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JEE Main levelOne or more correct optionsDifficulty 2 of 3g2258

The compound shown is a beta-ketoester. Select ALL the correct statements.

  1. AIts pKa is lower than that of diethyl malonate.
  2. BThe OCH2CH3 hydrogens are about as acidic as the CH2 hydrogens.
  3. CThe CH2 hydrogens between the two carbonyl groups are the most acidic.
  4. DThe conjugate base has charge delocalised onto both carbonyl oxygens.

Answer: A, C, D

The compound is ethyl acetoacetate. Its CH2 hydrogens (pKa about 11) are the most acidic and lie between a ketone and an ester C=O. The anion is delocalised over both carbonyl oxygens, and the compound is more acidic than diethyl malonate (about 13) because a ketone stabilises the carbanion better than an ester. The ethoxy CH3 hydrogens are not activated.
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