be independently isolated. In keto-enol tautomerism although Keto form in general is more stable, but some factors like H-bonding and extended double bonds conjugation may increase the stability of enol form Enolic form of acetyl acelone is stabilized due to (I) resonance as a result of conjugation (II) intra molecular H-bonding(III) dipole- dipole repulsion
Answer» I and III II and III I and II I only Solution :Due to two reasons there are 1) EXTEND of conjugation 2) intra molecular HYDROGEN BOND formation.