Chemical Bonding And Molecular Structure

  • Question
    CBSEENCH11008125

    The bond dissociation energy of B–F in BF3 is 646 kJ 1 mol whereas that of C-F in CF4 is 515 kJ 1 mol.The correct reason for higher B-F bond dissociation energy as compared to that of C-F is

    • Smaller size of B-atom as compared to that of C- atom

    • Stronger σ bond between B and F in BF3 as compared to that between C and F in CF4

    • Significant pπ - pπ interaction between B and F in BF whereas there is no possibility of such 3 interaction between C and F in CF4 

    • lower degree of pπ - pπ interaction between B and F in BF3 than that between C and F in CF4

    Solution

    C.

    Significant pπ - pπ interaction between B and F in BF whereas there is no possibility of such 3 interaction between C and F in CF4 

    B has vacant available p orbital and hence it involves pπ - pπ back bonding which is not possible in CF4 as C does not have vacant orbital. 

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