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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3g2274

The compound shown is a 1,3-diketone. Select ALL the correct statements.

  1. AIts enol content is lower than that of acetone.
  2. BIts enol form is stabilised by an intramolecular hydrogen bond.
  3. CThe enol form gives a coloured complex with neutral ferric chloride.
  4. DIts enol form has a conjugated C=C-C=O system.

Answer: B, C, D

Pentane-2,4-dione exists largely as the Z-enol, which is stabilised by conjugation (C=C-C=O) and an intramolecular O-H...O hydrogen bond; the enol gives a red/violet complex with neutral FeCl3 as enols do. Its enol content (about 80%) is far higher than that of acetone, so the last statement is false.
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