Answer to Question #152922 in Organic Chemistry for nur

Question

Explain which one of these (anisole or benzaldehyde) will react faster
in nitration reaction.

Answer 1

Generally, Aromatic Electrophilic Substitution (AES) reaction rate will be faster for that aromatic compound in which there is an electron donating group (EDG) or comparatively more electron donating group (EDG) present in the benzene moiety. Nitration reaction is also AES reaction. Let us concentrate in the following figure.

In anisole, although O atom is more electronegative than C atom, but its lone pair is used to stabilize the adjacent positive charge through resonance. This is why OCH₃ group is called resonance donating group. And in benzaldehyde, there is CHO group which is electron withdrawing group (EWG). So the stability of I > II.

That is why Anisole bearing EDG shows faster nitration reaction than Benzaldehyde bearing EWG.