Question

Which of these is least likely to act as a Lewis base?

• A. $CO$
• B. $F^{-}$
• C. $B{F}_3$
• D. $P{F}_3$

Answer 1

The correct option is C $B{F}_3$

$CO$, $F^{-}$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.