Question

Which of the following has the highest nucleophilicity?
A.${{F}^{-}}$
B.$O{{H}^{-}}$
C.$C{{H}_{3}}^{-}$
D.$N{{H}_{2}}^{-}$

Answer 1

Hint: Halides are known to be more electrophilic, the substance which has excess electrons and is eager to donate pairs of electrons should exhibit the maximum nucleophilicity.

Complete answer:
In order to answer our question, we need to learn about nucleophiles and electrophiles. They are chemical species which can be used to accept, or donate electrons or a pair of electrons, so that a new chemical bond can be formed. Nucleophiles are those which usually give out, or donate an electron pair, whereas electrophiles are those which accept electron pairs, as they themselves are deficient or lacking in the number of electrons to fill the octet.
Electrophiles are usually positively charged and nucleophiles are negatively charged, and may consist of a lone pair or neutral electrons, so we can say that they are electron rich, and electrophiles are electron deficient.
Now, let us come to our question. We know that electrophilicity and nucleophilicity are opposite character traits. A substance which is more nucleophilic will obviously be less electrophilic, and vice versa. With the help of this concept we will solve the question. Clearly we can observe that $C{{H}_{3}}^{-}$ consists of excess electrons, or is electron rich. So, it is considered the maximum nucleophilic among the four options. After that comes $N{{H}_{2}}^{-}$ which still has some electrons available for donation. It is followed by $O{{H}^{-}}$ and ${{F}^{-}}$ respectively. The final order of nucleophilicity is given below:
$C{{H}_{3}}^{-}>N{{H}_{2}}^{-}>O{{H}^{-}}>{{F}^{-}}$

So, we obtain option C as the correct answer.

Note:
Some examples of electrophiles are ${{H}_{3}}{{O}^{+}},AlC{{l}_{3}}$, and the halogens. Nucleophiles and electrophiles play a major role in the substitution reactions.