Grade 12th passOrganic Chemistry

Do Ortho chloro benzoicacid show
Ortho effect? Does methyl group only
Show Ortho effect?

Celestine

7 Years agoGrade 12th pass

Approved Tutor Answer7 Years ago

Due to ortho effect, in most cases, “Ortho-isomer of Benzoic acid is strongest acid as compared to simple benzoic acid or meta & para-isomers & Ortho- isomer of Aniline is Weakest Base as compared to simple aniline or meta & para-isomers.”
In case of ortho-substituted benzoic acids, due to steric inhibition, the -COOH group goes out of plane and hence decrease in resonance stabilisation of acid as compared to anion make it better acid.
Acidic Character order:
o-Bromobenzoic acid [3.1] > m-BromoBenzoic acid [3.93]> p-BromoBenzoic acid [4.1] > Benzoic acid [4.17]
o-ChloroBenzoic acid [2.89] > m-ChloroBenzoic acid [3.82]> p-ChloroBenzoic acid [3.98]> Benzoic acid [4.17]. Basicity implies tendency of protonation. In o-toluidine, methyl group exerts steric hindrance and avoid protonation which in turn makes it less basic as compared on aniline. On the other hand in o-touic acid, let us consider the acidic strength of ortho substituted and non substituted nearly equal but due to steric hindrance again tdency to loose electrons is more in unsubstituted making it less acidic as compared to substituted.Thus, overall it is supporting acidic nature.