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Basics of Organic Chemistry question

2019 · 10 Apr · Shift 2 · Q1
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Basics of Organic Chemistry question

2019 · 10 Apr · Shift 2 · Q1

JEE MainChemistryBasics of Organic ChemistryMCQ+4 / −1
The increasing order of nucleophilicity of the following nucleophiles is : (a) CH3CO2CH_3CO_2CH3​CO2​ −-− (b) H2OH_2OH2​O (c) CH3SO3CH_3SO_3CH3​SO3​ −-−(d) O−H\mathop O\limits^ - HO−​H
  1. A
    (b) < (c) < (a) < (d)
  2. B
    (b) < (c) < (d) < (a)
  3. C
    (a) < (d) < (c) < (b)
  4. D
    (d) < (a) < (c) < (b)
View written solutionFree

Correct answer: A

  1. Identify the nucleophiles

We are given:

  • (a) CH3CO2−CH_3CO_2^-CH3​CO2−​ = acetate ion
  • (b) H2OH_2OH2​O = water
  • (c) CH3SO3−CH_3SO_3^-CH3​SO3−​ = mesylate ion
  • (d) OH−OH^-OH− = hydroxide ion

We need the increasing order of nucleophilicity.

  1. Use the basic idea: nucleophilicity generally parallels basicity

For nucleophiles attacking through oxygen in the same period, stronger base is usually the stronger nucleophile, unless strong resonance stabilization reduces reactivity.

So let us compare:

(b) H2OH_2OH2​O

  • Neutral species
  • Much less nucleophilic than negatively charged oxygen species

Hence, H2OH_2OH2​O should be the weakest among these.

  1. Compare the anions

(d) OH−OH^-OH−

  • Negative charge localized on oxygen
  • Strong base
  • Therefore strong nucleophile

(a) CH3CO2−CH_3CO_2^-CH3​CO2−​

  • Acetate ion
  • Negative charge is resonance stabilized over two oxygens
  • Resonance reduces electron density available for donation
  • So it is less nucleophilic than OH−OH^-OH−

(c) CH3SO3−CH_3SO_3^-CH3​SO3−​

  • Mesylate ion
  • Negative charge is even more strongly delocalized over the sulfonate group
  • Sulfonate ions are very weak bases and very poor nucleophiles
  • Thus it is weaker than acetate

So among the anions: CH3SO3−<CH3CO2−<OH−CH_3SO_3^- < CH_3CO_2^- < OH^-CH3​SO3−​<CH3​CO2−​<OH−

  1. Combine with water

Since neutral water is weaker than these anions: H2O<CH3SO3−<CH3CO2−<OH−H_2O < CH_3SO_3^- < CH_3CO_2^- < OH^-H2​O<CH3​SO3−​<CH3​CO2−​<OH−

Thus, (b)<(c)<(a)<(d)(b) < (c) < (a) < (d)(b)<(c)<(a)<(d)

  1. Match with the options

Option A: (b)<(c)<(a)<(d)(b) < (c) < (a) < (d)(b)<(c)<(a)<(d) ✅

So the correct answer is A.

  1. Check with stored correct answer

Stored correct answer: A

This matches our derived answer.

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