The bond dissociation energy of B-F in BF3 is 646 kJmol^-1 whereas that of C-F in CF4 is 515 kJ

step 1 The bond dissociation energy of BF in BF3 is 646 kilojoules per mole, whereas that of carbon flo

The bond dissociation energy of B-F in BF3 is 646 kJmol^-1...

The bond dissociation energy of $\mathrm{B}-\mathrm{F}$ in $\mathrm{BF}_{3}$ is $646 \mathrm{kJmol}^{-1}$ whereas that of $\mathrm{C}-\mathrm{F}$ in $\mathrm{CF}_{4}$ is $515 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The correct reason for higher B-F bond dissociation energy as compared to that of C-F is: $\quad$ (a) smaller size of $\mathrm{B}$ atom as compared to that of $\mathrm{C}$ atom $\square$ (b) stronger $\sigma$ bond between $B$ and $F i n B F_{3}$ as compared to that between $\mathrm{C}$ and $\mathrm{F}$ in $\mathrm{CF}_{4}$ $\square$ (c) significant $p \pi-p \pi$ interaction between $\mathrm{B}$ and $\mathrm{F}$ in $\mathrm{BF}_{3}$ whereas there is no possibility of such interaction between $\mathrm{C}$ and $\mathrm{F}$ in $\mathrm{CF}_{4}$ $\square$ (d) lower degree of $p \pi-p \pi$ interaction between $\mathrm{B}$ and $\mathrm{F}$ in $\mathrm{BF}_{3}$ than that between $\mathrm{C}$ and $\mathrm{F}$ in $\mathrm{CF}_{4}$

The bond dissociation energy of $\mathrm{B}-\mathrm{F}$ in $\mathrm{BF}_{3}$ is $646 \mathrm{kJmol}^{-1}$ whereas that of $\mathrm{C}-\mathrm{F}$ in $\mathrm{CF}_{4}$ is $515 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The correct reason for higher B-F bond dissociation energy as compared to that of C-F is: $\quad$
(a) smaller size of $\mathrm{B}$ atom as compared to that of $\mathrm{C}$ atom $\square$
(b) stronger $\sigma$ bond between $B$ and $F i n B F_{3}$ as compared to that between $\mathrm{C}$ and $\mathrm{F}$ in $\mathrm{CF}_{4}$ $\square$
(c) significant $p \pi-p \pi$ interaction between $\mathrm{B}$ and $\mathrm{F}$ in $\mathrm{BF}_{3}$ whereas there is no possibility of such interaction between $\mathrm{C}$ and $\mathrm{F}$ in $\mathrm{CF}_{4}$ $\square$
(d) lower degree of $p \pi-p \pi$ interaction between $\mathrm{B}$ and $\mathrm{F}$ in $\mathrm{BF}_{3}$ than that between $\mathrm{C}$ and $\mathrm{F}$ in $\mathrm{CF}_{4}$

Key Concepts

Bond Dissociation Energy

Bond dissociation energy is a measure of the strength of a chemical bond, defined as the energy required to break a bond homolytically. It is fundamental to understanding reaction energetics, the stability of molecules, and the influence of electronic and steric factors on bond strength.

Pi Back Bonding

Pi back bonding (or p?–p? interaction) involves the donation of electron density from a filled p-orbital of one atom (usually an electronegative atom carrying lone pairs) into an empty p-orbital of an adjacent atom. This interaction can impart partial double bond character to a bond, thereby increasing its strength and bond dissociation energy.

Electronic Configuration and Electron Deficiency

Electronic configuration of the central atom plays a crucial role in bonding characteristics. Atoms with electron deficiency, such as boron in certain compounds, can accept electron density from surrounding ligands via their empty orbitals, facilitating additional bonding interactions (like back donation) that strengthen the bonds.

Orbital Overlap and Molecular Orbital Theory

Effective orbital overlap between bonding orbitals is essential for forming strong covalent bonds. Molecular orbital theory explains how the mixing of atomic orbitals forms bonding and antibonding molecular orbitals; the nature and extent of these overlaps, including sigma and pi interactions, determine the overall bond strength.

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