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Aldehydes, Ketones, and Carboxylic Acids — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryAldehydes, Ketones, and Carboxylic Acids3 Marks
Question
Give reasons:
  1. Propanone is less reactive than ethanal towards nucleophilic addition reactions.
  2. $O_2N – CH_2 – COOH$ has lower pKa value than $CH_3COOH.$
  3. $(CH_3)_2CH – CHO$ undergoes aldol condensation whereas $(CH_3)_3C – CHO$ does not.
✓

Answer

  1. Due to steric hindrance and $+I$ effect caused by two alkyl groups in propanone.
  2. Due to electron withdrawing nature of $–NO_2$ group which increases the acidic strength and decreases the $pK_a$ value.
  3. $(CH_3)_2CH-CHO$ has one $\alpha - H$ atom whereas $\alpha - H$ atom is absent in $(CH_3)_3C-CHO.$

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