Question

Classify `BX_3`, `"water"`, `"ammonia"`, `"alcohols"`, as electrophiles or nucleophiles?

Answer 1

`"Boron trichloride is an electrophile..........."`

Explanation:

Ammonia, water, and alcohols, are all potential nucleophiles due to the lone pair(s) of electrons on the nitrogen or oxygen atoms.

On the other hand, the boron centre in `BCl_3` is sextet rather than octet, and as a result boron trichloride is a potent electrophile, i.e. it accepts electron density.

Much of the chemistry of `BX_3` may be rationalized by this Lewis acidity; the propensity of boron to react with a donor atom to form `""^(-)BX_3X'^` species.