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JEE Main 2024 · Chemistry · Carbonyl Compounds, Carboxylic Acids and Amines · hard

Acetaldehyde is treated with excess formaldehyde in the presence of concentrated NaOH. The organic products formed are

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Acetaldehyde is treated with excess formaldehyde in the presence of concentrated NaOH. The organic products formed are
  1. A. C(CH2OH)4\mathrm{C(CH_2OH)_4} and HCOONa\mathrm{HCOONa}
  2. B. CH3CH(OH)CH2CHO\mathrm{CH_3CH(OH)CH_2CHO} only
  3. C. (HOCH2)3CCHO\mathrm{(HOCH_2)_3CCHO} and CH3OH\mathrm{CH_3OH}
  4. D. HOCH2CH2CH2OH\mathrm{HOCH_2CH_2CH_2OH} and HCOONa\mathrm{HCOONa}
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Answer: (A) C(CH2OH)4\mathrm{C(CH_2OH)_4} and HCOONa\mathrm{HCOONa}

Acetaldehyde has three α\alpha-hydrogens and formaldehyde has none, so three successive crossed aldol additions with HCHO give (HOCH2)3C−CHO(\mathrm{HOCH_2})_3\mathrm{C{-}CHO}. This aldehyde has no α\alpha-H and, in the presence of excess HCHO and strong base, undergoes crossed Cannizzaro reaction: HCHO is oxidised to formate and the hindered aldehyde is reduced to CH2OH\mathrm{CH_2OH}. The product is pentaerythritol, C(CH2OH)4\mathrm{C(CH_2OH)_4}, with sodium formate.
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