Keto-enol tautomerism is not shown by

Step-by-step solution

The compounds A, B and C show keto-enol tautomerism. A. C H 3 - C | | O - C H 2 C H 3 ⇌ C H 3 - C = | O H C H - C H 3 i ⇌ H 2 C = C - | O H C H 2 C H 3 i i The first enol is more stable, because it has the more substituted double bond. B. P h C H 2 - C | | O - C H 2 - C H 3 ⇌ P h C H = C - | O H C H 2 - C H 3 i ⇌ P h C H 2 - C = | O H C H - C H 3 i i The first enol is more stable, because C = C and Ph are conjugated. C. p - O 2 N C 6 H 4 C H 2 C O C H 3 ⇌ p - O 2 N C 6 H 4 C H = C | - O H C H 3 ( i ) ⇌ p - O 2 N C