Impedimento eléctrico y otros factores en la nitración de la 2-aminopiridina

The different isomer yields observed in many aromatic electrophilic substitution reactions can be explained by steric hindrance. However, this is not the case when there are drastic differences in the reaction yields of the isomeric products obtained. This is generally due to the presence of other factors, for instance, electric rejection between two positive charges in the reaction stage. Thus, a very important point to bear in mind is electric hindrance, a new theoretical concept. We have taken as an example 2-aminopyridine nitration. We provide an extended theory on this subject, which is in accordance with the observed regiochemistry and with the reaction yields of the isomeric products obtained. Dipole moments were also taken into account.

We discuss too the 2-nitraminopyridine rearrangement in acidic medium. The theoretical discussion is also in agreement with reported trans-nitration experimental results. Our proposals were also contrasted with the findings from thermolysis and photolysis carried out with 2- nitraminopyridine.