EAS reactivity. I am comparing two benzene rings. One has an NO2 group attached to it and the other has a C(=0)CH3 attached to it. I understand they are both deactivating groups so they are low in reactivity but how do I know which of the two is the least reactive?
To determine which of the two groups, the NO2 group or the C(=0)CH3 group, is the least reactive, you can assess their electron-withdrawing abilities by examining their inductive effects and resonance effects.
1. Inductive Effect:
The inductive effect is the electron-withdrawing or electron-donating ability of a functional group in a molecule. In general, the more electronegative an atom is, the stronger its inductive effect. Comparing the NO2 group and the C(=0)CH3 group, nitrogen (N) in the NO2 group is more electronegative than carbon (C) in the C(=0)CH3 group. Thus, the NO2 group exhibits a stronger inductive effect than the C(=0)CH3 group.
2. Resonance Effect:
The resonance effect occurs when electron delocalization happens within a molecule, influencing its reactivity. The NO2 group has resonance structures where the negative charge can be distributed across the entire group, making it highly electron-withdrawing. On the other hand, the C(=0)CH3 group has a resonance structure where the negative charge can only be localized on the oxygen atom due to the double bond. Therefore, the NO2 group exerts a stronger resonance effect than the C(=0)CH3 group.
Considering both the inductive and resonance effects, the NO2 group is more reactive and more strongly deactivating than the C(=0)CH3 group. Consequently, the benzene ring with the NO2 group attached to it is less reactive compared to the benzene ring with the C(=0)CH3 group attached to it.