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JEE Advanced levelSingle correct optionDifficulty 3 of 3g2201

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 $K_{T} = [enol] / [keto]$ , is closest to

A $6.5$
B $32$
C $0.0055$
D $183$

Answer: D

K_{T} = % enol / (100 - % enol)

. In cyclohexane

K_{T} = 97/3 = 32.3

. In water

K_{T} = 15/85 = 0.176

. Ratio

= 32.3/0.176 = 183

. The ratio of percentages (

6.5

) is a common error, as it ignores that

K_{T}

compares enol with keto.

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