Question

Which of the following is an electrophilic reagent ?

1) ROH 2) BF₃ 3)NH₃ 4)RO^-

Answer 1

Answer is optn (B) BF3
Lewis acids are by definition electrophiles. Electrophiles love electrons, or negative charge. Boron has an empty 2p orbital and there exists a strong partial positive charge on the boron due to the extremely electronegative fluorine atoms covalently bound to boron. This strong partial positive character, coupled with a vacant orbital, makes BF3 a potent Lewis acid and thus an electrophile.