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Saturday, 31 October

JEE Main 2022 · ChemistryMultiple choiceSingle correctMediumConceptual

JEE Main 28 July 2022, Shift 1, Chemistry Q74

Question 74 of 90 in this shift, Chemistry question 14 of 30, Section A.

Among the following marked proton of which compound shows lowest pKa\mathrm{pK_a} value ?

The figure, in words

Each option shows a structure with one underlined H.
  1. (1)H‾CH2−COOH\underline{\mathrm{H}}\mathrm{CH_2-COOH} (marked H on the CH2 carbon of CH3COOH\mathrm{CH_3COOH})
  2. (2)H‾CH2−C(=O)−CH3\mathrm{\underline{H}CH_2-C(=O)-CH_3} (marked H on a methyl of acetone)
  3. (3)[figure: PhCH(H marked)-C(=O)-CH3, marked alpha H of 1-phenylpropan-2-one]Official answer
  4. (4)[figure: PhCH(H marked)-C(=O)OH, marked alpha H of phenylacetic acid]

Official answer

Option 3

NTA final key (2022 Session 2).

Chapter
Organic Chemistry: Some Basic Principles and Techniques
Topic
Organic Acidity and Basicity
Idea tested
Acidity of Alpha-Hydrogens in Carbonyls

Same idea in other shifts

Asked 2× in all
  1. 5 Sep 2020, Shift 1 · Q30The increasing order of the acidity of the α\alpha-hydrogen of the following compounds is :MediumDiagram basedHas a figure

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.