1. Lewis acid strength of Boron trihalides
Dr. S. Mangalaraj
Assistant Professor
Department of Chemistry
St. Joseph’s College (Autonomous)
Tiruchirappalli

2. Lewis acid. contain an empty orbital
Lewis acid contain an empty orbital tendency to accept a pair of electron

3. How do you say that BX3 is Lewis acid
empty p orbital X

4. Electronegativity attract bond pair of electrons towards itself
Electronegativity order of halogens F > Cl > Br
Therefore Lewis acid strength order suppose to be
BF3 > BCl3 > BBr3
But correct order of Boron trihalide as follows
BF3 < BCl3 < BBr3

5. Because of back bonding nature the Lewis acid strength of Boron trihalide as follows
BF3 < BCl3 < BBr3

6. Thank you