Question

A reaction between ammonia and boron trifluoride is given below: $N{H}_3+B{F}_3\to H_{3}N:B{F}_3$ Identify the acid and base in this reaction. Which theory explains it? What is the hybridization of $B$ and $N$ in the reactants?

Answer 1

$N{H}_3+B{F}_3\to H_{3}N:B{F}_3$

From the reaction it is clear that $B{F}_3$ is accepting the electron pairs from :$N{H}_3$.

Although $B{F}_3$ does not have a proton but acts as Lewis’s acid as it is an electron deficient compound.

It reacts with $N{H}_3$ by accepting the lone pair of electrons from $N{H}_3$, forming a co-ordinate bond and completes its octet.

Acids are electron pair acceptor and bases are electron pair donors. So, $B{F}_3$ is a Lewis acid and $N{H}_3$ is a Lewis base.

So, Lewis theory of acids and bases explains it.

Hybridization

Boron in $B{F}_3$ is $s{p}^2$ hybridized- as 3 orbitals i.e. $2s,2px,2py$ gets involved in bond formation.

whereas $N$ in $N{H}_3$ is $s{p}^3$ hybridized with 4 orbitals - $2s,2px,2py,2pz$ involved .