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JEE Main 202628 JanuaryMorning Shift
Exam
JEE Main
Year
2026
Date
28 January
Shift
Morning Shift
Subject
Chemistry
Chapter
General Organic Chemistry

JEE Main 2026 · 28 January · Morning Shift · Chemistry · General Organic Chemistry

CORRECT order of stability for the following is CH_ 2 =CH^ - , CH_...

CORRECT order of stability for the following is CH2=CH−,CH3−CH2−,CH≡C−\mathrm{CH}_{2}=\mathrm{CH}^{-}, \mathrm{CH}_{3}-\mathrm{CH}_{2}^{-}, \mathrm{CH} \equiv \mathrm{C}^{-}

Options

  1. ACH2=CH−>CH≡C−>CH3−CH2−\mathrm{CH}_{2}=\mathrm{CH}^{-}>\mathrm{CH} \equiv \mathrm{C}^{-}>\mathrm{CH}_{3}-\mathrm{CH}_{2}^{-}
  2. BCH≡C−>CH2=CH−>CH3−CH2−\mathrm{CH} \equiv \mathrm{C}^{-}>\mathrm{CH}_{2}=\mathrm{CH}^{-}>\mathrm{CH}_{3}-\mathrm{CH}_{2}^{-}
  3. CCH≡C−>CH3−CH2−>CH2=CH−\mathrm{CH} \equiv \mathrm{C}^{-}>\mathrm{CH}_{3}-\mathrm{CH}_{2}^{-}>\mathrm{CH}_{2}=\mathrm{CH}^{-}
  4. DCH3−CH2−>CH2=CH−>CH≡C−\mathrm{CH}_{3}-\mathrm{CH}_{2}^{-}>\mathrm{CH}_{2}=\mathrm{CH}^{-}>\mathrm{CH} \equiv \mathrm{C}^{-}

Correct answer

B. CH≡C−>CH2=CH−>CH3−CH2−\mathrm{CH} \equiv \mathrm{C}^{-}>\mathrm{CH}_{2}=\mathrm{CH}^{-}>\mathrm{CH}_{3}-\mathrm{CH}_{2}^{-}

Step-by-step solution

Carbanion stability is determined by the s-character of the hybrid orbital bearing the negative charge.
The acetylide anion CH≡C−CH \equiv C^- has the carbanion on an sp hybridized carbon (50% s-character), providing optimal stabilization through efficient overlap with the charged orbital.
The vinyl anion CH2=CH−CH_2 = CH^- has the carbanion on an sp² hybridized carbon (33% s-character), offering moderate stabilization.
The primary alkyl anion CH3−CH2−CH_3 - CH_2^- has the carbanion on an sp³ hybridized carbon (25% s-character), providing the least stabilization.
Greater s-character enables better penetration of the nucleus and enhanced stabilization of the negative charge.
Therefore, the order is CH≡C−>CH2=CH−>CH3−CH2−CH \equiv C^- > CH_2 = CH^- > CH_3 - CH_2^-.
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