Question

Which of the following is not electrophile?
(A)- ${\text{B}}{{\text{F}}_{\text{3}}}$
(B)- ${\text{H}}{{\text{g}}^{{\text{2 + }}}}$
(C)- ${\text{AlC}}{{\text{l}}_{\text{3}}}$
(D)- ${\text{N}}{{\text{H}}_{\text{3}}}$

Answer 1

Hint: Those species in which after binding with other atoms, the central atom still has extra electrons or lone pair of electrons present on it; will not accept incoming electrons easily and not behave as electrophile.

Complete answer:
Electrophiles are positively charged or electron deficient species, which accepts electrons from outside.
-In option (A) ${\text{B}}{{\text{F}}_{\text{3}}}$ is given, where Boron is the central atom whose atomic number is 5 & electronic configuration is $1{s^2},2{s^2}2{p^1}$. So, in the outermost shell 3 electrons are present which binds with three fluorine atoms. But still it behaves as electrophile to get stable or to get octet configuration.
-In option (B) ${\text{H}}{{\text{g}}^{{\text{2 + }}}}$ is given, which is already present in +2 oxidation state & behave as electrophile.
-In option (C) ${\text{AlC}}{{\text{l}}_{\text{3}}}$ is given, where Aluminium is the central atom whose atomic number is 13 & electronic configuration is $1{s^2},2{s^2}2{p^6},3{s^2}3{p^1}$. So, in the outermost shell 3 electrons are present which binds with three chlorine atoms. But still it behaves as electrophile to get stable or to get octet configuration.
-In option (D) ${\text{N}}{{\text{H}}_{\text{3}}}$ is given, where Nitrogen is the central atom whose atomic number is 7 & electronic configuration is $1{s^2},2{s^2}2{p^3}$. In the outermost shell of nitrogen 5 electrons are present, out of these 3 electrons bind with three chlorine atoms & two electrons are present as one lone pair on nitrogen. Due to the presence of these lone pairs of electron nitrogen will not behave as electrophile & accept electrons from outside.

Hence, option (D) is correct.

Note:
Here some of you may think that why ${\text{B}}{{\text{F}}_{\text{3}}}$ and ${\text{AlC}}{{\text{l}}_{\text{3}}}$is electrophile while they haven’t positive charge on it. So the reason is that any compound in which the outermost shell will not receive octet electronic configuration, they will accept electrons from outside.