The conversion of a keto form into enol is enolisation. It depends on structural factor, temperature and nature of solvent. Resonance and hydrogen bonding increases enol content. Enolic form of phenol is more stable than keto form by-13 kcal/mol of energy hence phenol exist exclusively as an enol. Enolic tautomer is less polar due to intramolecular hydrogen bonds than the corresponding keto form. Any polar solvent would decrease the enolisation and fovour keto form intramolecular hydrogen bonding stabilized enol form by 7kcal/mol and resonance stabilizes enol form by 15 kcal/mole
Ketonic form predominates in
A. `CH_(3)-CO-CH_(3)`
B. `C_(6)H_(5)COCH_(2)COCH_(3)`
C. `CH_(3)-CO-CH_(2)-COCH_(3)`
D. `CH_(3)COCH_(2)COOC_(2)H_(5)`
