Consider the molecule 4-methoxy-4'-nitrobiphenyl. Four positions on the aromatic rings are labeled as follows: Position a : ortho to the - OCH ₃ group Position b : meta to the - OCH ₃ group Position c : ortho to the - NO ₂ group Position d : meta to the - NO ₂ group During an electrophilic aromatic substitution reaction, the incoming electrophile will predominantly attack at:

Step-by-step solution

The molecule 4-methoxy-4'-nitrobiphenyl consists of two phenyl rings connected to each other. One ring has an electron-donating - OCH ₃ group, and the other has an electron-withdrawing - NO ₂ group. The - OCH ₃ group activates its attached ring towards electrophilic attack via a strong +M effect. Conversely, the - NO ₂ group strongly deactivates its attached ring via a -M effect. Therefore, electrophilic attack will occur preferentially on the more electron-rich ring, which is the one bearing the - OCH ₃ group. The