Although boron trifluoride adds on trimethylamine but it does not add on triphenylamine. Explain.

Explanation

Trimethylamine has three electron donating alkyl groups and therefore acts as a Lewis base and reacts with `BF^(3)`
(a Lewis acid).
`underset("Trimethylamine")(CH_(3)-underset(CH_(3))underset(|)overset(CH_(3))overset(|)(N: ))` `underset("Trimethylamine")(C_(6)H_(5)-underset(C_(6)H_(5))underset(|)overset(C_(6)H_(5))overset(|)(N: ))`
On the other hand, in triphenylamine, the lone pair of N gets delocalised over three benzene rings. Thus, the lone pair is not readily available to `BF_(3)` for reaction.