Inorganic Chemistry

Thanks decreasing order of power of boron halides to act as Lewis acids is ?

Kousalya Kousalya

6 Years agoGrade

2 Answers

Arun

Approved Tutor Answer6 Years ago

BI3>BBr3>BCl3>BF3.this trend is due to pie back bonding. All halides have lone pairs, they donate one lone pair to boron by overlapping with the p orbital of ..

Vikas TU

6 Years ago

Dear student

We know that the electronegativity of halogens decreases from fluorine to iodine as we move down the group. Hence, according to this, BF 3 should be the most Lewis acidic due to the electron withdrawing nature of fluorine atoms.

However, the order is just the opposite due to back-bonding. Back bonding due to the lone pair of electrons of halogen atom increases electron density on B centre, thereby, reducing its lewis acid character. This back bonding is more in case of BF3 due to similar size of orbitals of boron and fluorine atoms, whereas it decreases down the group due to the increasing size of orbitals as we move from F to I.