Question

Among boron halides, which is the strongest Lewis is acid?

• A. $B{F}_3$
• B. $B{l}_3$
• C. $BC{l}_3$
• D. $BB{r}_3$

Answer 1

The correct option is B $B{l}_3$

Among boron halides, $B{I}_3$ is the strongest Lewis is acid. The decreasing order of Lewis acidity of boron halides is $B{I}_3>BB{r}_3>BC{l}_3>B{F}_3$.

This order is due to the relative tendency of the halogen atom to back donate its unutilised electrons to the vacant p-orbitals of B atoms.

Hence, option $B$ is correct.