Q.
The increasing order of nitration of the following compounds is :
6099
203
JEE MainJEE Main 2018Organic Chemistry – Some Basic Principles and Techniques
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Solution:
Nitration is an electrophilic substitution reaction. Substituents that increase the electron density on the benzene ring activate it towards the electrophilic substitution reaction. Substituent groups with unshared electron pairs on the atom adjacent to the benzene ring (e.g., amino, methoxy) are stronger activating groups than groups without unshared electron pairs (i.e., alkyl groups). Even though amine is strong activating group, it gets protonated in the presence of acid to form anilinium ion which is deactivating.
Hence, (I) would be less reactive than (III). Chlorine although contain unshared electron pairs, it is deactivating toward electrophilic aromatic substitution because of the electronegative effect of the halogens.