Question

Which of the following is not an electrophile?
A) $C{H_3}^ +$
B) $AIC{I_3}$
C) $Si{F_4}$
D) $\left[ {\left( {C{H_3}} \right){N^ + }} \right]OH{^ - }$

Answer 1

We have to know that electrophiles are atoms or molecules known to be electron deficient and that carry a partial (or fully) positive charge and will seek an electron pair to form a covalent bond. An example of an electrophile is a Lewis Acid.

Complete answer:
We need to remember that the strength of electrophile is given by its electrophilicity, which is the ability to attract electrons. Therefore, a positively charged species that requires electrons to obtain stability is a good and strong electrophile. We will look at all the options:
Option A) this option is incorrect as $C{H_3}^ +$ contains a sextet of electrons on carbon and requires two more to complete the octet. It is a powerful electrophile. While carbenes are neutral, the requirement of a single electron for octet completion lends them to act as electron-loving species.
Option B) this option is incorrect as an electrophile is deficient of electrons in nature. Therefore, according to the octet rule aluminum can accept two more electrons to have a total of eight electrons in the octet. Therefore, $AIC{I_3}$ is an electrophile.
Option C) this is an incorrect option as $Si{F_4}$ is an electrophile.

Option D) this option is correct as $\left[ {\left( {C{H_3}} \right){N^ + }} \right]OH{^ - }$ is neither an electrophile nor a nucleophile.

Note:
We have to remember that the nucleophiles are species that have a pair of electrons to donate, whilst electrophiles are species that either have a positive charge or are neutral but which have empty electron orbitals which are attracted to an electron rich centre.