JEE Main · 2025 · Shift-IhardHALO-131

Given below are two statements: Statement-I: The conversion proceeds well in the less polar medium.…

Haloalkanes & Haloarenes · Class 12 · JEE Main Previous Year Question

Question

Given below are two statements:

Statement-I: The conversion proceeds well in the less polar medium. CH3CH2CH2CH2Cl→HO−CH3CH2CH2CH2OH+Cl−\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{Cl} \xrightarrow{\text{HO}^-} \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{OH} + \text{Cl}^-

Statement-II: The conversion proceeds well in the more polar medium. CH3CH2CH2CH2Cl→R3N..CH3CH2CH2CH2N+R3Cl−\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{Cl} \xrightarrow{\text{R}_3\overset{..}{\text{N}}} \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{N}^+\text{R}_3\text{Cl}^-

(a) Both statement I and statement II are true (b) Both statement I and statement II are false (c) Statement I is false but statement II is true (d) Statement I is true but statement II is false

Options
  1. a

    Both statement I and statement II are true

    ✓
  2. b

    Both statement I and statement II are false

  3. c

    Statement I is false but statement II is true

  4. d

    Statement I is true but statement II is false

Correct Answera

Both statement I and statement II are true

Detailed Solution

Statement I — SN2 with OH⁻:

R-Cl+OH−→R-OH+Cl−\text{R-Cl} + \text{OH}^- \rightarrow \text{R-OH} + \text{Cl}^-

Reactants: charged (OH⁻, high charge density) Transition state: [HO⋯C⋯Cl]−[\text{HO}\cdots\text{C}\cdots\text{Cl}]^- — charge dispersed (lower charge density)

A less polar solvent better stabilises the dispersed-charge TS relative to the concentrated-charge reactant → reaction proceeds faster in less polar medium → ✅ TRUE

Statement II — Menshutkin reaction (SN2):

R-Cl+R3N→[R3N+⋯C⋯Cl−]‡→R3N-R++Cl−\text{R-Cl} + \text{R}_3\text{N} \rightarrow [\text{R}_3\overset{+}{\text{N}}\cdots\text{C}\cdots\text{Cl}^-]^{\ddagger} \rightarrow \text{R}_3\overset{+}{\text{N-R}} + \text{Cl}^-

Reactants: neutral (low charge density) Transition state: charge developing (higher charge density) Products: ionic (highest charge density)

A more polar solvent stabilises the charge-developing TS → lowers activation energy → reaction proceeds faster in more polar medium → ✅ TRUE

Answer: (a) Both statements are true

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