Statement 1 : The enol content of pentane-2,4-dione is much higher than that of propanone.
Statement 2 : The enol form of pentane-2,4-dione is stabilised by conjugation of $C = C$ with $C = O$ and by intramolecular hydrogen bonding.

Question

Statement 1 : The enol content of pentane-2,4-dione is much higher than that of propanone.

Statement 2 : The enol form of pentane-2,4-dione is stabilised by conjugation of $C = C$ with $C = O$ and by intramolecular hydrogen bonding.

TestHub · Accepted Answer

Statement 1 is true: pentane-2,4-dione is about 80% enol while propanone has only about $1 0^{- 4}$ % enol.

Statement 2 is true: the enol of pentane-2,4-dione has a conjugated $C = C - C = O$ system and a six-membered ring formed by an O–H···O hydrogen bond. Propanone's enol has neither.

These two stabilising factors are exactly why the enol content is high, so statement 2 explains statement 1.

Answer: (A).

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