Tautomerism and enol content

28 questions on Tautomerism and enol content from the General Organic Chemistry II: Acids and Bases chapter: 7 NEET level, 11 JEE Main, 10 JEE Advanced. Each one opens with its answer and solution.

• Which of the following compounds can exhibit keto-enol tautomerism? NEET level
• Phenol exists almost entirely in the enol form rather than as its keto tautomer, cyclohexa-2,4-dien-1-one. The main reason is that NEET level
• The number of alpha hydrogens in butan-2-one, CH3CH2COCH3, is NEET level
• Which of the following shows nitro-aci tautomerism? NEET level
• Which of the following has the highest enol content at equilibrium? NEET level
• The imidic acid tautomer of acetamide, CH3CONH2, is NEET level
• Which of the following is a tautomer of propanone? NEET level
• Which order correctly gives the enol content of the following compounds? JEE Main level
• Butan-2-one, CH3COCH2CH3, can enolise toward either alpha carbon. The total number of enol tautomers, counting geometrical (cis/trans) isomers as separate, is JEE Main level
• Cyclohexane-1,3-dione is largely enolic in solution, unlike cyclohexanone, whose enol content is negligible. The chief reason is that the enol JEE Main level
• Hexane-2,4-dione has a higher enol content in hexane than in water. This is because JEE Main level
• The total number of alpha hydrogens in ethyl acetoacetate, CH3COCH2COOC2H5, is JEE Main level
• The aci form of nitroethane, CH3CH2NO2, is JEE Main level
• Assertion (A): Pentane-2,4-dione has a much higher enol content than propanone. Reason (R): The enol of pentane-2,4-dione is stabilised by conjugation of C=C wi... JEE Main level
• The enamine tautomer of the imine CH3CH2CH=NCH3 is JEE Main level
• 5-Hydroxypentanal exists in equilibrium with a cyclic ring-chain tautomer formed by addition of the hydroxyl group to the aldehyde group. The ring tautomer is JEE Main level
• How many of the following compounds can undergo keto-enol tautomerism? CH3CHO, C6H5CHO, C6H5COCH3, (CH3)3C-CO-C(CH3)3, CH3COCH(CH3)2, HCHO JEE Main level
• For a ketone at equilibrium in a given solvent, the tautomerisation constant is K_T = [enol]/[keto] = 0.37. Calculate the percent enol content at equilibrium, t... JEE Main level
• A 1.300 g sample of ethyl acetoacetate (M=130 g mol^-1) is dissolved in methanol and made up to exactly 100.0 mL. A 10.0 mL aliquot is titrated rapidly with 0.0... JEE Advanced level
• 2-Methylcyclohexanone can enolise toward C-2 or C-6. Counting every distinct enol tautomer, including stereoisomers (enantiomers count separately), the total is JEE Advanced level
• The enol content of pentane-2,4-dione is 97% in cyclohexane and 15% in water (illustrative values). The ratio K_T(cyclohexane)/K_T(water), where K_T=[enol]/[ket... JEE Advanced level
• In non-polar hexane, the dominant species of pentane-2,4-dione is JEE Advanced level
• Which of the following factors increase the enol content of a carbonyl compound? JEE Advanced level
• Which of the following can show nitro-aci tautomerism? JEE Advanced level
• Which of the following give a coloured complex with neutral FeCl3 solution? JEE Advanced level
• Which of the following statements about enol content are correct? JEE Advanced level
• Which of the following pairs are tautomers of each other? JEE Advanced level
• For butan-2-one, CH3COCH2CH3, which statements are correct? JEE Advanced level