Which of the following is least reactive toward complex formation with `BM_(3)` ?

Options

A. `NH_(3)`
B. `Me_(3)N`
C. `MeNH_(2)`
D. `Me_(2)NH`

Answer

B

Explanation

The correct order of complex formation is
`Me_(2)NH gt MeNH_(2) gt NH_(3) gt gt Me_(3)N`
The first three amines are in the expected order because replacing `H` s by electron-donating alky1 groups make the amines more nucleophilic However another factore appears when `Me_(3)N` is involved The methyl groups on `B` hindering close approach of the two molecules and facilitating dissociation of the complex, if formed The net result is a slight drop in the complexation of the `3^(@)` amine This type of steric hindrance is called front strain (F-strain),since the hindrane occurs in fornt of the approaching molecules