Question

what is ortho effect ?

Answer 1

The ortho effect is the phenomenon where a substituent located at the ortho position of an aromatic ring (especially in benzoic acids or anilines) enhances or alters the molecule’s acidity or basicity compared to its meta and para isomers, primarily due to steric hindrance, disrupted resonance, and polar interactions.

Answer 2

Key Points:

1. Definition: The ortho effect arises when a substituent at the ortho position (adjacent to a functional group like –COOH or –NH₂) causes changes in acidity or basicity beyond what is seen in meta or para isomers.
2. Steric Hindrance: An ortho substituent creates steric strain, twisting the carboxyl or amino group out of the aromatic plane and reducing resonance stabilization.
3. Acidity Increase: In ortho‑substituted benzoic acids, reduced resonance means the carboxylate anion is less delocalized, so the acid is stronger.
4. Basicity Decrease: In ortho‑substituted anilines, the amino lone pair is less conjugated with the ring, decreasing basicity.
5. Independence of Substituent Type: Both electron‑donating and electron‑withdrawing groups at ortho position can produce this effect due to steric and polar factors.