Which of the following compounds would be least reactive toward electrophilic substitution?
A)I
B)II
C)III
D)IV

Question

Which of the following compounds would be least reactive toward electrophilic substitution? 
A)I 
B)II 
C)III 
D)IV

Quizplus · Accepted Answer

The reactivity of an aromatic compound towards electrophilic substitution depends on the ability of the ring to donate electrons to the incoming electrophile. Compounds with electron-donating substituents (e.g. -OH, -NH2, -CH3) are more reactive, while those with electron-withdrawing substituents (e.g. -NO2, -COOH, -CN) are less reactive. 
In this case, compound II has a nitro group (-NO2) which strongly withdraws electrons from the ring, decreasing its reactivity towards electrophilic substitution. Therefore, it is the least reactive among the five choices.

Which of the Following Compounds Would Be Least Reactive Toward