MCQEasyJEE 2025Reaction Mechanisms (Substitution, Addition, Elimination)

JEE Chemistry 2025 Question with Solution

Given below are two statements:

Statement I: The conversion proceeds well in a less polar medium. CH3CH2CH2CH2ClHOCH3CH2CH2CH2OH+ClCH_3CH_2CH_2CH_2Cl \xrightarrow{HO^-} CH_3CH_2CH_2CH_2OH + Cl^-

Statement II: The conversion proceeds well in a more polar medium. CH3CH2CH2CH2ClR3NCH3CH2CH2CH2NH2+ClCH_3CH_2CH_2CH_2Cl \xrightarrow{R_3N} CH_3CH_2CH_2CH_2NH_2 + Cl^-

In the light of the above statements, choose the correct answer from the options given below:

  • 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

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: Two statements about the solvent preference of the reactions of CH3CH2CH2CH2ClCH_3CH_2CH_2CH_2Cl are to be evaluated.

Find: Which statement(s) is/are true.

For Statement I:

CH3CH2CH2CH2ClHOCH3CH2CH2CH2OH+ClCH_3CH_2CH_2CH_2Cl \xrightarrow{HO^-} CH_3CH_2CH_2CH_2OH + Cl^-

This is described as an SN2S_N2 nucleophilic substitution involving HOHO^- as the nucleophile. The extracted solution states that in SN2S_N2 reactions, less polar solvents are preferred because strongly polar solvents can stabilize the nucleophile and reduce its reactivity. Therefore, Statement I is true.

For Statement II:

CH3CH2CH2CH2ClR3NCH3CH2CH2CH2NH2+ClCH_3CH_2CH_2CH_2Cl \xrightarrow{R_3N} CH_3CH_2CH_2CH_2NH_2 + Cl^-

The extracted solution states that a more polar medium facilitates this transformation by stabilizing polar reactants and intermediates. Therefore, Statement II is true.

Hence, both statements are true. The correct option is A.

Common mistakes

  • Assuming that all nucleophilic substitution reactions always proceed faster in more polar solvents is incorrect. Solvent effect depends on the mechanism and the nature of the nucleophile, so the specific reaction conditions must be checked.

  • Ignoring the role of nucleophile solvation is a common error. If the nucleophile is strongly stabilized by the solvent, its reactivity can decrease; instead, relate solvent polarity to nucleophile strength and reaction mechanism.

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