WHAT IS ORTHO EFFECT.

Dear Abhijeet,

There are several reactions that have ortho selectivity.

Electrophilic aromatic substitution:
Here the ortho effect could be explained three different ways:
1. Electron donating substituents increase electron density on the ring, specifically at the ortho and para positions, which makes the reaction faster.
2. Electron donating substituents have lone pairs which stabilize the carbocation intermediate.
3. Electron donating substituents stabilize the positive charge on the ring through an inductive dipole effect.

The Kolbe-Schmidt, aromatic Claisen, and Fries rearrangement reactions essentially operate the same way, but usually are not covered (if at all) until the second semester of organic chemistry.

The newest type of reaction is called "directed ortho metalation". Unless you are in an advanced organic synthesis, probably at the graduate level, you won't encounter this. The concept is easy to understand, but a little difficult to get to work in an undergraduate lab.

Is this what you were looking for?

Thank you.