Practice problem
Friday, January 23, 2015
9:59 PM
Both groups have a strong inductive effect. Both are electron withdrawing and destabilize the cation.
The inductive effect comes from the presence of the highly electronnegative fluorin atoms. CF3 has
more fluorines and is more destabilizing.
Only the inductive effect. Both are electron withdrawing. Fluoride more electron negative and that's why it
has a stronger destabilizing effect.
NO2 has a strong resonance and inductive electron withdrawing effect. CF3 has strong inductive effect.
Resonance + induction is stronger effect than just induction with CF3. Negative charge is stabilized by electron
withdrawing groups. Draw a resonance structure that shows that NO2 is electron-withdrawing by resonance.
In the molecule on the right there is an inductive effect but because of the double bond there is also a
resonance effect (draw a resonance structure for that). In the molecule on the left there is only an inductive
effect. There is simply no pi connection between the NO2 group and the anion. Overall, resonance + inductive
effect is stronger than just the inductive effect and the one on the left is more stable.
There is a strong resonance effect and strong inductive effect whan NO2 is in the para position. There is only
and inductive effect in meta position. In meta position there is no way to delocalize the negative charge from
the phenol into the NO2 group. In para isomer there is.
OMe exerts both inductive and resonance effects when in para position relative to the Cl. Resonance is
strongly donating and inductive is a weaker electron withdrawing. In meta position OMe can only exert
an inductive effect. See lecture notes for more details.
This is exactly the same as for the Cl that we did for in lecture. In para position fluoride is a weak resonance
donor and strong inductive acceptor. In meta position it is just a strong inductive acceptor. F is weaker
accceptor in meta position than in ortho or para but resonance in ortho and para compensates for that. So
overall inductive acceptor + resonance donor is better for the cation than just acceptor.
There is no conjugation between the ester on the benzene ring and the anoin on the oxygen. There is however an inductive
effect. It is stronger in para position because of the following resonance structure:
The electrons from the anion are not in conjugation with the aromatic ring. So there is only an inductive effect. OMe in the
ortho position has a stronger inductive effect as it is closer to the anion.
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