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Friday, 9 October

JEE Main 2020 · ChemistryMultiple choiceOtherMediumConceptual

JEE Main 8 January 2020, Shift 1, Chemistry Q44

Question 44 of 75 in this shift, Chemistry question 19 of 25, Section A.

The decreasing order of reactivity towards dehydrohalogenation (E1\mathrm{E_1}) reaction of the following compounds is : (A) CH3CH2CH2CH2CH2Cl\mathrm{CH_3CH_2CH_2CH_2CH_2Cl} (1-chloropentane, skeletal) (B) ClCH2CH2CH2CH=CH2\mathrm{ClCH_2CH_2CH_2CH{=}CH_2} (5-chloropent-1-ene, skeletal) (C) CH3CH(Cl)CH2CH3\mathrm{CH_3CH(Cl)CH_2CH_3} (2-chlorobutane, skeletal) (D) CH3CH(Cl)CH=CH2\mathrm{CH_3CH(Cl)CH{=}CH_2} (3-chlorobut-1-ene, skeletal)

The figure, in words

Four skeletal structures (A)-(D): (A) Cl on the end carbon of an unbranched five-carbon chain; (B) Cl on the end carbon of a five-carbon chain with a terminal C=C at the other end; (C) Cl on C-2 of butane; (D) Cl on C-3 of but-1-ene (allylic).
  1. (1)B > D > C > A
  2. (2)D > B > C > AOfficial answer
  3. (3)B > A > D > C
  4. (4)B > D > A > C

Official answer

Option 2

NTA final key (Jan 2020).

Chapter
Haloalkanes and Haloarenes
Topic
No close match in our taxonomy
Idea tested
No close match in our taxonomy

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.