JEE Main · 2024 · Shift-ImediumHALO-036

The product (C) in the below mentioned reaction is:

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

Question

The product (C) in the below mentioned reaction is: image

Options
  1. a

    Propan-1-ol

  2. b

    Propene

  3. c

    Propyne

  4. d

    Propan-2-ol

Correct Answerd

Propan-2-ol

Detailed Solution

Step 1: Identify product A (elimination)

1-Bromopropane + heat (Δ) → elimination

With heat alone (no base), this likely means dehydrohalogenation or the question implies a base.

Assuming elimination with heat: \ceCH3CH2CH2Br>[Δ]CH3CH=CH2+HBr\ce{CH3-CH2-CH2Br ->[\Delta] CH3-CH=CH2 + HBr}

Product A = Propene (\ceCH3CH=CH2\ce{CH3-CH=CH2})

Step 2: Identify product B (addition of HBr)

Propene + HBr → addition following Markovnikov's rule

Markovnikov: H goes to carbon with more H, Br goes to more substituted carbon

\ceCH3CH=CH2+HBr>CH3CHBrCH3\ce{CH3-CH=CH2 + HBr -> CH3-CHBr-CH3}

Product B = 2-Bromopropane

Step 3: Identify product C (hydrolysis)

2-Bromopropane + aqueous KOH → nucleophilic substitution

\ceCH3CHBrCH3+KOH(aq)>CH3CH(OH)CH3+KBr\ce{CH3-CHBr-CH3 + KOH(aq) -> CH3-CH(OH)-CH3 + KBr}

Product C = Propan-2-ol (isopropanol)

Overall transformation: \ceCH3CH2CH2Br>CH3CH=CH2>CH3CHBrCH3>CH3CH(OH)CH3\ce{CH3CH2CH2Br -> CH3CH=CH2 -> CH3CHBrCH3 -> CH3CH(OH)CH3}

1-Bromopropane → Propene → 2-Bromopropane → Propan-2-ol

Answer: (d)

Key Reactions:

  1. Elimination (Δ): Alkyl halide → Alkene
  2. Markovnikov addition: HX adds to alkene (H to less substituted C)
  3. Nucleophilic substitution: Alkyl halide + OH⁻ → Alcohol

Note: This sequence converts a primary alcohol position to a secondary alcohol position via elimination-addition rearrangement.

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