Question

How would you rank the following aromatic compounds in order of their reactivity in electrophilic aromatic substitution: anisole, nitrobenzene, acetophenone, toluene, and benzene?

Answer 1

To arrange the compounds in the increasing order of reactivity towards electrophile, we should be familiar with various phenomena like inductive effect, mesomeric effect. And we should know the influence of each substituent in the aromatic ring.

Complete answer:
So in the question, few aromatic compounds are given and we have to arrange those compounds in the increasing order of their reactivity towards the electrophile. To solve this question, we should have some basic ideas of a few phenomena like inductive effect, mesomeric effect, etc.
First, let us discuss the term electrophile. An electrophile is a chemical species that is electron loving. So electrophilic substitution means a substitution reaction that involves electrophilic substitution. Since the electrophile is an electron-loving species, it will attract or combine with a nucleophile, which is an electron ring species.
So we could say that electrophilic substitution will take place more easily with those species which have high electron density.
Now we have to discuss a few phenomena, which will give an idea about what factors favor electrophilic substitution.
The inductive effect explains how the electronegative atom attached to the aromatic ring will withdraw the electron density from the ring.
The mesomeric effect explains the electron density around the aromatic density by displacing the lone pairs present in the substituents.
The alkyl groups or hydrocarbyl groups also donate their electrons toward the ring, hence the ring will have high electron density.
The substituents in which the atoms like oxygen or nitrogen present, are more electronegative than C so the lone pairs of the neutral atoms get displaced towards the ring and increase the electron density of the ring.
But the groups like the nitro group, or the carbonyl groups with a positive charge on their carbon deactivates the ring. And the reaction with the electrophile will take place at a lesser rate.
So by analyzing these, we could conclude that the order of reactivity towards the electrophile will be :
Nitrobenzene > acetone > benzene > toluene > anisole.

Note:
In a covalent bond formed between two atoms with varying electronegativity, the electrons present in the bond will get displaced towards the most electronegative atom and that phenomenon is called the inductive effect.