Question

Which of the following is least likely to behave as Lewis base?

• A. $O{H}^{-}$
• B. $H_{2}O$
• C. $N{H}_3$
• D. $B{F}_3$

Answer 1

Answer: (D)

$CO,F^{-}$and $P{F}_3$ can either donate a lone pair of electron or pi electrons. Hence, they act as Lewis bases.
On the other hand, $B{F}_3$ has vacant orbital in which it can accent a lone pair of electrons or pi electrons. Hence, it acts as a Lewis acid. Thus, it has least tendency to act as a Lewis base.