Question

The main factor responsible for weak acidic nature of $B-F$ bonds in $B{F}_3$ is:

• A. large electronegativity of F
• B. three centred two electron bonds in $B{F}_3$
• C. $p\pi$ - $d\pi$ back bonding
• D. $p\pi$ - $p\pi$ back bonding

Answer 1

The correct option is D $p\pi$ - $p\pi$ back bonding

As refer to the above image, in $B{F}_3$ boron atom accepts the lone pairs of fluorine to form $p^{\pi }-p^{\pi }$ back bonding. Hence, its Lewis acidic character is decreased.