The bond dissociation energy of `B-F` bond in `BF_3` is `kJmol^(-1)` whereas that of `C-F` in `CF_4` is `515kJmol^(-1)`. The correct reason for higher `B-F` bond dissociation energy as compared to that of `C-F` is

Options

A. lower degree of ppi-ppi interaction between B and F in `BF_3` than that between C and F
B. significant ppi-p pi interaction between B and F in `BF_3` whereas there is no possibility of such interaction between C and F in `CF_4`
C. stonger `sigma` bond between B and F in `BF_3` as compared to that between C and F in `CF_4`
D. smaller size of `B` atom as compared to that of C atom.

Answer

B

Explanation

In `BF_3`, the octet of B is not complete. Thus, to get rid of electron deficiency, the empty `2p_z` orbital on B atom over-laps (side-on) with a full `2p_z` orbital on all the three F atoms (delocalized `ppi-ppi` backbonding):