Which of the following represents the most favored enol tautomer of ${\mathrm{CH}}_3\mathrm{COCH}{3}_{}$ (acetone)?

• A. ${\mathrm{CH}}_3\mathrm{CH}=\mathrm{COH}$
• B. ${\mathrm{CH}}_2=C\left(\mathrm{OH}\right){\mathrm{CH}}_3$
• C. ${\mathrm{CH}}_3\mathrm{COCH}{3}_{}$
• D. ${\mathrm{CH}}_3\mathrm{COHCH}{3}_{}$

Answer: (B)

Verified step by step guidance

1. Identify the keto and enol forms of acetone. The keto form is CH\_3COCH\_3, where the carbonyl group (C=O) is present. The enol form involves a C=C double bond adjacent to an OH group.
2. Understand tautomerism: keto-enol tautomerism is an equilibrium between a ketone (or aldehyde) and its corresponding enol. The enol form has a hydroxyl group (-OH) bonded to a carbon-carbon double bond.
3. Draw the enol form of acetone by moving a proton from the alpha carbon (adjacent to the carbonyl) to the oxygen of the carbonyl group, and forming a double bond between the alpha carbon and the carbonyl carbon. This gives CH\_2= C(OH)CH\_3.
4. Consider the stability factors: the keto form is generally more stable due to the strength of the C=O double bond compared to the C=C bond and the O-H bond in the enol. However, the most favored enol tautomer is the one that can be stabilized by resonance or intramolecular hydrogen bonding.
5. Conclude that the most favored enol tautomer of acetone is CH\_2= C(OH)CH\_3, where the double bond is between the alpha carbon and the carbonyl carbon, and the hydroxyl group is attached to the carbonyl carbon.