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Friday, 9 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 topic in other shifts

All Organic Acidity and Basicity questions
  1. 4 Apr 2026, Shift 1 · Q66Amongst the following, the total number of compounds soluble in aqueous NaOH at room temperature is:MediumDiagram basedHas a figure
  2. 4 Apr 2026, Shift 2 · Q66The descending order of acidity among the following compounds is: A. phenol B. 4-nitrophenol (O2N\mathrm{O_2N} para to OH on the benzene…MediumOtherHas a figure
  3. 3 Apr 2025, Shift 1 · Q67The least acidic compound, among the following is: (A) [structure: 3-ethoxyphenol, EtO and OH meta on a benzene ring] (B) [structure:…MediumDiagram basedHas a figure
  4. 7 Apr 2025, Shift 1 · Q68Which of the following compounds is least likely to give effervescence of CO2\mathrm{CO_2} in presence of aq. NaHCO3\mathrm{NaHCO_3} ?EasyDiagram basedHas a figure
  5. 8 Apr 2025, Shift 2 · Q61Match the LIST-I with LIST-II LIST-I (Reagent) | LIST-II (Functional Group detected) A. Sodium bicarbonate solution | I. double bond/…MediumMatch the list
  6. 31 Jan 2024, Shift 1 · Q77Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R: Assertion A: pKa\mathrm{pK_a} value…EasyAssertion–reason

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 42 of the 174 JEE Main shifts held from 2017 to 2026.