Question

4. The pKa values of the ortho, para, and meta substituted benzoic acids are shown below. Use words and drawings to explain these relative acidities. (7 points) Ноо HOO HOO NH2 V NH2 NH2 pka = 4.89 pka = 4.95 pka = 4.73

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Answer 1

Less the pKa, more the acidity of the compound.

1-NH₂ group is group is having tm & I effect, matmen tm is Electrons Donating tmo is a resonating effec ffect, mamedomeric Effect & I + Induction effect. Bono Donating Effect while -I is electron withdrawing effect mating effect and - I io Inductive effect. Therefore mesomeric effect always dominateo Anductive effect Mesomeric effect only Election withdrawing effect gfect only acts on otthe and para positions. drawing Effect of a group increases acidity while Electron Donating Effect of a group decreased addity LOH C-OH NH2 NHZ NH2 tm &-a tm & -t only -t Buerall, Electron Effect Tonating Electron Withdrawing Effect Overall Effect Electron - Donating So Acidity of ② will be maximum Now Compariscon blw 08 :: In Oir i H-bonding (hydrogen Bonding) H So it will not be easily released as compared to -0H, X MTH In ® :- Jhere is no intra molecular H- bonding like 0 Therefore, Acidity of 6 7 Acidity of Finale Order - 0 < < < © of Acidity