Question

Which of the following is an electrophilic reagent?
A. ${{\text{H}}_{\text{2}}}{\text{O}}$
B. ${\text{O}}{{\text{H}}^ - }$
C. ${\text{NO}}_2^ + $
D. None of these

Answer 1

Hint: The reagent having an affinity for electrons is known as an electrophilic reagent. The electron-deficient species works as an electrophilic reagent

Step by step answer:
The electrophilic reagent as the name indicates loves the electron because it lacks electrons.
Electrophilic reagents accept electrons to form bonds.
The following type of species works as electrophilic reagent:
-Species having incomplete octant.
-Species having a positive charge.
Carbene, nitrene, and free radical are examples of electrophilic reagents.
The octet of sulphur trioxide is complete and it does not have a positive charge even the sulphur trioxide is an electrophilic reagent because due to the presence of three highly electronegative oxygen atoms, sulphur atom gets a slightly positive charge.
In ${{\text{H}}_{\text{2}}}{\text{O}}$ molecule, the oxygen atoms has two lone pair so, it can donate electrons but cannot accept electrons so, ${{\text{H}}_{\text{2}}}{\text{O}}$ will not work as electrophilic reagent so, option (A) is incorrect.
In ${\text{O}}{{\text{H}}^ - }$molecule, the oxygen atoms has a negative charge so, it can donate electrons but cannot accept electrons so, ${\text{O}}{{\text{H}}^ - }$ will not work as electrophilic reagent so, option (B) is incorrect.
In ${\text{NO}}_2^ + $molecule, the nitrogen atom has a positive charge so, ${\text{NO}}_2^ +$ is electron deficient. It can accept electrons so, ${\text{NO}}_2^ + $ will work as an electrophilic reagent, so option (C) is incorrect.

Therefore, option (C) ${\text{NO}}_2^ + $ is correct.

Note: The species which can donate electrons works as a nucleophile. A nucleophile is a nucleus means positive charge loving species. The species which have lone pairs of electrons or negative charge are nucleophilic reagents.