While heavily halogenated carbanions are stabilized by inductive effects, why is the trichloromethyl carbanion () significantly more stable than the trifluoromethyl carbanion (), despite fluorine bein

Question

While heavily halogenated carbanions are stabilized by inductive effects, why is the trichloromethyl carbanion ($CCl_3^-$) significantly more stable than the trifluoromethyl carbanion ($CF_3^-$), despite fluorine being more electronegative?

Prashant Kotian · Accepted Answer

Correct answer: C. Although F has a stronger effect, Cl possesses vacant 3d orbitals. The negative charge on the carbon atom can delocalize into these vacant d-orbitals of adjacent chlorine atoms via back-bonding (resonance), providing substantial stabilization unavailable to .

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