106yup :) that is what i had in mind
Q. Give an example where ortho-substituted benzoic acid is NOT stronger than benzoic acid.. i.e. where ortho effect is not applicable
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4 Answers
49the benzoic acid with -NH2 in the ortho position has Ka value 1.6 x 10-5.
Benzoic acid has Ka value 6.3 x 10-5.
so ortho effect not applicable.
39The ortho effect actually DOES apply, not as a steric inhibition of resonance (SIR) on -COOH but as a steric inhibition of protonation (SIP) on -NH2. The aniline cannot be protonated easily as it is thrown out of the plane of the benzene ring by the bulkiness of -COOH (terminating the resonance connection). So the protonated aniline would not be stable, and does not form. This makes the -NH2 group less basic than if it were a para or meta isomer.
So it doesn't apply on -COOH (which is what Asish has asked) but it applies on the amino group nevertheless.
