Which of these is least likely to act as a Lewis base?
Which of these is least likely to act as a Lewis base?
$\mathrm{CO}$
$\mathrm{F}^{-}$
$\mathrm{BF}_3$
$\mathrm{PF}_3$
Solution
Electron rich species are called Lewis base. Among the given, $\mathrm{BF}_3$ is an electron deficient species, so have a capacity of electron accepting instead of donating that's why it is least likely to act as a Lewis base. It is a Lewis acid.