Chemistry - Aromatic Hydrocarbon Question with Solution | TestHub
Benzene and other aromatic rings have tendency to undergo electrophilic aromatic substitution reactions and do not undergo electrophilic addition reactions like alkenes and alkynes. Monosubstituted benzenes undergo substitution reactions either faster or slower than benzene depending on the fact that whether the group is electron donating or electron withdrawing, respectively. The directive influence of a group is determined by the fact that the arenium formed by the attack of electrophile on a particular position is more stable than the arenium ion formed by attacking other positions. Side chain oxidation of benzene gives benzoic acid irrespective of the length or nature of the Side chain.
Rank the following compounds in the decreasing order of their reactivity towards electrophillic substitution.
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Answer:
Solution:
C₆H₅−ONa is most reactive towards electrophilic substitution as −O− strongly activates the benzene ring. C₆H₅−NHCOCH₃ is less reactive as the lone pair of electrons of the N-atom is partially available and hence moderately activates the benzene ring. The −CHCl₂ group of C₆H₅−CHCl₂ weakly deactivates the benzene ring, whereas the NH₃ group of C₆H₅−NH₃ strongly deactivates the benzene ring.