Question

Why is Aluminium chloride a Lewis acid?

Answer 1

Aluminium Chloride:

1. Compound with the formula $AlC{l}_3$ is known as Aluminium chloride or Aluminium trichloride.
2. It is made up of Aluminium and Chlorine atoms in a 1:3 ratio.

Aluminium chloride as a Lewis acid

1. $AlC{l}_3$​ is an electron deficient compound and has 6 valence electrons in its outermost shell after bond.
2. Its acts as a Lewis acid because it can accept electrons.
3. $Al$ has vacant orbitals and is a strong electrophile due to the presence of high electron negative $Cl$ atoms which further reduces the electron density from the central atom, hence it accepts the electron from ammonia and behave like a Lewis Acid.