Question

The correct lewis acid order for boron halides is__________.

Answer 1

Boron halides:

1. Boron is an electron-deficient element. $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^1$is its electrical configuration. It forms ${\mathrm{BX}}_3$ by donating the three electrons in its valence shell to each halogen atom.
2. Because the boron atom is not surrounded by an octet of electrons, boron halides are electron-deficient compounds. They tend to operate as strong Lewis acids as a result of this ability, accepting electron pairs from bases to create stable acid-base adducts.
3. The smaller the halide atom, the more effective the back bonding and the less likely it is to take a pair of electrons, according to back bonding theory.
4. The capacity of back bonding reduces as the size of halides grows down the group, As a result, Boron's electron deficiency rises, and its Lewis acid character rises as well.
5. Increasing the size of halide ions is${\mathrm{F}}^{-}<{\mathrm{Cl}}^{-}<{\mathrm{Br}}^{-}<{\mathrm{I}}^{-}$. The smaller the size more is the back bonding, lesser is the lewis acidic character
6. The sequence of boron halide is ${\mathrm{BrI}}_3>{\mathrm{BBr}}_3>{\mathrm{BCl}}_3>{\mathrm{BF}}_3$

Therefore, the correct lewis acid order for boron halides is ${\mathrm{BrI}}_3>{\mathrm{BBr}}_3>{\mathrm{BCl}}_3>{\mathrm{BF}}_3$