Select correct statements(s):a)― NO2 group activates benzene nuc...
Explanation:
To understand whether NO2 or NH2 group activates benzene nucleus for the attack of an electrophile at ortho- and para-sites, we need to consider the electron-donating or electron-withdrawing nature of these groups.
NO2 Group:
The NO2 group is a strong electron-withdrawing group due to the presence of the highly electronegative nitrogen and oxygen atoms. This group withdraws electron density from the benzene ring through resonance effects. As a result, the benzene ring becomes electron-deficient, making it less reactive towards electrophilic attack. Hence, the NO2 group deactivates the benzene nucleus towards electrophilic substitution reactions.
NH2 Group:
The NH2 group is a moderately strong electron-donating group due to the presence of the lone pair of electrons on the nitrogen atom. This lone pair of electrons can donate electron density to the benzene ring through resonance effects. As a result, the benzene ring becomes electron-rich, making it more reactive towards electrophilic attack. Hence, the NH2 group activates the benzene nucleus towards electrophilic substitution reactions.
Conclusion:
Based on the above explanations, the correct statement is:
b) NH2 group activates the benzene nucleus for the attack of an electrophile at ortho- and para-sites.
This is because the NH2 group is an electron-donating group that increases the electron density on the benzene ring, making it more susceptible to electrophilic attack at the ortho- and para-positions. On the other hand, the NO2 group is an electron-withdrawing group that decreases the electron density on the benzene ring, making it less reactive towards electrophilic attack.