Ortho effect is an organic chemistry phenomenon where the presence of an chemical group at the at ortho position or the 1 and 2 position of a phenyl ring, relative to the carboxylic compound changes the chemical properties of the compound.   This is caused by steric effects and bonding interactions along with polar effects caused by the various substituents which are in a given molecule, resulting in changes in its chemical and physical properties. The ortho effect is associated with substituted benzene compounds.
There are three main ortho effects in substituted benzene compounds:
* Steric hindrance forces cause substitution of a chemical group in the ortho position of benzoic acids become stronger acids.
* Steric Inhibition of Protonation caused by substitution of anilines to become weaker bases, compared to substitution of isomers in the meta and para position.
* Electrophilic aromatic substitution of disubstituted benzene compounds causes steric effects which determines the regioselectivity of an incoming electrophile in disubstituted benzene compounds